Prescription Drug Information: Metformin Hydrochloride (Page 4 of 6)

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term carcinogenicity studies have been performed in rats (dosing duration of 104 weeks) and mice (dosing duration of 91 weeks) at doses up to and including 900 mg/kg/day and 1,500 mg/kg/day, respectively. These doses are both approximately 3 times the maximum recommended human daily dose of 2,550 mg based on body surface area comparisons. No evidence of carcinogenicity with metformin was found in either male or female mice. Similarly, there was no tumorigenic potential observed with metformin in male rats. There was, however, an increased incidence of benign stromal uterine polyps in female rats treated with 900 mg/kg/day.

There was no evidence of a mutagenic potential of metformin in the following in vitro tests: Ames test ( S. typhimurium), gene mutation test (mouse lymphoma cells), or chromosomal aberrations test (human lymphocytes). Results in the in vivo mouse micronucleus test were also negative.

Fertility of male or female rats was unaffected by metformin when administered at doses as high as 600 mg/kg/day, which is approximately 2 times the maximum recommended human daily dose of 2,550 mg based on body surface area comparisons.

14 CLINICAL STUDIES

14.2 Metformin Hydrochloride Extended-Release Tablets

A 24-week, double-blind, placebo-controlled study of metformin hydrochloride extended-release tablets, taken once daily with the evening meal, was conducted in patients with type 2 diabetes mellitus who had failed to achieve glycemic control with diet and exercise. Patients entering the study had a mean baseline HbA 1c of 8.0% and a mean baseline FPG of 176 mg/dL. The treatment dose was increased to 1,500 mg once daily if at Week 12 HbA 1c was ≥ 7.0% but < 8.0% (patients with HbA 1c ≥ 8.0% were discontinued from the study). At the final visit (24-week), mean HbA 1c had increased 0.2% from baseline in placebo patients and decreased 0.6% with metformin hydrochloride extended-release tablets.

A 16-week, double-blind, placebo-controlled, dose-response study of metformin hydrochloride extended-release tablets, taken once daily with the evening meal or twice daily with meals, was conducted in patients with type 2 diabetes mellitus who had failed to achieve glycemic control with diet and exercise. The results are shown in Table 6.

Table 6: Mean Changes from Baseline in HbA 1c and Fasting Plasma Glucose at Week 16 Comparing Metformin Hydrochloride Extended-Release Tablets vs Placebo in Patients with Type 2 Diabetes Mellitus
Metformin Hydrochloride Extended-Release Tablets Placebo
500 mg Once Daily 1,000 mg Once Daily 1,500 mg Once Daily 2,000 mg Once Daily 1,000 mg Twice Daily
*
All comparisons versus Placebo
Hemoglobin A 1c (%) (n = 115) (n = 115) (n = 111) (n = 125) (n = 112) (n = 111)
Baseline 8.2 8.4 8.3 8.4 8.4 8.4
Change at FINAL VISIT –0.4 –0.6 –0.9 –0.8 –1.1 0.1
p-value * < 0.001 < 0.001 < 0.001 < 0.001 < 0.001
FPG (mg/dL) (n = 126) (n = 118) (n = 120) (n = 132) (n = 122) (n = 113)
Baseline 182.7 183.7 178.9 181.0 181.6 179.6
Change at FINAL VISIT –15.2 –19.3 –28.5 –29.9 –33.6 7.6
p-value * < 0.001 < 0.001 < 0.001 < 0.001 < 0.001

Mean baseline body weight was 193 lbs, 192 lbs, 188 lbs, 196 lbs, 193 lbs and 194 lbs in the metformin hydrochloride extended-release tablets 500 mg, 1,000 mg, 1,500 mg, and 2,000 mg once daily, 1,000 mg twice daily and placebo arms, respectively. Mean change in body weight from baseline to week 16 was -1.3 lbs, -1.3 lbs, -0.7 lbs, -1.5 lbs, -2.2 lbs and -1.8 lbs, respectively.

A 24-week, double-blind, randomized study of metformin hydrochloride extended-release tablets, taken once daily with the evening meal, and metformin hydrochloride tablets, taken twice daily (with breakfast and evening meal), was conducted in patients with type 2 diabetes mellitus who had been treated with metformin hydrochloride tablets 500 mg twice daily for at least 8 weeks prior to study entry. The results are shown in Table 7.

Table 7: Mean Changes from Baseline in HbA 1c and Fasting Plasma Glucose at Week 24 Comparing Metformin Hydrochloride Extended-Release Tablets vs Metformin Hydrochloride Tablets in Patients with Type 2 Diabetes Mellitus
Metformin Hydrochloride Tablets 500 mg Twice Daily Metformin Hydrochloride Extended-Release Tablets
1,000 mg Once Daily 1,500 mg Once Daily
*
n = 68
Hemoglobin A 1c (%) (n = 67) (n = 72) (n = 66)
Baseline 7.06 6.99 7.02
Change at FINAL VISIT 0.14 * 0.27 0.13
(95% CI) (–0.04, 0.31) (0.11, 0.43) (–0.02, 0.28)
FPG (mg/dL) (n = 69) (n = 72) (n = 70)
Baseline 127.2 131.0 131.4
Change at FINAL VISIT 14.0 11.5 7.6
(95% CI) (7.0, 21.0) (4.4, 18.6) (1.0, 14.2)

Mean baseline body weight was 210 lbs, 203 lbs and 193 lbs in the metformin hydrochloride tablets 500 mg twice daily, and metformin hydrochloride extended-release tablets 1,000 mg and 1,500 mg once daily arms, respectively. Mean change in body weight from baseline to week 24 was 0.9 lbs, 1.1 lbs and 0.9 lbs, respectively.

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