Can grapefruit juice influence ethinylestradiol bioavailability?

Abstract

The effects of grapefruit juice on the bioavailability of 17α-ethinylestradiol (EE 2) after a single oral administration of 50 μg EE 2 have been investigated. The pharmacokinetics of EE 2 were studied in an open, randomized, cross-over study in which 13 healthy volunteers were administered the drug with herbal tea or grapefruit juice (naringin, 887 mg/ml). In contrast to herbal tea, grapefruit juice increased the peak plasma concentration (C max) significantly to 137% (mean; range 64% to 214%, p=0.0088) and increased the area under plasma concentration-time curve from 0 to 8 hours (AUC 0–8) to 128% (mean; range 81% to 180%, p=0.0186). This study shows that grapefruit juice increases the bioavailable amount of EE 2. A possible explanation may be that grapefruit juice inhibits the metabolic degradation of EE 2. Whether the increased bioavailability of EE 2 following grapefruit juice administration is of clinical importance should be investigated in long-term studies.