title: Pharmacokinetic interaction between amprenavir and clarithromycin in healthy male volunteers.
abstract: The P450 enzyme, CYP3A4, extensively metabolizes both amprenavir and clarithromycin. To determine if an interaction exists when these two drugs are coadministered, the pharmacokinetics of amprenavir and clarithromycin were investigated in healthy adult male volunteers. This was a Phase I, open-label, randomized, balanced, multiple-dose, three-period crossover study. Fourteen subjects received the following three regimens: amprenavir, 1,200 mg twice daily over 4 days (seven doses); clarithromycin, 500 mg twice daily over 4 days (seven doses); and the combination of the above regimens over 4 days (seven doses of each drug). Twelve subjects completed all treatments and the follow-up period. The erythromycin breath test (ERMBT) was administered at baseline, 2 h after the final dose of each of the three regimens and at the first follow-up visit. Coadministration of clarithromycin and amprenavir significantly increased the mean amprenavir AUC(ss), C(max,ss), and C(min,ss) by 18, 15, and 39%, respectively. Amprenavir had no significant effect on the AUC(ss) of clarithromycin, but the median T(max,ss)for clarithromycin increased by 2.0 h, renal clearance increased by 34%, and the AUC(ss) for 14-(R)-hydroxyclarithromycin decreased by 35% when it was given with amprenavir. Amprenavir and clarithromycin reduced the ERMBT result by 85 and 67%, respectively, and by 87% when the two drugs were coadministered. The baseline ERMBT value did not correlate with clearance of amprenavir or clarithromycin. A pharmacokinetic interaction occurs when amprenavir and clarithromycin are coadministered, but the effects are not likely to be clinically important, and coadministration does not require a dosage adjustment for either drug.
authors.affiliation: Schools of Pharmacy, Virginia Commonwealth University/Medical College of Virginia Campus, Richmond, VA 23298-0533, USA.
authors.forename: D F
authors.initials: DF
authors.lastname: Brophy
authors.forename: D S
authors.initials: DS
authors.lastname: Israel
authors.forename: A
authors.initials: A
authors.lastname: Pastor
authors.forename: C
authors.initials: C
authors.lastname: Gillotin
authors.forename: G E
authors.initials: GE
authors.lastname: Chittick
authors.forename: W T
authors.initials: WT
authors.lastname: Symonds
authors.forename: Y
authors.initials: Y
authors.lastname: Lou
authors.forename: B M
authors.initials: BM
authors.lastname: Sadler
authors.forename: R E
authors.initials: RE
authors.lastname: Polk
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000493:pharmacokinetics*; D019380:Anti-HIV Agents / Q000009:adverse effects / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001711:Biotransformation; D001944:Breath Tests; D002219:Carbamates; D017291:Clarithromycin / Q000009:adverse effects / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004338:Drug Combinations; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004917:Erythromycin; D005663:Furans; D006207:Half-Life; D006801:Humans; D008111:Liver Function Tests; D008297:Male; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D013449:Sulfonamides / Q000009:adverse effects / Q000493:pharmacokinetics*
chemical_list: D000900:Anti-Bacterial Agents; D019380:Anti-HIV Agents; D002219:Carbamates; D065607:Cytochrome P-450 Enzyme Inhibitors; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D005663:Furans; D013449:Sulfonamides; C095108:amprenavir; D004917:Erythromycin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D017291:Clarithromycin