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.