Possible Interaction: Quinidine and Tramadol

“ Quinidine blockade of tramadol myosis suggests that the mu agonist component of tramadol effect results from its O-demethylation by the polymorphic P450DB1 enzyme.”

“ Quinidine had no effect on the extent of tramadol analgesia, but inhibited tramadol induced myosis.”

“It should be taken into account that inducers (e.g. carbamazepine) or inhibitors (e.g. quinidine for CY2D6) of drug metabolism might modify the elimination of tramadol.”

“ Tramadol metabolism in human liver microsomes to M1 and M2 was markedly inhibited by the CYP2D6 inhibitor quinidine and the CYP3A4 inhibitor troleandomycin, respectively.”

“Following allosteric inhibition by a single dose of quinidine , the exposure of both tramadol (51% increase) and O-desmethyltramadol (52% decrease) was predicted to be significantly altered after concomitant administration of a single dose of tramadol.”

“Following multiple-… administration of tramadol and a single-dose … multiple-dose administration of quinidine , the inhibitory effect of quinidine was predicted to be long (∼42h) and to alter exposure of tramadol and …-desmethyltramadol by up to 60%, suggesting that co-administration of quinidine and tramadol should be avoided clinically.”