prazosin (Minipress)

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What is the dosage for prazosin-oral?

  • The dose of prazosin should be adjusted based on the individual patient response.
  • For the treatment of high blood pressure: Most patients are started with 1 mg by mouth 2-3 times a day. To decrease the risk of orthostatic hypotension the first dose may be given at bedtime. Orthostatic hypotension is a drop in blood pressure when standing up from a sitting or lying position. Dosage may be increased gradually over time to a total daily dose of 20 mg given in multiple doses.
  • If adding another blood pressure lowering agent or water pill (diuretic) to prazosin therapy, the dose of prazosin should be reduced to 1-2 mg by mouth three times a day, followed by slow increases in dose as needed.
  • As elderly patients are more sensitive to the side effects of low blood pressure, dose reduction in the elderly is necessary. Most elderly patients are started on 1 mg by mouth 1-2 times daily.
  • The safety and effectiveness of prazosin in children has not been established.

Which drugs or supplements interact with prazosin-oral?

Use of prazosin with other blood pressure lowering medicines or water pills may cause an additive blood pressure lowering effect.

Use of phosphodiesterase-5 (PDE-5) inhibitors, for example, sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) with prazosin can also cause an additive decrease in blood pressure. To decrease the risk of precipitating side effects associated with low blood pressure, the lowest possible dose of PDE-5 inhibitors should be used in patients taking prazosin.

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