The Effect of Oral and Injectable Contraceptives (Norethindrone/Ethinyl Estradiol, Medroxyprogesterone Acetate) and Gender on Plasma and Intracellular Zidovudine Pharmacokinetics

Oral contraceptives have been shown to substantially enhance the glucuronidation of several compounds. One study reported enhanced glucuronidation of oxazepam, a compound that is conjugated via the same UDP-glucuronyl transferase isozyme responsible for ADV glucuronidation, suggesting that ZDV metabolism may be altered by concomitant oral contraceptive use. This potential enhancement of ZDV metabolism by oral contraceptives is expected to result in decreased plasma levels of the parent compound which may lead to diminished clinical efficacy in women using these drugs. It remains unclear whether the progesterone and/or estrogen component of oral contraceptives results in the observed glucuronidation changes.

This open-label, pharmacokinetic trial is conducted in 2 steps. [AS PER AMENDMENT 6/12/01: The Depo-Provera IM group in Step 2 is filled. Female patients who choose to participate in Step 2 may enroll only in the Ortho-Novum 1/35 PO group.] [AS PER AMENDMENT 11/13/00: Female patients may choose to participate in Step 1 alone or both Steps 1 and 2.] Male patients may participate in Step 1 only as the control arm of the study. In Step 1, patients are stratified by sex; in Step 2, female patients are stratified by their choice of contraception (i.e., oral norethindrone/ethinyl estradiol [Ortho-Novum 1/35] or injectable medroxyprogesterone acetate [Depo-Provera]).

Step 1 (males and females): At entry, all patients are randomized to receive ZDV either orally or orally and intravenously (IV) on Days 7 and 8. Female patients begin the study (Day 0) between days 10-18 after the first day of their last menstrual period (LMP) (Cycle 1). At time of enrollment, female patients [AS PER AMENDMENT 11/13/00: who plan to participate in Step 2] choose the form of birth control instituted in Step 2: Depo-Provera or Ortho-Novum 1/35. Male patients may enter Step 1 at any time. Patients continue taking their other pre-study antiretroviral drugs during Step 1. [AS PER AMENDMENT 6/3/99: Patients taking nelfinavir may participate only in the Depo-Provera arm.] Days 0-6: All patients receive oral ZDV. Day 7: Patients are randomized to receive:

Arm 1 (females): oral ZDV for a total of 3 doses. Arm 2 (females): ZDV IV, then ZDV orally for a total of 2 oral doses. Arm 3 (males): control arm. Half of the male patients receive ZDV as in Arm 1 and the other male patients receive ZDV as in Arm 2.

Day 8: Patients on all 3 arms receive the alternate form of ZDV to that received on Day 7. Day 9: Female patients resume their pre-study method of administration of ZDV. Male patients conclude their participation in the study on Day 8.