Metformin Gastric Retention (GR) Formulation
The term "gastric retention" refers to a specific extended-release formulation of metformin that uses proprietary drug delivery technology to retain the tablet in the stomach for prolonged, controlled release of the medication. 1, 2
Formulation Details
Metformin gastric retention (metformin GR), also marketed as Glumetza, is an extended-release formulation developed by DepoMed using patented gastric retention drug delivery technology. 1, 2 This formulation is distinct from standard extended-release metformin products.
Key Characteristics:
- Available in 500 mg and 1000 mg tablet strengths for once-daily dosing 1, 2
- The 500 mg dose was developed using DepoMed's proprietary GR technology 1, 2
- The 1000 mg dose was developed by Biovail using Smartcoat delivery technology 1, 2
- FDA approved in June 2005 for treatment of type 2 diabetes mellitus 1
Mechanism of Gastric Retention
The gastric retention technology is designed to keep the tablet in the stomach longer than conventional formulations, allowing for controlled, sustained release of metformin over an extended period. 3 This approach takes advantage of the fact that metformin is primarily absorbed in the upper gastrointestinal tract. 4
Clinical Advantages:
- Demonstrates positive food effect and should be administered with a meal, preferably the evening meal 3
- Nearly linear dose proportionality with relative bioavailability of 80% (highest to lowest dose), compared to only 58% for immediate-release metformin 3
- Similar bioavailability when administered once daily compared to immediate-release metformin given twice daily 3
Clinical Efficacy and Tolerability
In pivotal phase III trials involving more than 1000 patients with type 2 diabetes, metformin GR significantly decreased glycosylated hemoglobin levels similarly to immediate-release metformin across three different dosing regimens. 1, 2
- Well tolerated with an excellent safety profile regarding gastrointestinal adverse events 1, 2
- Maintained glycemic control for 24 weeks in controlled trials and an additional 24 weeks in open-label extension studies 3
Important Distinction
This gastric retention formulation should not be confused with standard extended-release metformin (such as Glucophage XR marketed by Bristol-Myers Squibb), which uses different extended-release technology. 5 The standard extended-release formulation mentioned in diabetes guidelines is typically dosed once daily but does not specifically utilize gastric retention technology. 5