MEP: Effects of Metformin During Nicotine Withdrawal

• Sponsor: University of Pennsylvania (Other)
• Overall Status: Completed
• CT.gov ID: NCT03593538
• Collaborator: Pennsylvania Department of Health (Other)
• Enrollment: 80
• Location: 1
• Arms: 3
• Actual Duration (Months): 47.4
• Patients Per Site Per Month: 1.7

Study Details

Study Description

Brief Summary

The purpose of this study is to test the effects of a medication called metformin (Glucophage®) on smoking behavior. This medication is FDA-approved for treatment of type-2 diabetes. It is being used for research purposes in this study. Participants will be randomized to one of 3 treatment groups: low dose of metformin, high dose of metformin, or placebo.

Condition or Disease	Intervention/Treatment	Phase
Smoking; HIV-1-infection	Drug: Metformin; Drug: Placebo	Phase 2

Detailed Description

There is a need for novel approaches to optimize smoking cessation treatment to help more smokers quit. Mood disturbance and cognitive deficits during nicotine withdrawal may be important treatment targets given their association with smoking relapse. In addition, factors such as HIV-1 infection may exacerbate abstinence effects on mood and cognitive deficits and thus should be measured and controlled for. The investigators hypothesize that the FDA-approved medication, metformin, will attenuate withdrawal-related mood disturbance and cognitive deficits, controlling for HIV status. Using a well-validated abstinence challenge paradigm, the investigators propose a placebo-controlled double-blind parallel arm study with one between-subjects factor of medication (low dose: 500 mg, high dose: 1500 mg, and placebo). Non-treatment seeking smokers (HIV-: n=54; 18 per group) will complete this 23 day study.

Study Design

• Study Type: Interventional
• Actual Enrollment: 80 participants
• Allocation: Randomized
• Intervention Model: Parallel Assignment
• Masking: Double (Participant, Investigator)
• Primary Purpose: Treatment
• Official Title: Effects of Metformin on Mood and Cognition During Nicotine Withdrawal
• Actual Study Start Date: Apr 1, 2016
• Actual Primary Completion Date: Mar 13, 2020
• Actual Study Completion Date: Mar 13, 2020

Arms and Interventions

Arm	Intervention/Treatment
Experimental: Low Dose Metformin Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day	Drug: Metformin; Metformin capsule; Other Names: Glucophage ; Drug: Placebo; Sucrose filler in gel capsules; Other Names: Placebo (for Metformin)
Experimental: High Dose Metformin Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day	Drug: Metformin; Metformin capsule; Other Names: Glucophage
Placebo Comparator: Placebo Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day	Drug: Placebo; Sucrose filler in gel capsules; Other Names: Placebo (for Metformin)

Outcome Measures

Primary Outcome Measures

1. Mood Following 24h of Smoking Abstinence [Day 23]

   Self-reported mood on the Positive and Negative Affect Schedule (PANAS), a 20-item Likert-format measure that assesses Positive Affect (PA; 10 items, e.g., enthusiastic, strong) and Negative Affect (NA; 10 items, e.g., distressed, upset). The minimum value for each subscale is 10 and the maximum value is 50. Higher scores indicate greater positive or negative affect.

2. Cognitive Function Following 24h of Smoking Abstinence [Day 23]

   Composite score of computer-based neurocognitive tasks (N-back Working Memory Task, Stop Signal Task, Hopkins Verbal Learning Test - Revised [HVLT-R]) designed to test working memory and attention. A standardized z-score (mean=0, standard deviation=1) was calculated for the primary outcome for each task and an average was computed from the three z-scores. Higher scores indicated better cognitive performance.

Secondary Outcome Measures

1. Self-reported Smoking Behavior [Days 7, 14, 21, and 23]

   Cigarettes smoked per day as reported on the Timeline Follow-Back (TLFB). Cigarettes smoked per day is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which uses a 24-hr time reference.

2. Self-reported Withdrawal Symptoms [Days 7, 14, 21, and 23]

   The "Minnesota Nicotine Withdrawal Scale - Revised version"(MNWS_R) captures the current state of nicotine withdrawal. The scale assesses eight DSM-IV items of nicotine withdrawal including: dysphoria or depressed mood, insomnia, irritability/frustration/anger, anxiety, decreased heart rate, difficulty concentrating, restlessness, and increased appetite/weight gain. Participants rate the intensity of their symptoms on the following scale: 0 = none, 1 = slight, 2 = mild, 3 = moderate, 4 = severe and a summary score will be calculated. Withdrawal is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which uses a 24-hr time reference. The scale ranges from 0 to 32 with higher scores indicating more severe withdrawal symptoms.

3. Self-reported Craving for Cigarettes [Days 7, 14, 21, and 23]

   The 10-item brief Questionnaire of Smoking Urges (QSU-B) assesses craving for cigarettes. The QSU-B contains 2 sub-scales (anticipation of reward, relief from negative affect) which are summed to create the total score. Similar to withdrawal symptoms, craving is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which will use a 24-hr time reference. Items are rated from 1 (strongly disagree) to 7 (strongly agree) and are summed to create a total score ranging from 10 to 70. Higher scores indicate higher levels of craving.

4. Subjective Effects of Smoking [Days 7, 14, 21, and 23]

   The Cigarette Evaluation Scale (CES), developed to assess subjective effects of smoking, is an 11-item Likert-format measure. Questions include items for nausea and dizziness, craving relief, and enjoyment of airway sensations and comprise 3 scales: satisfaction score, psychological relief score, and toxicity score. Each scale is the average of items with a minimum value of 1 and a maximum value of 7. Higher scores indicate more satisfaction, greater psychological relief, and higher subjective toxicity, respectively.

5. Subjective Sensory Experience of Smoking [Days 7, 14, 21, and 23]

   The Rose Sensory Questionnaire (SQ), a 9-item Likert-format measure, assesses how much participants liked the cigarette smoked (liking scale) and how high in nicotine the cigarettes appeared to be (strength scale). The questionnaire also includes a diagram of the respiratory tract and asks participants to rate the strength of the cigarette puffs on their tongue, nose, back of mouth and throat, windpipe, and chest. Each scale is the average of items with a minimum value of 1 and a maximum value of 7. Higher scores indicate greater liking and perceived strength, respectively.

Eligibility Criteria

Criteria

• Ages Eligible for Study: 18 Years to 65 Years
• Sexes Eligible for Study: All
• Accepts Healthy Volunteers: Yes

Inclusion Criteria

Eligible subjects will be males and females:

1. 18 years of age or older who self-report smoking at least 5 cigarettes (menthol and non-menthol) per day, on average for the past 6 months.

2. HIV status

3. HIV-infected smokers: diagnosed with HIV infection and exhibiting viral load of less than or equal to 1000 copies/mL and CD4+ counts of greater than or equal to 200 cells/mm3 within 6 months prior to enrollment.

4. HIV-uninfected smokers: no diagnosis of HIV, either via blood test or self-report.

5. Must not currently be interested in quitting smoking.

6. Women of childbearing potential (based on medical history) must consent to use a medically accepted method of birth control (e.g., condoms and spermicide, oral contraceptive, Depo-Provera injection, contraceptive patch, tubal ligation) or abstain from sexual intercourse during the time they are in the study and using transdermal nicotine.

7. If current or past diagnosis of bipolar disorder, eligible if:

8. No psychotic features

9. MADRS: total score less than 8 (past 4 weeks), suicidal item score less than1 (past 4 weeks)

10. Y-MRS: total score less than 8 (past 4 weeks), irritability, speech content, disruptive or aggressive behavior items score less than 3 (past 4 weeks)

11. No psychiatric hospitalization or Emergency Room visits for psychiatric issues in the past 6 months

12. No aggressive or violent acts or behavior in the past 6 months

13. Able to communicate fluently in English.

14. Capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the combined consent/HIPAA form.

Exclusion Criteria

Smoking Behavior:

1. Current enrollment in a smoking cessation program, or use of other smoking cessation medications in the last month or plans to do either in the next 2 months.

2. Daily use of chewing tobacco, snuff and/or snus, or electronic cigarettes.

Alcohol/Drugs:

1. Self-report current alcohol consumption that exceeds 25 standard drinks/week over the past 6 months. Subjects will be told to limit or avoid the use of alcohol while in the study to avoid any adverse reactions to the study medication.

2. Current untreated and unstable diagnosis of substance dependence (eligible if past use and if receiving treatment and stable for at least 30 days). Current untreated and unstable diagnosis of substance abuse requires Study Physician approval.

3. A positive urine drug screen for cocaine, amphetamines, methamphetamines, PCP, barbiturates and ecstasy (MDMA)at Intake, or any testing session (see Measures and Table 1 for details). Participants believed to have a false-positive result may continue in the study, with investigator approval.

Medical:

1. Females who self-report current pregnancy, planning a pregnancy during the study, or currently breastfeeding/lactating. All female subjects of child-bearing potential shall undergo a urine pregnancy test at the Intake, Baseline, PQ-Testing and 24-H Testing sessions.

2. Current diagnosis of unstable and untreated major depression, as determined by self-report & MINI (eligible if stable for at least 30 days).

3. Current or past diagnosis of psychotic disorder, as determined by self-report or MINI.

4. Suicide risk as indicated by at least one of the following on the MINI/CSSRS (the PI &/or PM [LCSW] will be consulted to assess safety and determine eligibility in cases close to the eligibility cutoffs):

5. Current suicidal ideation (within 30 days of enrollment)

6. Two or more lifetime suicide attempts or episodes of suicidal behavior

7. Any suicide attempt or suicidal behavior within 2 years of enrollment

8. Self-reported kidney and/or liver disease or transplant untreated/unstable or within the past 6 months.

9. Heart/Cardiovascular disease (e.g., angina, coronary heart disease, stroke, etc.) in the past 6 months.

10. Type-1 or type-2 diabetes.

11. Uncontrolled hypertension (BP systolic greater than 159 and/or diastolic greater than 99)*.

12. Liver function tests more than 20% outside of the normal range; Gamma-glutamyl Transpepsidase (GGT) values more than 20% outside of the normal range. If Albumin/Globulin ratios are 20% outside of normal range the abnormal value will be evaluated for clinical significance by the Study Physician and eligibility will determined on a case-by-case basis.

13. Renal disease or renal dysfunction (e.g., serum creatinine levels ≥1.5 mg/dL [males], ≥1.4 mg/dL [females]).

14. A blood glucose level less than 70 mg/dl at any visit.

• Participants presenting with SBP greater than 159 mmHg and/or DBP greater than 99 mmHg at the Intake visit will be instructed to sit quietly for 10 minutes. Then the participant will have a second blood pressure reading taken after a 10 minute period. If, after the second reading the SBP greater than 159 mmHg and the DBP greater than 99 mmHg, the individual will be ineligible to participate, unless determined otherwise by the Study PI or Study Physician, upon review.

Medication:

1. Current use or recent discontinuation (within the past 14 days) of any of the following medications:

2. Anti-anxiety or panic disorder medications (e.g., clonazepam, alprazolam).

3. Anti-psychotic medications as assessed on a case-by-case basis

4. Glucophage/metformin

5. Glyburide

6. Furosemide or digoxin

7. Nifedipine

8. Cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, or vancomycin)

9. Participants who report taking prescription opiate-containing medications (Duragesic/fentanyl patches, Percocet, Oxycontin) will require physician approval prior to confirming final eligibility.

10. Current use of any smoking cessation medications (e.g., Chantix/varenicline, Zyban/bupropion, nicotine replacement therapy/gum/patch).

11. For safety reasons, HIV-infected smokers taking dolutegravir (Tivicay) or drugs that contain dolutegravir (e.g., Triumeq) should not take more than 1000 mg of metformin per day. Therefore, individuals taking dolutegravir will be force randomized to either the placebo condition or the low dose condition.

Subjects will be instructed to refrain from using any study prohibited drugs/medications (both recreational and prescription) throughout their participation in the study. After final eligibility is confirmed, subjects who report taking contraindicated medication(s) over the course of the study period may only remain eligible if the Study Physician and/or Principal Investigator determines that the contraindicated medication(s) do/did not impact the study design, data quality, and/or subject safety/welfare. Subjects are permitted to take necessary prescription medications not included within the exclusion list during the study.

General Exclusion:

1. Current, anticipated, or pending enrollment in another research program over the next 2-3 months that could potentially affect subject safety and/or the study data/design as determined by the Principal Investigator and/or Study Physician.

2. Not planning to live in the area for the next two months.

3. Color blindness.

4. Any impairment (physical and/or neurological) including visual or other impairment preventing cognitive task performance.

5. Known allergy to study medication.

6. Planned radiologic studies involving the use of intravascular iodinated contrast materials (e.g., intravenous urogram, intravenous cholangiography, angiography, and computed tomography (CT) scans with intravascular contrast materials) during the course of study participation.

7. Inability to provide informed consent or complete any of the study tasks as determined by the Principal Investigator.

8. Not able to effectively communicate in English (reading, writing, speaking).

9. Missing 3 or more doses during the medication period determined by self-report.

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	Center for Interdisciplinary Research on Nicotine Addiction, University of Pennsylvania	Philadelphia	Pennsylvania	United States	19104

Sponsors and Collaborators

• University of Pennsylvania
• Pennsylvania Department of Health

Investigators

• Principal Investigator: Robert Schnoll, PhD, University of Pennsylvania

Study Documents (Full-Text)

• Study Protocol and Statistical Analysis Plan - Aug 17, 2020
• Informed Consent Form - Nov 9, 2020

More Information

Publications

None provided.

• Responsible Party: Robert Schnoll, Associate Professor, Department of Psychiatry, University of Pennsylvania
• ClinicalTrials.gov Identifier: NCT03593538
• Other Study ID Numbers: 824504
• First Posted: Jul 20, 2018
• Last Update Posted: Mar 26, 2021
• Last Verified: Mar 1, 2021

• Studies a U.S. FDA-regulated Drug Product: Yes
• Studies a U.S. FDA-regulated Device Product: No
• Product Manufactured in and Exported from the U.S.: No
• Additional relevant MeSH terms: Metformin

Study Results

Participant Flow

Pre-assignment Detail	Of the 80 subjects, who signed consent and were deemed eligible to participate, 11 did not attend the Baseline session during which they would begin treatment leaving 69 subjects who started study medication.

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Period Title: Overall Study
STARTED	26	21	22
COMPLETED	15	15	11
NOT COMPLETED	11	6	11

Baseline Characteristics

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo	Total
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules	Total of all reporting groups
Overall Participants	26	21	22	69
Age (years) [Mean (Full Range) ]
Mean (Full Range) [years]	49.8	43.1	50.5	47.9
Sex: Female, Male (Count of Participants)
Female	8 30.8%	6 28.6%	7 31.8%	21 30.4%
Male	18 69.2%	15 71.4%	15 68.2%	48 69.6%
Ethnicity (NIH/OMB) (Count of Participants)
Hispanic or Latino	2 7.7%	2 9.5%	0 0%	4 5.8%
Not Hispanic or Latino	24 92.3%	18 85.7%	22 100%	64 92.8%
Unknown or Not Reported	0 0%	1 4.8%	0 0%	1 1.4%
Race (NIH/OMB) (Count of Participants)
American Indian or Alaska Native	0 0%	1 4.8%	0 0%	1 1.4%
Asian	0 0%	0 0%	0 0%	0 0%
Native Hawaiian or Other Pacific Islander	0 0%	0 0%	0 0%	0 0%
Black or African American	18 69.2%	17 81%	17 77.3%	52 75.4%
White	6 23.1%	2 9.5%	5 22.7%	13 18.8%
More than one race	1 3.8%	0 0%	0 0%	1 1.4%
Unknown or Not Reported	1 3.8%	1 4.8%	0 0%	2 2.9%
Region of Enrollment (Count of Participants)
United States	26 100%	21 100%	22 100%	69 100%
Cigarettes per day (cigarettes per day) [Mean (Full Range) ]
Mean (Full Range) [cigarettes per day]	12.6	12.6	16	13.7

Outcome Measures

1. Primary Outcome

Title	Mood Following 24h of Smoking Abstinence
Description	Self-reported mood on the Positive and Negative Affect Schedule (PANAS), a 20-item Likert-format measure that assesses Positive Affect (PA; 10 items, e.g., enthusiastic, strong) and Negative Affect (NA; 10 items, e.g., distressed, upset). The minimum value for each subscale is 10 and the maximum value is 50. Higher scores indicate greater positive or negative affect.
Time Frame	Day 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Positive Affect	36.5 (2.5)	33.8 (2.8)	37.9 (2.6)
Negative Affect	14.3 (1.3)	13.1 (0.9)	13.9 (1.8)

2. Primary Outcome

Title	Cognitive Function Following 24h of Smoking Abstinence
Description	Composite score of computer-based neurocognitive tasks (N-back Working Memory Task, Stop Signal Task, Hopkins Verbal Learning Test - Revised [HVLT-R]) designed to test working memory and attention. A standardized z-score (mean=0, standard deviation=1) was calculated for the primary outcome for each task and an average was computed from the three z-scores. Higher scores indicated better cognitive performance.
Time Frame	Day 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Mean (Standard Error) [z-score]	-0.018 (0.17)	0.159 (0.22)	-0.204 (0.29)

3. Secondary Outcome

Title	Self-reported Smoking Behavior
Description	Cigarettes smoked per day as reported on the Timeline Follow-Back (TLFB). Cigarettes smoked per day is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which uses a 24-hr time reference.
Time Frame	Days 7, 14, 21, and 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Day 7	13.9 (2.2)	8 (1.1)	11.2 (1.8)
Day 14	11.8 (1.8)	8.1 (1.0)	10.4 (1.8)
Day 21	12.5 (1.7)	7.4 (0.9)	10.1 (1.2)
Day 23	0 (0)	0 (0)	0 (0)

4. Secondary Outcome

Title	Self-reported Withdrawal Symptoms
Description	The "Minnesota Nicotine Withdrawal Scale - Revised version"(MNWS_R) captures the current state of nicotine withdrawal. The scale assesses eight DSM-IV items of nicotine withdrawal including: dysphoria or depressed mood, insomnia, irritability/frustration/anger, anxiety, decreased heart rate, difficulty concentrating, restlessness, and increased appetite/weight gain. Participants rate the intensity of their symptoms on the following scale: 0 = none, 1 = slight, 2 = mild, 3 = moderate, 4 = severe and a summary score will be calculated. Withdrawal is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which uses a 24-hr time reference. The scale ranges from 0 to 32 with higher scores indicating more severe withdrawal symptoms.
Time Frame	Days 7, 14, 21, and 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Day 7	7.4 (1.3)	6.3 (0.9)	7.9 (1.5)
Day 14	7.0 (1.4)	6.2 (0.8)	8.3 (2.2)
Day 21	7.8 (1.6)	5.5 (0.9)	7.1 (1.7)
Day 23	10.5 (2.1)	8.7 (1.3)	11.8 (2.8)

5. Secondary Outcome

Title	Self-reported Craving for Cigarettes
Description	The 10-item brief Questionnaire of Smoking Urges (QSU-B) assesses craving for cigarettes. The QSU-B contains 2 sub-scales (anticipation of reward, relief from negative affect) which are summed to create the total score. Similar to withdrawal symptoms, craving is assessed using a "past week" time reference for all time points except the 24-hr testing visit on Day 23, which will use a 24-hr time reference. Items are rated from 1 (strongly disagree) to 7 (strongly agree) and are summed to create a total score ranging from 10 to 70. Higher scores indicate higher levels of craving.
Time Frame	Days 7, 14, 21, and 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Day 7	32.9 (4.4)	26.1 (4.2)	40.3 (5.8)
Day 14	31.2 (3.6)	22.3 (3.8)	38.4 (5.9)
Day 21	28.3 (3.8)	21.4 (3.3)	36.7 (5.2)
Day 23	45.2 (5.0)	39.9 (4.4)	52.9 (3.8)

6. Secondary Outcome

Title	Subjective Effects of Smoking
Description	The Cigarette Evaluation Scale (CES), developed to assess subjective effects of smoking, is an 11-item Likert-format measure. Questions include items for nausea and dizziness, craving relief, and enjoyment of airway sensations and comprise 3 scales: satisfaction score, psychological relief score, and toxicity score. Each scale is the average of items with a minimum value of 1 and a maximum value of 7. Higher scores indicate more satisfaction, greater psychological relief, and higher subjective toxicity, respectively.
Time Frame	Days 7, 14, 21, and 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Satisfaction (Day 7)	4.7 (0.4)	3.8 (0.4)	5.8 (0.4)
Satisfaction (Day 14)	5.0 (0.4)	3.4 (0.5)	5.2 (0.4)
Satisfaction (Day 21)	4.5 (0.4)	3.6 (0.4)	5.0 (0.4)
Satisfaction (Day 23)	5.1 (0.5)	3.6 (0.6)	4.9 (0.6)
Psychological Relief (Day 7)	2.7 (0.4)	2.0 (0.2)	4.0 (0.6)
Psychological Relief (Day 14)	3.0 (0.5)	2.0 (0.3)	3.5 (0.5)
Psychological Relief (Day 21)	2.8 (0.5)	1.9 (0.3)	3.9 (0.6)
Psychological Relief (Day 23)	3.2 (0.4)	2.1 (0.3)	3.6 (0.5)
Toxicity (Day 7)	1.1 (0.06)	1.4 (0.18)	1.3 (0.15)
Toxicity (Day 14)	1.1 (.08)	1.6 (0.30)	1.3 (.15)
Toxicity (Day 21)	1.3 (0.11)	1.2 (0.11)	1.3 (0.16)
Toxicity (Day 23)	2.1 (0.26)	2.1 (0.26)	2.6 (0.45)

7. Secondary Outcome

Title	Subjective Sensory Experience of Smoking
Description	The Rose Sensory Questionnaire (SQ), a 9-item Likert-format measure, assesses how much participants liked the cigarette smoked (liking scale) and how high in nicotine the cigarettes appeared to be (strength scale). The questionnaire also includes a diagram of the respiratory tract and asks participants to rate the strength of the cigarette puffs on their tongue, nose, back of mouth and throat, windpipe, and chest. Each scale is the average of items with a minimum value of 1 and a maximum value of 7. Higher scores indicate greater liking and perceived strength, respectively.
Time Frame	Days 7, 14, 21, and 23

Outcome Measure Data

Analysis Population Description

Study Completers

Arm/Group Title	Low Dose Metformin	High Dose Metformin	Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule	Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
Measure Participants	15	15	11
Liking scale (Day 7)	4.6 (0.33)	3.8 (0.36)	5.0 (0.33)
Liking scale (Day 14)	4.6 (0.29)	3.6 (0.44)	4.8 (0.43)
Liking scale (Day 21)	4.4 (0.37)	3.6 (0.43)	4.7 (0.29)
Liking scale (Day 23)	4.7 (0.36)	3.7 (0.43)	4.8 (0.48)
Strength scale (Day 7)	3.9 (0.34)	3.4 (0.45)	3.9 (0.42)
Strength scale (Day 14)	4.0 (0.39)	2.9 (0.47)	3.9 (0.39)
Strength scale (Day 21)	3.5 (0.43)	2.9 (0.44)	3.5 (0.29)
Strength scale (Day 23)	4.1 (0.40)	3.4 (0.51)	4.0 (0.47)

Adverse Events

Time Frame	Through study completion, an average of 30 days
Arm/Group Title	Low Dose Metformin		High Dose Metformin		Placebo
Arm/Group Description	Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 500 mg and 1 Placebo capsule per day; Days 15-23: Metformin 500 mg and 2 Placebo capsules per day Metformin: Metformin capsule Placebo: Sucrose filler in gel capsules		Days 1-7: Metformin 500 mg per day; Days 8-14: Metformin 1000 mg per day; Days 15-23: Metformin 1500 mg per day Metformin: Metformin capsule		Days 1-7: 1 Placebo capsule per day; Days 8-14: 2 Placebo capsules per day; Days 15-23: 3 Placebo capsules per day Placebo: Sucrose filler in gel capsules
All Cause Mortality
	Low Dose Metformin		High Dose Metformin		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	0/26 (0%)		0/21 (0%)		0/22 (0%)
Serious Adverse Events
	Low Dose Metformin		High Dose Metformin		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	0/26 (0%)		0/21 (0%)		0/22 (0%)
Other (Not Including Serious) Adverse Events
	Low Dose Metformin		High Dose Metformin		Placebo
	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events	Affected / at Risk (%)	# Events
Total	12/26 (46.2%)		11/21 (52.4%)		14/22 (63.6%)
Gastrointestinal disorders
Constipation	0/26 (0%)		1/21 (4.8%)		1/22 (4.5%)
Diarrhea	1/26 (3.8%)		0/21 (0%)		1/22 (4.5%)
Heartburn	0/26 (0%)		0/21 (0%)		1/22 (4.5%)
Nausea	1/26 (3.8%)		1/21 (4.8%)		0/22 (0%)
General disorders
Headache	1/26 (3.8%)		1/21 (4.8%)		3/22 (13.6%)
Increased Sweating	1/26 (3.8%)		1/21 (4.8%)		1/22 (4.5%)
Minor Head Injury	1/26 (3.8%)		0/21 (0%)		0/22 (0%)
Mouth Sores	0/26 (0%)		0/21 (0%)		1/22 (4.5%)
Respiratory, thoracic and mediastinal disorders
Bronchitis	1/26 (3.8%)		0/21 (0%)		0/22 (0%)
Upper Respiratory Infection	0/26 (0%)		0/21 (0%)		1/22 (4.5%)
Vascular disorders
Hypertension	6/26 (23.1%)		7/21 (33.3%)		5/22 (22.7%)

Limitations/Caveats

[Not Specified]

More Information

Certain Agreements

All Principal Investigators ARE 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.