TABLE 2.
Dose Schedules, Advantages, and Disadvantages of Different Metformin Formulations
| Metformin Formulation | Year of FDA Approval (10,33–36) | Starting Dose (27,29,31,32) | Generic Dose (If Available) | Approximate Cost ($/Month) | Advantages | Disadvantages |
|---|---|---|---|---|---|---|
| IR tablets | ● Low cost | ● Large tablet size or rough texture makes swallowing difficult | ||||
| Glucophage 500, 850, or 1,000 mg | 1995 | 500 mg orally twice daily or 850 mg once daily with meala | 500, 850, or 1,000 mg | 7 (generic) | ● Available in combination with other oral antidiabetic drugs | ● May cause gastrointestinal side effects (especially in early titration phase) |
| ER tablets | ● Low cost of generic metformin ER (similar to IR) | ● Large tablet size | ||||
| Glucophage XR 500 or 750 mg (32) | 2000 | ● 500 mg once daily with the evening mealb | 500 or 750 mg | 10 (generic) | ● Fewer gastrointestinal side effects (improved tolerability) | ● Tablets cannot be broken or crushed |
| Glumetza 500 or 1,000 mg (31) | 2005 | 500 mg once daily with the evening mealc | 500 or 1,000 mg | 750 | ● Available as combination formulations with other oral antidiabetic drugs | ● Higher cost of Glumetza and generic Fortamet compared with generic IR metformin (∼100 and ∼35 times the cost, respectively) |
| Fortamet 500 mg or 1 g (29) | 2004 | ● 500 mg once daily with a full glass of water and the evening meald | 250 (generic) | |||
| Liquid | ● Easy to administer | ● Prescribing physicians have relatively limited experience with the formulation | ||||
| Riomet 500 mg/5 mL (27) | 2003 | Once daily or twice daily with mealse | 555f | ● Can be taken by patients with physical (dysphagia) or psychological swallowing problems |
Adult dose; increase the dose in increments of 500 mg weekly or 850 mg every 2 weeks up to a maximum dose of 2,550 mg per day, given in divided doses.
Adult dose; increase the dose in increments of 500 mg weekly up to a maximum of 2,000 mg once daily with the evening meal.
Increase the dose in 500-mg increments every 1–2 weeks if a higher dose is needed and there are no gastrointestinal adverse reactions up to a maximum of 2,000 mg daily.
Gradual dose escalation if needed, not to exceed 2,500 mg daily.
Dosing must be individualized on the basis of both effectiveness and tolerance, while not exceeding the maximum recommended daily dose. The maximum recommended daily dose of Riomet is 2,550 mg (25.5 mL) in adults and 2,000 mg (20 mL) in pediatric patients (aged 10–16 years of age).
Estimated based on an 8.5 mL twice-daily dose.