Metronidazole: Drug-Drug Interactions
Generic Name: Metronidazole
Under what local brands and in what dosages is generic Metronidazole sold in pharmacies of Britain, United States, and Canada?
In pharmacies of the United States, Great Britain and Canada the pharmacists offer you to buy Metronidazole according to your prescription or without a prescription under such brand names and in such strengths and dosage forms (the most popular):
| UK | US | Canada |
| Flagyl 200mg Tablets Flagyl 400mg Tablets Metronidazole 200mg Tablets Metronidazole 400mg Tablets Metronidazole Tablets 500mg | Flagyl 250mg Tablets Flagyl 375mg Capsules Flagyl 500mg Tablets Flagyl ER 750mg Tablets Flagyl I.V. 500mg Injectable | Flagyl 500mg Tablets Flagyl Cream 10% Metrocream 0.75% Cream Metrogel 0.75% & 1% Gel Metronidazole 250mg Tablets |
Alcohol
Metronidazole has a disulfiram-like effect in users of alcohol, sufficient to justify a warning. An unusual Antabuse-type reaction reported on one occasion seems to have been due to an interaction of metronidazole with the alcohol present in X-Prep.
Antibiotics
In vitro, the combination of metronidazole with antibiotics has an additive effect against anaerobic bacteria.
Carbamazepine
Metronidazole can increase the toxicity of carbamazepine by inhibiting its metabolism.
Cephalosporins
The use of high doses of metronidazole in combination with cefamandole and clindamycin has been associated with encephalopathy.
Ciclosporin
An interaction with metronidazole and ciclosporin, in which ciclosporin blood concentrations rise, has been suggested, though only in isolated case histories. It has been confirmed that metronidazole can produce a two-fold increase in blood concentrations of ciclosporin and tacrolimus, with a subsequent increase in serum crea-tinine in both cases. The interaction of metronidazole with ciclosporin significantly increased blood ciclosporin and tacrolimus concentrations in two patients. Since both of these immunosuppressive drugs are toxic in overdosage, and since patients taking them are prone to infections, this is potentially a serious interaction.
Fluorouracil
Pretreatment with metronidazole increased the toxicity of fluorouracil given by a daily bolus dose. The clinical significance of this is yet to be determined.
Gentamicin
In guinea pigs, metronidazole augmented gentamicin-induced ototoxicity, determined by the measurement of compound action potentials.
Lithium
Metronidazole can increase the toxicity of lithium.
Phenytoin
In a patient taking phenytoin, there was a disproportionate increase in the serum concentration of the hydroxylated metabolite of metronidazole, suggesting that phenytoin induces metronidazole-metabolizing enzymes.
Quinidine
Serum quinidine concentrations rose during concomitant administration of metronidazole . The authors speculated that the mechanism was inhibition of cytochrome P450.
Tacrolimus
A possible interaction with metronidazole recently reported is that it significantly increased blood ciclosporin and tacrolimus concentrations in two patients. Since both of these immunosuppressive drugs are toxic in over-dosage, and since patients taking them are susceptible to infections, this is potentially a serious interaction.
Vecuronium bromide
Metronidazole can potentiate the effects of non-depolarizing muscle relaxants. Serum concentrations of metronidazole rose during concomitant administration of ciprofloxacin and metronidazole. The authors speculated that the mechanism was inhibition of cytochrome P450 by ciprofloxacin.
Warfarin and other coumarins
The effect of warfarin is potentiated by metronidazole. The mechanism is stereoselective inhibition by metronidazole of the metabolism of 5-warfarin, the more potent isomer. There is a similar interaction with acenocoumarol.
