7 DRUG INTERACTIONS The intravaginal administration of a single dose of metronidazole vaginal gel results in lower systemic exposure to metronidazole that is approximately 2% to 4% of that achieved following oral administration of 500 mg metronidazole tablets [see Clinical Pharmacology ( 12.3 )]. The following drug interactions were reported for oral metronidazole. • Warfarin and other coumarin anticoagulants: Prolonged anticoagulant effects of warfarin and other coumarin anticoagulants have been reported with co-administration of oral metronidazole.
Source: FDA drug label - metronidazole vaginal gel, 1.3 %