[Drug interactions with macrolids compared action of two macrolids on liver microsomal activity ]

Pharmacokinetic parameters for elimination of antipyrine, regarded as a marker of the oxidative activity of liver microsomes, were studied in six health volunteers after oral administration of 1 g of the drug. Elimination half life and metabolic clearance were determined prior to (controls) and on day 2 of a treatment with troleandomycin (1500 mg/day), on days 7 and 14 of a treatment with midecamycin (1200 mg/day) and on days 7 and 14 of a treatment with phenobarbital (100 mg/day) as reference. A marked difference was evident between troleandomycin (whose inhibitor effects on the liver metabolism of certain drugs (ergot derivatives, theophylline, etc) are known, and midecamycin. This one had no inhibitor action and this finding is consistent with previous results bearing on the pharmacokinetics of theophylline during antibiotic therapy: only on the 14th day was a slight inductor effect seen, but it remained much lower than that of phenobarbital whose effects were significant on both the 7th and the 14th days.