Zidovudine had no effect on methadone levels in one study, but there is one report of
a patient requiring a modest increase in his methadone dose after starting zidovudine.
Similarly, small changes in the
pharmacokinetics of abacavir and methadone may occur on concurrent use, and there is a report of 2 patients requiring increases in their methadone doses. Methadone can increase zidovudine
serum levels, and reduce levels of didanosine from the tablet formulation, but not the enteric-coated capsule preparation. Methadone may cause small decreases in stavudine levels.
The
clinical relevance of these minor changes is unclear. It may be prudent to
monitor methadone dose requirements until more is known.