Metfor XR Drug Interactions

500 mg: Concomitant use not recommended: Alcohol: Alcohol consumption increases the risk of lactic acidosis, especially when combined with fasting, malnutrition, or hepatic impairment.
Iodinated contrast agents: Metformin must be stopped prior to or during the imaging process and not reintroduced for at least 48 hours, assuming renal function has been re-evaluated and determined to be stable.
Combinations requiring precautions for use: Some medications can impair renal function and hence raise the risk of lactic acidosis, for example, NSAIDs, such as selective cyclo-oxygenase (COX) II inhibitors, ACE inhibitors, angiotensin II receptor antagonists, and diuretics, particularly loop diuretics. Close monitoring of renal function is required while starting or using such drugs in conjunction with metformin.
Medicinal products with intrinsic hyperglycemic activity (e.g. glucocorticoids (systemic and local routes) and sympathomimetics).
More frequent blood glucose testing may be necessary, particularly at the start of treatment. Adjust the metformin dosage as needed during the therapy of other drugs and after its discontinuation.
Organic cation transporters (OCT): Metformin is a substrate of both transporters OCT1 and OCT2. Co-administration of metformin with: Inhibitors of OCT1 (such as verapamil) may lessen metformin efficacy.
Inducers of OCT1 (such as rifampicin) may enhance gastrointestinal absorption and efficacy of metformin.
Inhibitors of OCT2 (such as cimetidine, dolutegravir, ranolazine, trimethoprim, vandetanib, isavuconazole) may reduce the renal elimination of metformin and therefore lead to an enhanced metformin plasma concentration.
Inhibitors of both OCT1 and OCT2 (such as crizotinib, olaparib) may change efficacy and renal elimination of metformin.
Therefore, caution is advised, especially in patients with renal impairment, when these drugs are administered together with metformin, as metformin plasma concentration may increase. If needed, dose adjustment of metformin may be considered as OCT inhibitors/inducers may change the efficacy of metformin.
750 mg: Contraindicated combinations: In patients with CrCl below 45 mL/min or eGFR below 45 mL/min/1.73 m² for intravenous administration or in patients with CrCl below 45 mL/min or eGFR below 60 mL/min/1.73 m² for intra-arterial administration of iodinated contrast materials, metformin must be discontinued 48 hours before the test (see Contraindications).
Combinations to be used with caution: Medicinal products with intrinsic hyperglycemic activity (e.g. glucocorticoids and tetracosactides [systemic and local routes], beta-2-agonists, danazol, and chlorpromazine at high dosages of 100 mg per day, diuretics): More frequent blood glucose monitoring may be required, especially at the beginning of treatment. If necessary, adjust the metformin dosage during therapy with the respective medicinal product and upon its discontinuation. Diuretics, especially loop diuretics, may increase the risk of lactic acidosis due to their potential to decrease renal function (further to their intrinsic hyperglycemic effect).
Organic cation transporters (OTC): Metformin is a substrate of both transporters OCT1 and OCT2. Co-administration of metformin with: Substrates/inhibitors of OCT1 (such as verapamil) may reduce efficacy of metformin.
Inducers of OCT1 (such as rifampicin) may increase gastrointestinal absorption and efficacy.
Substrates/inhibitors of OCT2 (such as cimetidine, dolutegravir, crizotinib, olaparib, daclatasvir, vandetanib) may decrease the renal elimination of metformin and thus lead to an increase in metformin plasma concentration.
Other interactions: Nifedipine appears to enhance the absorption of metformin.
Cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, or vancomycin) could potentially interact with metformin by competing for common renal tubular transport systems.
Cimetidine increases peak plasma concentration of metformin and whole blood concentrations.
Certain drugs such as thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid, tend to produce hyperglycemia and may lead to loss of glycemic control. Monitor closely for loss of blood glucose control in patients taking these drugs. When such drugs are withdrawn from a patient receiving metformin, the patient should be closely observed for hypoglycemia.