Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
The barbiturate may increase how quickly your body processes the beta-blocker.
What might happen:
The effects of the beta-blocker will be decreased. You may have an increased pulse and your blood pressure may be increased.
What you should do about this interaction:
If you are taking the beta-blocker to decrease your blood pressure, monitor your blood pressure when taking these medications together. The effects of this interaction are usually seen after taking the medicines together for four or five days.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Alvan G, Piafsky K, Lind M, von Bahr C. Effect of pentobarbital on the disposition of alprenolol. Clin Pharmacol Ther 1977 Sep;22(3):316-21.
2.Alvan G, Lind M, Mellstrom B, von Bahr C. Importance of "first-pass elimination" for interindividual differences in steady-state concentrations of the adrenergic beta-receptor antagonist alprenolol. J Pharmacokinet Biopharm 1977 Jun;5(3):193-205.
3.Collste P, Seideman P, Borg KO, Haglund K, von Bahr C. Influence of pentobarbital on effect and plasma levels of alprenolol and 4-hydroxy-alprenolol. Clin Pharmacol Ther 1979 Apr;25(4):423-7.
4.Sotaniemi EA, Anttila M, Pelkonen RO, Jarvensivu P, Sundquist H. Plasma clearance of propranolol and sotalol and hepatic drug- metabolizing enzyme activity. Clin Pharmacol Ther 1979 Aug;26(2):153-61.
5.Haglund K, Seideman P, Collste P, Borg KO, von Bahr C. Influence of pentobarbital on metoprolol plasma levels. Clin Pharmacol Ther 1979 Sep; 26(3):326-9.
6.Mantyla R, Mannisto P, Nykanen S, Koponen A, Lamminsivu U. Pharmacokinetic interactions of timolol with vasodilating drugs, food and phenobarbitone in healthy human volunteers. Eur J Clin Pharmacol 1983;24(2):227-30.
7.Branch RA, Herman RJ. Enzyme induction and beta-adrenergic receptor blocking drugs. Br J Clin Pharmacol 1984;17 Suppl 1:77S-84S.
8.Seideman P, Borg KO, Haglund K, Von Bahr C. Decreased plasma concentrations and clinical effects of alprenolol during combined treatment with pentobarbitone in hypertension. Br J Clin Pharmacol 1987 Mar;23(3):267-71.