title: Interferon suppresses erythromycin metabolism in rats and human subjects.
abstract: Interferon down-regulates expression of cytochrome P-450 3A in male rats. This study explored the hypothesis that interferon therefore decreases the metabolism of drugs catalyzed by cytochrome P-450 3A. Initial experiments in male rats used microsomal erythromycin N-demethylase activity as a probe for cytochrome P-450 3A catalytic activity. After administration of rat interferon-gamma, erythromycin metabolism was impaired (53% of control; p < 0.01). This change correlated with the decline in cytochrome P-450 3A-dependent androstenedione 6 beta-hydroxylase activity, indicating that the decrease in erythromycin N-demethylase activity could be attributed to interferon-mediated suppression of cytochrome P-450 3A. We then used the [14C]N-methyl erythromycin breath test to assess the activity of hepatic cytochrome P-450 3A in rats and human subjects before and after a single dose of interferon. In rats, rat interferon-gamma decreased erythromycin metabolism to 57% of control (p < 0.005). In the human study, six patients with chronic active hepatitis C and four healthy controls were examined 20 to 26 hr after receiving a subcutaneous injection of human interferon-alpha 2b. Interferon produced a small decrease (median = 15%; range = 3% to 35%) in erythromycin metabolism (p < 0.05), as determined by 2-hr excretion of 14CO2 in the breath. Thus interferon-mediated suppression of cytochrome P-450 3A is less strong in human subjects than in male rats.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Sydney, Westmead Hospital, New South Wales, Australia.
authors.forename: P I
authors.initials: PI
authors.lastname: Craig
authors.forename: M
authors.initials: M
authors.lastname: Tapner
authors.forename: G C
authors.initials: GC
authors.lastname: Farrell
mesh_terms: D000328:Adult; D000818:Animals; D002908:Chronic Disease; D004917:Erythromycin / Q000378:metabolism*; D005260:Female; D006526:Hepatitis C / Q000378:metabolism; D006801:Humans; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology; D007372:Interferons / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins; D012016:Reference Values
chemical_list: D000077190:Interferon alpha-2; D016898:Interferon-alpha; D011994:Recombinant Proteins; D004917:Erythromycin; D007372:Interferons