Biguanide
Metformin with antibiotics: interactions and safety
Antibiotic courses are common, short-term and often combined with chronic medications such as Metformin (Metformin). Most antibiotics do not interfere meaningfully with Metformin at 500mg, 850mg, 1000mg, but a few classes do, and a small number of combinations are best avoided.
Common antibiotic interactions
Macrolides (clarithromycin, erythromycin) and certain antifungals can inhibit hepatic metabolism (CYP3A4) and raise plasma levels of many medications including some Biguanide agents. Rifampicin has the opposite effect, accelerating metabolism. Most penicillins, cephalosporins, fluoroquinolones and tetracyclines have no clinically meaningful interaction with Metformin at 500mg, 850mg, 1000mg.
Practical guidance
According to the prescribing information for Metformin, an antibiotic course should be reviewed by the prescriber or pharmacist for known interactions before Metformin is co-administered. Adjusted 500mg, 850mg, 1000mg dosing or temporary substitution is sometimes preferred for the duration of the antibiotic course.
Frequently asked questions
Can I take Metformin during an antibiotic course? ▾
For most common antibiotics, yes. A few classes — notably macrolides and azole antifungals — alter how Metformin is metabolised and may need a temporary 500mg, 850mg, 1000mg adjustment. The prescribing pharmacist should review any new antibiotic against the existing Metformin regimen.
Will antibiotics make Metformin stop working? ▾
Most antibiotics do not affect Metformin efficacy. Rifampicin and a few others can lower Metformin levels and reduce effect; in those cases the prescriber may adjust the dose during and shortly after the antibiotic course.
Products containing Metformin
More on Metformin
- With alcoholMetformin and alcohol — is it safe to drink?
- With foodShould Metformin be taken with food?
- Side effectsMetformin side effects: common, rare and warning signs
- Dosage guideMetformin dosage guide: how much to take and when
- OnsetHow fast does Metformin start working?
- DurationHow long does Metformin last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.