Premium
The erythromycin breath test as a predictor of cyclosporine blood levels
Author(s) -
Watkins Paul B,
Hamilton Ted A,
Annesley Thomas M,
Ellis Charles N,
Kolars Joseph C,
Voorhees John J
Publication year - 1990
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1990.126
Subject(s) - erythromycin , dosing , pharmacology , medicine , clinical pharmacology , psoriasis , pharmacokinetics , drug interaction , antibiotics , chemistry , immunology , biochemistry
The daily dose of cyclosporine required to attain a desired blood level can vary greatly among patients. Because elimination of cyclosporine depends on its metabolism in the liver by an enzyme (cytochrome P‐450IIIA) that also demethylates erythromycin, we reasoned that the ability of patients to demethylate a test dose of erythromycin might be useful in estimating their appropriate daily doses of cyclosporine. Accordingly, the [ 14 C‐ N ‐methyl] erythromycin breath test was administered to 32 patients before they received 3.0, 5.0, or 7.5 mg/kg/day cyclosporine to treat psoriasis. We found that a simple mathematical equation incorporating just the 14 CO 2 production, the age of the patient, and the daily dose of cyclosporine accounted for almost 80% ( R 2 = 0.78) of the interpatient variability in cyclosporine blood levels we observed. Our data indicate that P‐450IIIA activity largely accounts for the relationship between dose of cyclosporine and blood levels for an individual patient. We conclude that the erythromycin breath test may be a convenient guide for cyclosporine dosing. Clinical Pharmacology and Therapeutics (1990) 48, 120–129; doi: 10.1038/clpt.1990.126