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 cause of the interaction is unknown. Beta-blockers may increase the chance that you will have a sudden decrease in your blood pressure when starting your prazosin.
What might happen:
You may experience a sudden decrease in your blood pressure when starting prazosin, if you are already taking a beta-blocker. This problem may be worsened if you are also taking a water pill (e.g. a diuretic) or are on a low salt diet.
What you should do about this interaction:
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.Elliott HL, McLean K, Sumner DJ, Meredith PA, Reid JL. Immediate cardiovascular responses to oral prazosin--effects of concurrent beta-blockers. Clin Pharmacol Ther 1981 Mar;29(3):303-9.
2.Graham RM, Thornell IR, Gain JM, Bagnoli C, Oates HF, Stokes GS. Prazosin: the first-dose phenomenon. Br Med J 1976 Nov 27;2(6047):1293-4.
3.Rubin P, Jackson G, Blaschke T. Studies on the clinical pharmacology of prazosin. II: The influence of indomethacin and of propranolol on the action and disposition of prazosin. Br J Clin Pharmacol 1980 Jul; 10(1):33-9.
4.Seideman P, Grahnen A, Haglund K, Lindstrom B, Von Bahr C. Prazosin first dose phenomenon during combined treatment with a beta- adrenoceptor blocker in hypertensive patients. Br J Clin Pharmacol 1982 Jun; 13(6):865-70.