The Effect of Sildenafil and Tadalafil on Skeletal Muscle and Perceptual Fatigue

• Sponsor: The University of Texas Medical Branch, Galveston (Other)
• Overall Status: Completed
• CT.gov ID: NCT01661595
• Collaborator: (none)
• Enrollment: 30
• Location: 1
• Arms: 4
• Duration (Months): 30.9
• Patients Per Site Per Month: 1

Study Details

Study Description

Brief Summary

This study is funded by the Moody Endowment. In this project, we will investigate the potential effect of skeletal muscle nitric oxide (NO) production on skeletal muscle anabolism, muscle strength, physical function, and body composition in older individuals. Further, we will determine whether augmentation of NO-mediated signaling reduces fatigue and fatigability.

Condition or Disease	Intervention/Treatment	Phase
Fatigue	Drug: Sildenafil; Drug: tadalafil; Drug: Placebo	N/A

Detailed Description

The Investigators hypothesize that upregulation of skeletal muscle NO-cGMP mediated responses through phosphodiesterase (PDE) inhibition by sildenafil or tadalafil causes an acute anabolic response of skeletal muscle protein synthesis. NO is well-known to elicit vasodilation through stimulation of cGMP signaling, and NO-mediated changes in muscle perfusion may influence both skeletal muscle anabolism and perceptual fatigue. To measure skeletal muscle protein synthesis, we will infuse a stable isotope tracer of phenylalanine and measure its incorporation into skeletal muscle proteins following a dose of sildenafil, tadalafil, or placebo. The Investigators will also determine whether differences exist between men and women in response to PDE inhibition. As skeletal muscle NO-cGMP signaling has been implicated in fatigue responses, we will assess the acute effect of sildenafil and tadalafil on fatigue. Fatigue can be manifested both as a performance deficit at a local level (e.g., a reduced ability of skeletal muscle to produce power or force) as well as a subjective experience of lacking physical or mental energy. Accordingly, we will use more than one means (skeletal muscle performance, fatigue questionnaires, accelerometers) to study fatigue. The Investigators hypothesize that sildenafil or tadalafil will acutely reduce exercise-associated fatigability and skeletal muscle fatigue development

Study Design

• Study Type: Interventional
• Actual Enrollment: 30 participants
• Allocation: Randomized
• Intervention Model: Crossover Assignment
• Intervention Model Description: Subjects were assigned to one of 4 arms: Sildenafil (50mg/day) for weeks 0-4. Placebo for weeks 5-8. Tadalafil (10mg/day) for weeks 0-4. Placebo for weeks 5-8. Placebo for weeks 0-4. Sildenafil (50mg/day) for weeks 5-8. Placebo for weeks 0-4. Tadalafil (10mg/day) for weeks 5-8.Subjects were assigned to one of 4 arms:Sildenafil (50mg/day) for weeks 0-4. Placebo for weeks 5-8. Tadalafil (10mg/day) for weeks 0-4. Placebo for weeks 5-8. Placebo for weeks 0-4. Sildenafil (50mg/day) for weeks 5-8. Placebo for weeks 0-4. Tadalafil (10mg/day) for weeks 5-8.
• Masking: Triple (Participant, Care Provider, Investigator)
• Primary Purpose: Treatment
• Official Title: The Effect of Sildenafil and Tadalafil on Skeletal Muscle and Perceptual Fatigue.
• Study Start Date: Nov 1, 2012
• Actual Primary Completion Date: Jun 1, 2015
• Actual Study Completion Date: Jun 1, 2015

Arms and Interventions

Arm	Intervention/Treatment
Active Comparator: Sildenafil / Placebo 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8.	Drug: Sildenafil; 50 mg/day for 4 weeks; Other Names: Viagra Revatio ; Drug: Placebo; Placebo 1 capsule per day for four weeks.
Active Comparator: Tadalafil / Placebo 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8.	Drug: tadalafil; 10 mg/day for 4 weeks.; Other Names: Cialis Adcirca ; Drug: Placebo; Placebo 1 capsule per day for four weeks.
Active Comparator: Placebo / Sildenafil Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8.	Drug: Sildenafil; 50 mg/day for 4 weeks; Other Names: Viagra Revatio ; Drug: Placebo; Placebo 1 capsule per day for four weeks.
Active Comparator: Placebo / Tadalafil Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8.	Drug: tadalafil; 10 mg/day for 4 weeks.; Other Names: Cialis Adcirca ; Drug: Placebo; Placebo 1 capsule per day for four weeks.

Outcome Measures

Primary Outcome Measures

1. Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Placebo [after 4 weeks of placebo]

   Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks.

2. Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Active Drug [after 4 weeks of active drug]

   Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks.

3. Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Placebo [after 4 weeks of placebo]

   The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test after 4 weeks of placebo. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue.

4. Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Active Drug [after 4 weeks of active drug]

   The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue.

Secondary Outcome Measures

1. Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo [after 4 weeks of placebo]

   Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

2. Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug. [after 4 weeks of active drug]

   Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

3. Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo. [after 4 weeks of placebo]

   Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

4. Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug [after 4 weeks of active drug]

   Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

5. Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0. [week 0]

   Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

6. Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4. [week 4]

   Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

7. Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8. [week 8]

   Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

8. Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0. [week 0]

   Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

9. Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4. [week 4]

   Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

10. Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8. [week 8]

    Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.

11. Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Placebo [after 4 weeks of placebo]

    Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

12. Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Active Drug [after 4 weeks of active drug]

    Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.

13. Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 0 [Week 0]

    Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.

14. Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 4 [week 4]

    Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.

15. Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 8 [week 8]

    Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.

Other Outcome Measures

1. Hemoglobin Level at Week 0 [week 0]

   Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.

2. Hemoglobin Level Measured at Week 4 [week 4]

   Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.

3. Hemoglobin Level Measured at Week 8 [week 8]

   Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.

4. Hematocrit Level Measured at Week 0 [week 0]

   Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.

5. Hematocrit Level Was Measured at 4 Weeks [4 weeks]

   Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.

6. Hematocrit Level Measured at Week 8 [week 8]

   Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.

Eligibility Criteria

Criteria

• Ages Eligible for Study: 50 Years to 60 Years
• Sexes Eligible for Study: All
• Accepts Healthy Volunteers: Yes

Inclusion Criteria:

1. Age 50-60 years of age

2. Ability to sign consent form (score>23 on the 30-item Mini Mental Status examination, MMSE)

3. Stable body weight for at least three months.

Exclusion Criteria:

1. Physical dependence or frailty (impairment in any of the Activities of Daily Living (ADL), history of falls (>2/year) or significant weight loss in the past year).

2. Pregnancy

3. Significant heart, liver, kidney, blood or respiratory disease.

4. Peripheral vascular disease.

5. Diabetes mellitus or other untreated endocrine disease.

6. Active cancer

7. Use of nitrates.

8. Recent (within 6 months) treatment with anabolic steroids, or corticosteroids.

9. Alcohol or drug abuse.

10. Severe depression (>5 on the 15-item Geriatric Depression Scale, GDS).

11. Cardiac abnormalities such as cardiac shunt or previously diagnosed pulmonary hypertension.

12. Systolic blood pressure <100 or>150, diastolic blood pressure <60 or 90>. This range is smaller than the acceptable range stated in the prescribing information for sildenafil/tadalafil (90/50 and <170/110).

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	University of Texas Medical Branch	Galveston	Texas	United States	77555-0361

Sponsors and Collaborators

• The University of Texas Medical Branch, Galveston

Investigators

• Principal Investigator: Melinda Sheffield-Moore, PhD, University of Texas Medical Branch, Galveston

Study Documents (Full-Text)

None provided.

More Information

Publications

None provided.

• Responsible Party: The University of Texas Medical Branch, Galveston
• ClinicalTrials.gov Identifier: NCT01661595
• Other Study ID Numbers: 12-153
• First Posted: Aug 9, 2012
• Last Update Posted: Jul 17, 2018
• Last Verified: Apr 1, 2018

• Keywords provided by The University of Texas Medical Branch, Galveston: Fatigue; Fatigability; Surface Electromyography (sEMG); cyclic guanosine monophosphate (cGMP); Nitric Oxide (NO); NO-cGMP; Phosphodiesterase (PDE); Sildenafil; Tadalafil; Isotope; Infusion; Anabolism; Upregulation; Accelerometer; Placebo; Nitrosylation
• Additional relevant MeSH terms: Fatigue; Sildenafil Citrate; Tadalafil

Study Results

Participant Flow

Recruitment Details	Participants were recruited from the community via flyers and local postings.
Pre-assignment Detail	30 subjects enrolled in this study. 6 subjects failed the screening and were withdrawn. 6 subjects chose to withdraw participation before the study began. 18 subjects began the study. 2 subjects were withdrawn during the study. 16 subjects completed the study.

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Period Title: Phase 1: Week 0-4
STARTED	5	4	5	4
COMPLETED	4	4	5	4
NOT COMPLETED	1	0	0	0
Period Title: Phase 1: Week 0-4
STARTED	4	4	5	4
COMPLETED	4	4	4	4
NOT COMPLETED	0	0	1	0

Baseline Characteristics

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil	Total
Arm/Group Description	Sildenafil (50mg/day) daily for weeks 0-4, then Placebo daily weeks 5-8.	Tadalafil (10mg/day) daily for weeks 0-4, then Placebo daily for weeks 5-8.	Placebo daily for weeks 0-4, then Sildenafil (50mg/day) daily for weeks 5-8.	Placebo daily for weeks 0-4, then Tadalafil (10mg/day) daily for weeks 5-8.	Total of all reporting groups
Overall Participants	5	4	5	4	18
Age (years) [Mean (Standard Deviation) ]
Mean (Standard Deviation) [years]	53.6 (4.16)	56 (1.41)	52.4 (1.51)	57.25 (2.99)	54.6 (3.22)
Sex: Female, Male (Count of Participants)
Female	4 80%	4 100%	3 60%	2 50%	13 72.2%
Male	1 20%	0 0%	2 40%	2 50%	5 27.8%
Region of Enrollment (Count of Participants)
United States	5 100%	4 100%	5 100%	4 100%	18 100%

Outcome Measures

1. Primary Outcome

Title	Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Placebo
Description	Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks.
Time Frame	after 4 weeks of placebo

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalafil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	59.69 (33.71)	42.07 (5.19)	67.17 (26.87)	63.24 (8.34)

2. Primary Outcome

Title	Skeletal Muscle Fatigue as Measured by Biodex 4 Pro After 4 Weeks of Active Drug
Description	Isokinetic Fatigue Measure (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 50 contractions were performed at 100% force, one contraction every second. Isokinetic fatigue will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug. Data is presented as mean maximum force over all 50 kicks.
Time Frame	after 4 weeks of active drug

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil / Placebo	Tadalafil / Placebo	Placebo / Sildenafil	Placebo / Tadalafil
Arm/Group Description	50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	60.90 (35.60)	42.48 (6.30)	62.68 (24.88)	63.25 (15.12)

3. Primary Outcome

Title	Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Placebo
Description	The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test after 4 weeks of placebo. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue.
Time Frame	after 4 weeks of placebo

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil / Placebo	Tadalafil / Placebo	Placebo / Sildenafil	Placebo / Tadalafil
Arm/Group Description	50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [units on a scale]	4.33 (1.53)	2.5 (0.58)	7.0 (1.83)	4.75 (0.96)

4. Primary Outcome

Title	Exercised Induced Fatigability as Measured by Fatigue Rating Scale After 4 Weeks of Active Drug
Description	The fatigue rating scale is a scale from 0 to 10 with 0 being no fatigue at all and 10 being the worst fatigue the subject can imagine. The subject is asked to rate their level of fatigue in their leg. This test was performed before and immedicately after the Biodex leg fatigue test. Data is presented as change in scale from pre fatigue test to post fatigue test, with a higher score indicating a greater level of fatigue.
Time Frame	after 4 weeks of active drug

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil / Placebo	Tadalafil / Placebo	Placebo / Sildenafil	Placebo / Tadalafil
Arm/Group Description	50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 0-4. Placebo for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 0-4. Placebo for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 50 mg/day Sildenafil: (Other Name: Viagra, Revatio) for weeks 5-8. Sildenafil: 50 mg/day for 4 weeks Placebo: Placebo 1 capsule per day for four weeks.	Placebo for weeks 0-4. 10 mg/day Tadalafil: (Other Name: Cialis, Adcirca) for weeks 5-8. tadalafil: 10 mg/day for 4 weeks. Placebo: Placebo 1 capsule per day for four weeks.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [units on a scale]	4.5 (2.38)	3.5 (1.73)	5.25 (4.27)	6.0 (1.83)

5. Secondary Outcome

Title	Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo
Description	Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of placebo

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	145.86 (97.73)	104.17 (23.66)	149.14 (62.67)	148.34 (47.26)

6. Secondary Outcome

Title	Maximum Peak Isometric Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug.
Description	Peak isometric strength is measured on a Biodex System 4 Pro. This test is isolated to the quadricep muscle of one leg. Isometric test is performed at 90 degrees with 5 seconds of force production for each contraction and 15 seconds of rest. 1 set of 3 contractions at 100% force performed. Isometric strength was measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of active drug

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	140.09 (82.29)	110.39 (21.26)	133.81 (58.04)	139.96 (50.47)

7. Secondary Outcome

Title	Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Placebo.
Description	Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of placebo

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	105.15 (49.46)	78.59 (10.25)	117.71 (39.86)	111.67 (23.43)

8. Secondary Outcome

Title	Maximum Peak Isokinetic Leg Strength as Measured by Biodex Pro4 After 4 Weeks of Active Drug
Description	Isokinetic strength (knee extension) is measured on a Biodex System Pro 4 within a 75 degree range of motion. Subjects performed concentric contractions at a fixed speed of 120 degree/sec. 1 set of 3 contractions were performed at 100% force. Isokinetic strength will be measured at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of active drug

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [Newton-Meters]	106.79 (49.69)	79.33 (11.69)	116.48 (37.83)	114.75 (36.49)

9. Secondary Outcome

Title	Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0.
Description	Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 0

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	5	4	5	4
Mean (Standard Deviation) [kilograms]	44.60 (11.62)	41.43 (4.72)	49.93 (10.63)	54.45 (14.28)

10. Secondary Outcome

Title	Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4.
Description	Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 4

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	5	4
Mean (Standard Deviation) [kilograms]	46.29 (14.40)	41.02 (4.05)	50.61 (10.67)	54.85 (14.71)

11. Secondary Outcome

Title	Lean Body Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8.
Description	Lean Body Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 8

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [kilograms]	46.22 (14.68)	40.76 (4.38)	52.09 (10.03)	55.10 (14.42)

12. Secondary Outcome

Title	Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 0.
Description	Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 0

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	5	4	5	4
Mean (Standard Deviation) [kilograms]	32.35 (11.40)	37.21 (6.81)	32.72 (5.92)	32.10 (6.90)

13. Secondary Outcome

Title	Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 4.
Description	Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 4

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	5	4
Mean (Standard Deviation) [kilograms]	33.16 (12.42)	37.12 (6.35)	32.30 (5.55)	32.47 (7.08)

14. Secondary Outcome

Title	Fat Mass as Measured by Dual Energy X-ray Absorptiometry at Week 8.
Description	Fat Mass is calculated from a whole body scan measured on a dual energy x-ray absorptiometry.
Time Frame	week 8

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [kilograms]	33.60 (12.51)	37.02 (6.21)	32.40 (5.83)	32.79 (7.12)

15. Secondary Outcome

Title	Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Placebo
Description	Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of placebo

Outcome Measure Data

Analysis Population Description

1 subject did not complete the walking test

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	3	4	4	4
Mean (Standard Deviation) [meters]	203.82 (30.51)	189.79 (38.12)	198.41 (14.04)	202.80 (37.84)

16. Secondary Outcome

Title	Walking Distance at 100% Effort as Measured by Walking Test After 4 Weeks of Active Drug
Description	Walking performance will be assessed during 2 minutes of walking in long corridor hallways. Subjects will be asked to walk at 100% effort (as quickly as they can safely walk without running) for 2 minutes. Distance traveled for the 2 minutes will be recorded. The walking test will be completed at week 4 and week 8. Depending on grouping, the week 4 and week 8 measures may be placebo or active drug. Data will be reported as after 4 weeks of placebo or after 4 weeks of active drug.
Time Frame	after 4 weeks of active drug

Outcome Measure Data

Analysis Population Description

1 subject did not complete the walking test.

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	3	4	4	4
Mean (Standard Deviation) [meter]	197.01 (32.72)	178.56 (17.84)	200.19 (13.99)	203.46 (31.11)

17. Secondary Outcome

Title	Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 0
Description	Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.
Time Frame	Week 0

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [scores on a scale]	9.66 (19.55)	-7.5 (5.45)	-8 (3.61)	-3.75 (9.54)

18. Secondary Outcome

Title	Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 4
Description	Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.
Time Frame	week 4

Outcome Measure Data

Analysis Population Description

1 subject did not complete the week 4 MFSI questionnaire

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	3	4	4
Mean (Standard Deviation) [scores on a scale]	6.33 (26.08)	-3.33 (10.97)	-6.33 (2.31)	-3.5 (12.66)

19. Secondary Outcome

Title	Perceptual Fatigue as Measured by Multidimensional Fatigue Symptom Inventory - Short Form Total Score at Week 8
Description	Fatigue symptoms will be measured using the 30-item Multidimensional Fatigue Symptom Inventory - Short Form, a validated measure that yields one overall score of total fatigue calculated using five sub scales (general, physical, emotional, mental, vigor). With the exception of the vigor sub scale, higher scores indicate greater fatigue. Total fatigue score is calculated by summing the sub categories (general, physical, emotional and mental) and subtracting vigor. Total scores range from -24 to 96, with a higher score indicating more fatigue.
Time Frame	week 8

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [scores on a scale]	9.67 (19.09)	3.25 (27.54)	-9.67 (6.81)	-9.25 (1.26)

20. Other Pre-specified Outcome

Title	Hemoglobin Level at Week 0
Description	Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.
Time Frame	week 0

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [g/dL]	13.42 (0.97)	12.78 (0.71)	12.4 (0.53)	13.05 (0.90)

21. Other Pre-specified Outcome

Title	Hemoglobin Level Measured at Week 4
Description	Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.
Time Frame	week 4

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [g/dL]	13.05 (0.49)	12.03 (0.43)	12.6 (0.37)	13.2 (0.47)

22. Other Pre-specified Outcome

Title	Hemoglobin Level Measured at Week 8
Description	Hemoglobin was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 11.6 - 15.0 g/dL.
Time Frame	week 8

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [g/dL]	13.55 (0.35)	11.97 (0.76)	12.5 (0.08)	12.95 (1.17)

23. Other Pre-specified Outcome

Title	Hematocrit Level Measured at Week 0
Description	Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.
Time Frame	week 0

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [percent of red blood cells]	39.53 (2.16)	38.55 (1.42)	37.25 (2.07)	31.88 (13.09)

24. Other Pre-specified Outcome

Title	Hematocrit Level Was Measured at 4 Weeks
Description	Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.
Time Frame	4 weeks

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [percent of red blood cells]	39.08 (0.84)	37.38 (0.82)	38.13 (0.77)	39.1 (1.81)

25. Other Pre-specified Outcome

Title	Hematocrit Level Measured at Week 8
Description	Hematocrit was measured by University of Texas Medical Branch Clinical Laboratory. Normal ranges are 35.7 - 45.2%.
Time Frame	week 8

Outcome Measure Data

Analysis Population Description

[Not Specified]

Arm/Group Title	Sildenafil, Then Placebo	Tadalfil, Then Placebo	Placebo, Then Sildenafil	Placebo, Then Tadalafil
Arm/Group Description	Sildenafil daily (50mg/day) for weeks 0-4. Then Placebo daily for weeks 5-8.	Tadalafil (10mg/day) for week 0-4. Then Placebo daily for week 5-8.	Placebo daily for weeks 0-4. Then Sildenafil daily (50mg/day) for weeks 5-8.	Placebo for week 0-4, then Tadalafil (10mg/day) for week 5-8.
Measure Participants	4	4	4	4
Mean (Standard Deviation) [percent of red blood cells]	40.38 (0.44)	36.6 (1.94)	38.1 (1.19)	38.4 (3.24)

Adverse Events

Arm/Group Title	Sildenafil		Tadalfil		Placebo
Arm/Group Description	Sildenafil (50mg/day) daily for 4 weeks.		Tadalafil (10mg/day) daily for 4 weeks.		Placebo daily for week 4 weeks.
All Cause Mortality
	Sildenafil		Tadalfil		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	0/10 (0%)		0/8 (0%)		0/18 (0%)
Serious Adverse Events
	Sildenafil		Tadalfil		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	0/10 (0%)		0/8 (0%)		0/18 (0%)
Other (Not Including Serious) Adverse Events
	Sildenafil		Tadalfil		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	2/10 (20%)		0/8 (0%)		0/18 (0%)
General disorders
Syncope	1/10 (10%)	1	0/8 (0%)	0	0/18 (0%)	0
Skin and subcutaneous tissue disorders
Redness at site of muscle biopsy	1/10 (10%)	1	0/8 (0%)	0	0/18 (0%)	0

Limitations/Caveats

[Not Specified]

More Information

Certain Agreements

Principal Investigators are NOT employed by the organization sponsoring the study.

There is NOT an agreement between Principal Investigators and the Sponsor (or its agents) that restricts the PI's rights to discuss or publish trial results after the trial is completed.