The FDA has required labeling changes that replace serum creatinine (SCr) with estimated glomerular filtration rate (e GFR) as the parameter used to determine the appropriateness of treatment with the biguanide metformin (, and others) in patients with renal impairment. These changes will allow more patients with mild to moderate renal impairment to receive metformin, which is generally the first drug prescribed for treatment of type 2 diabetes. Metformin was previously contraindicated in women with a SCr level ≥1.4 mg/d L and in men with a SCr level ≥1.5 mg/d L, but use of SCr as a surrogate indicator tends to underestimate renal function in certain populations (e.g., younger patients, men, black patients, patients with greater muscle mass). The calculation of e GFR takes into account age, race, and sex, as well as SCr level, providing a more accurate assessment of kidney function. A literature review summarized in an FDA Drug Safety Communication concluded that, based on e GFR, metformin is safe to use in patients with mild renal impairment and in some patients with moderate renal impairment.1The e GFR should be calculated before patients begin treatment with metformin and at least annually thereafter. Metformin is now contraindicated in patients with an e GFR in a patient already taking metformin, the benefits and risks of continuing treatment should be assessed. Dosage increases should be made in increments of 500 mg weekly or 850 mg q2 weeks, up to a total of 2000 mg per day, given in divided doses. Glucophage XR: Starting dose: 500 mg qd with the evening meal. Please review the latest applicable package insert for additional information and possible updates. Dosage increases should be made in increments of 500 mg weekly, up to a maximum of 2000 mg daily with the evening meal. A local search option of this data can be found here. Provides access to the latest drug monographs submitted to the Food and Drug Administration (FDA). The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgment. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user’s use of or reliance upon this material. PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.
They note that any specific value of serum creatinine concentration chosen as a cut-off point for prescribing metformin will be arbitrary because of variations in muscle mass and protein turnover. Despite this they then select—for undefined reasons—a serum creatinine value of 150 μmol/l as the cut-off point in their guideline. Metformin hydrochloride is a white to off-white crystalline compound with a molecular formula of C 4 H 11 N 5 • HCl and a molecular weight of 165.63. Metformin hydrochloride is freely soluble in water and is practically insoluble in acetone, ether, and chloroform.