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Table 1 Study Characteristics

From: Metformin in prevention and treatment of antipsychotic induced weight gain: a systematic review and meta-analysis

  Study Methods Participants Country Numbers Intervention
1. Armen 2008 Parallel group RCT
Duration 12 weeks
Age < 20 years
On risperidone 2–6 mg
Saudi Arabia Metformin N = 16
Placebo N = 16
Metformin 500 mg twice daily or placebo
2. Baptista 2006 Parallel group RCT
Duration 14 weeks
Age ≥18 years
Olanzapine monotherapy > 4 months
Venezuela Metformin N = 19
Placebo N = 18
Metformin 850–1750 mg
Balanced diet of 2500-300Kcal
3. Baptista 2007 Parallel group RCT
Duration 12 weeks
Age ≥18 years
Olanzapine monotherapy > 4 months
Venezuela Metformin N = 36
Placebo N = 36
Metformin 850–2550 mg or placebo
Diet and exercise counseling at start of study
4. Carrizo 2009 Parallel group RCT
Duration 14 weeks
clozapine treatment > 3 months Venezuela Metformin N = 31
Placebo N = 30
Extended release metformin 500–1000 mg/day or placebo
5. Chen Parallel group RCT
Duration 24 weeks
clozapine treatment > 3 months
BMI ≥24 or one metabolic syndrome criteria
Taiwan Metformin N = 28
Placebo N = 27
Metformin 1500 mg/day
6. De Silva 2015 Parallel group RCT
Duration 24 weeks
Age ≥18 years
Weight gain > 10 % of body weight
Females 78.8 %
Sri Lanka Metformin N = 34
Placebo N = 32
Metformin or placebo 500 mg twice daily
Diet and exercise counseling given at start of study
7. Jarskog 2013 Parallel group RCT
Duration 16 weeks
Age 18–65 years
BMI ≥27
Duration of illness ≥ 1 year
Females 30.8 %
United States Metformin
N = 75
Placebo N = 71
Metformin 500 mg twice daily increased upto maximum of 2000 mg/day or placebo
Weekly diet and exercise counseling
8. Klein Parallel group RCT
Duration 16 weeks
Age 10–17 years
Gained > 10 % body weight
United States Metformin N = 34
Placebo N = 32
Metformin 850 mg twice daily or placebo
nutritional counseling
9. Wang 2012 Parallel group RCT
Duration 12 weeks
Age 18–60 years
Gained > 7 % of body weight
China Metformin N = 32
Placebo N = 34
Metformin 500 mg twice daily or placebo
10. Wu 2012 Parallel group RCT
Duration 24 weeks
Age 18–40 years
First episode Female patients only
China Metformin N = 42
Placebo N = 42
Metformin 1000 mg/day or placebo
11. Wu 2008a JAMA Parallel group RCT
Duration 12 weeks
Age 18–45 years
First episode patient who gained > 10 % of bodyweight
China Metformin N = 32
Placebo N = 32
Metformin 750 mg or placebo
(also metformin + lifestyle and lifestyle + placebo groups)
12. Wu 2008b AM J Parallel group RCT
Duration 12 weeks
Age 18–50 years
First episode patients on olanzapine
China Metformin N = 18
Placebo N = 19
Metformin 250 mg thrice daily or placebo
No special diet or exercise program