Title

The effect of rifampin on theophylline kinetics

ORCiD

Eric Boyce: 0000-0002-5447-9016

Document Type

Poster

Conference Title/Conference Publication

American Society for Clinical Pharmacology & Therapeutics

Location

San Antonio, TX

Conference Dates

March 28-30, 1985

Date of Presentation

3-30-1985

ISSN

2572-6803

Abstract

The influence of rifampin (R) on the pharmacokinetics of theophylline (T) was studied in 10 healthy nonsmoking males (age 23-42 yrs). Each subject received 5.9 to 6.8 mg/kg of aminophylline (IV over 20 min.) before and at the end of 2 weeks of R administration (600 mg/day orally). T serum concentrations were measured serially over the 24-hour period following each aminophyl- line infusion. In every subject, R caused an increase in the clearance rate (from a mean± S.D. of 0.88±0.21 to 1.21±0.29 ml/min/kg) and the terminal elimination rate constant of T (from 0.104±0.023 to 0.149± 0.029 hrs-1), and a decrease in the area under the T serum concentration vs. time curve (from 104±29 to 76±19 mg-hrs/L) and T half-life (from 7.0±1.7 to 4.8±0.9 hrs). These changes were statistically significant (p<.02). The terminal-phase volume of distribution did not consistently change following R (mean percentage change -1%, range +19 to -19%, p>.27). These results suggest that R causes an increase in the elimination rate of T. Patients should be monitored for signs of decreased efficacy from T when R is added, or of increased T toxicity when R is discontinued from maintenance therapy.

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