The analgesic effects of
codeine, and hydrocodone appear to be reduced or abolished by
quinidine in most patients.
Quinidine appears to increase the oral absorption and effects of fentanyl, methadone, and morphine.
The interaction with
codeine, and hydrocodone is possible in the majority of patients. Consider the use of an alternative analgesic. Dihydrocodeine, oxycodone and tramadol do not appear to be affected. Monitor for increased opioid effects after the oral
administration of fentanyl, methadone, and morphine. Note that
quinidine and high-dose methadone may prolong the QT interval, see drugs that prolong the QT interval.