Pentobarbital Alprenolol

Figure 3 Enzyme induction of alprenolol metabolism following pentobarbital treatment produces minimal changes in events in plasma following intravenous administration of alprenolol 5 mg to subjects ( before, during pentobarbital) but a marked lowering of the plasma concentrations following oral administration of alprenolol 200 mg (o before, A during pentobarbital). Source From Ref. 7.

Alvan G, Piafsky K, Lind M, et al. Effect of pentobarbital on the disposition of alprenolol. Clin Pharmacol Ther 1977 22 316-321. 

The interaction between alprenolol and pentobarbital is well documented and likely to be of modest clinical importance when the beta blocker is being used to treat hypertension, and possibly angina. Monitor the effects of alprenolol and increase the dose as necessary. Where possible it may be preferable to replace the barbiturate with a non-interacting alternative, such as one of the benzodiazepines , (p.723), which only have minor effects on the beta blockers, or consider using an alternative non-interacting beta blocker. 

Collste P, Seideman P, Borg K-0, Haglund K, von Bahr C. Influence of pentobarbital on effects and plasma levels of alprenolol and 4-hydroxy-alprenolol. Clin Pharmacol Ther( 919) 25, 423-7. 

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