Pharmacokinetic changes of theophylline and amikacin through the menstrualcycle in healthy women

The objective of this open-label, single-dose study was to clarify the infl uence of the menstrual cycle an the pharmacokinetics of theophylline (n = 1 0) and amikacin (n = 8) in young healthy Japanese women with regular menstr ual cycles. Each subject received an intravenous infusion of theophylline o r amikacin sulfate at four difference phases-mid-follicular (phase I), peri -ovulatory (phase II), mid-luteal (phase III), and premenstrual days (phase IV). In the theophylline study, there were no significant differences in t he pharmacokinetic parameters among the four phases studied In the amikacin study, CLtot was 15% higher in phase III than in phase I (p < 0.01). V-d b eta was 35% higher in phase III than in phase I (p < 0.05). The other pharm acokinetic parameters of amikacin were not significantly altered during the menstrual cycle. Evidence suggests that the phase of the menstrual cycle m ay be a factor in determining the pharmacokinetics of amikacin. (C) 1999 th e American College of Clinical pharmacology.