CGMP Specific PDE Type-5 Inhibitors/Alpha-Blockers 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:

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:

Avanafil, sildenafil, tadalafil, vardenafil, and alpha-blockers can lower your blood pressure.

What might happen:

Taking avanafil, sildenafil, tadalafil, or vardenafil with an alpha-blocker may result in your blood pressure becoming too low.If your blood pressure is too low, you may feel faint, dizzy, or lose consciousness.

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 have been taking an alpha-blocker, your doctor may want you to wait to start taking avanafil, sildenafil, tadalafil, or vardenafil until you have adjusted to your alpha-blocker.If you have been taking avanafil, sildenafil, tadalafil, or vardenafil, your doctor may start you on a lower dose of an alpha-blocker.Your doctor may instruct you to separate the times you take your avanafil, sildenafil, tadalafil, or vardenafil from the time you take your alpha-blocker.Let your healthcare professionals know if you experience any dizziness or fainting.Your healthcare professionals 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.Viagra (sildenafil) US prescribing information. Pfizer Inc. December 14, 2017.
  • 2.Viagra (sildenafil) Australian prescribing information. Pfizer October 17, 2006.
  • 3.Viagra (sildenafil citrate) Canadian prescribing information. Pfizer March 9, 2006.
  • 4.Viagra (sildenafil citrate) UK summary of product characteristics. Pfizer Limited July 11, 2006.
  • 5.Cialis (tadalafil) US prescribing information. Eli Lilly and Company February, 2018.
  • 6.Cialis (tadalafil) Australian prescribing information. Eli Lilly Pty Ltd July 3, 2006.
  • 7.Cialis (tadalafil) Canadian prescribing information. Lilly August 30, 2005.
  • 8.Cialis (tadalafil) UK summary of product characteristics. Eli Lilly and Company Limited September 16, 2008.
  • 9.Levitra (vardenafil hydrochloride) US prescribing information. Bayer Pharmaceuticals Corporation September, 2015.
  • 10.Levitra (vardenafil hydrochloride) Canadian prescribing information. Bayer, Inc. October 24, 2006.
  • 11.Levitra (vardenafil hydrochloride trihydrate) UK summary of product characteristics. Bayer plc December 20, 2006.
  • 12.Levitra (vardenafil hydrochloride trihydrate) Australian prescribing information. Bayer Australia Limited November 2, 2006.
  • 13.Cardura (doxazosin hydrochloride) US prescribing information. Pfizer, Inc. June, 2016.
  • 14.Minipress (prazosin hydrochloride) US prescribing information. Pfizer Inc. February, 2015.
  • 15.Hytrin (terazosin hydrochloride) US prescribing information. Abbott Laboratories July, 2009.
  • 16.Kloner RA, Jackson G, Emmick JT, Mitchell MI, Bedding A, Warner MR, Pereira A. Interaction between the phosphodiesterase 5 inhibitor, tadalafil and 2 alpha-blockers, doxazosin and tamsulosin in healthy normotensive men. J Urol 2004 Nov;172(5 Pt 1):1935-40.
  • 17.Auerbach SM, Gittelman M, Mazzu A, Cihon F, Sundaresan P, White WB. Simultaneous administration of vardenafil and tamsulosin does not induce clinically significant hypotension in patients with benign prostatic hyperplasia. Urology 2004 Nov;64(5):998-1003; discussion 1003-4.
  • 18.Rapaflo (silodosin) US prescribing information. Watson Laboratories, Inc. July, 2013.

Selected from data included with permission and copyrighted by First Databank, Inc. This copyrighted material has been downloaded from a licensed data provider and is not for distribution, except as may be authorized by the applicable terms of use.

CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.