Midazolam; Triazolam/Diltiazem; Verapamil Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

If you are taking diltiazem or verapamil, your body may not properly process midazolam or triazolam.

What might happen:

Your blood levels of midazolam or triazolam may increase and cause excess drowsiness.

What you should do about this interaction:

Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. If you experience severe drowsiness or confusion, contact your doctor. It may be necessary to adjust the dose of your medicine or change your medicine.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.Backman JT, Olkkola KT, Aranko K, Himberg JJ, Neuvonen PJ. Dose of midazolam should be reduced during diltiazem and verapamil treatments. Br J Clin Pharmacol 1994 Mar;37(3):221-5.
  • 2.Kosuge K, Nishimoto M, Kimura M, Umemura K, Nakashima M, Ohashi K. Enhanced effect of triazolam with diltiazem. Br J Clin Pharmacol 1997 Apr; 43(4):367-72.
  • 3.Varhe A, Olkkola KT, Neuvonen PJ. Diltiazem enhances the effects of triazolam by inhibiting its metabolism. Clin Pharmacol Ther 1996 Apr; 59(4):369-75.
  • 4.Cardizem LA (diltiazem hcl extended release tablets) US prescribing information. Abbott Pharmaceuticals, Inc. November, 2016.
  • 5.Jones DR, Gorski JC, Hamman MA, Mayhew BS, Rider S, Hall SD. Diltiazem inhibition of cytochrome P-450 3A activity is due to metabolite intermediate complex formation. J Pharmacol Exp Ther 1999 Sep; 290(3):1116-25.
  • 6.Wang JS, Wen X, Backman JT, Taavitsainen P, Neuvonen PJ, Kivisto KT. Midazolam alpha-hydroxylation by human liver microsomes in vitro: inhibition by calcium channel blockers, itraconazole and ketoconazole. Pharmacol Toxicol 1999 Oct;85(4):157-61.
  • 7.Wang YH, Jones DR, Hall SD. Prediction of cytochrome P450 3A inhibition by verapamil enantiomers and their metabolites. Drug Metab Dispos 2004 Feb; 32(2):259-66.