What is prazosin-oral, and how does it work (mechanism of action)?
Prazosin (Minipress) is an oral medicine used to
treat high blood pressure. Prazosin is a competitive alpha-1 adrenergic receptor
blocker. By blocking alpha-1 receptors on muscle cesll that surround blood
vessels, prazosin causes vasodilation (widening) of the blood vessels, and
consequently decreases the resistance of blood flow. The overall benefit of its
use is a decrease in blood pressure.
Prazosin seems to have a bigger impact on reducing the diastolic blood
pressure than systolic blood pressure. Diastolic blood pressure is indicated by
the second set of numbers in the blood pressure reading and corresponds to the
minimum pressure in the arteries when the heart muscles are relaxed and the
chambers of the heart are filling with blood.
Prazosin was approved by the FDA in 1976.
What brand names are available for prazosin-oral?
Is prazosin-oral available as a generic drug?
GENERIC AVAILABLE: Yes
Do I need a prescription for prazosin-oral?
What are the side effects of prazosin-oral?
The most common side effects associated with prazosin treatment
Patients can lower their chance of feeling dizzy or passing out by:
- rising slowing from a sitting or lying position,
- climbing stairs slowly,
- avoiding alcohol, and
- drinking lots of water especially in hot weather or while
Additionally, patients should have their blood pressure checked
Less common side effects include:
- orthostatic hypotension,
- shortness of breath,
- fainting (syncope),
- urinary frequency,
- blurred vision,
- reddened sclera,
dry mouth, and
Rare side effects include:
- stomach pain,
- liver problems,
- tachycardia (fast heartbeat),
- paresthesia (numbness, tingling, burning,
- hair loss,
- urinary incontinence (loss of bladder
- sexual dysfunction,
- prolonged erection,
- ringing in the ears,
- fever, and
- joint pain.
Other side effects reported in post-marketing trials include:
- chest pain,
- low blood pressure,
(enlargement of mens’ breasts, bradycardia [slow heartbeat]),
- vasculitis, and
- eye pain.
Salt and sodium are the same.
What is the dosage for prazosin-oral?
- The dose of prazosin should be adjusted based on the individual patient
- 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
- 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
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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.
Is prazosin-oral safe to take if I’m pregnant or breastfeeding?
There are no adequate and well controlled studies of prazosin use
in pregnancy. Prazosin should be used during pregnancy only if the potential
benefit justifies the potential risk to the mother and the unborn baby. Prazosin
is classified as FDA pregnancy risk category C (adverse effects in animals but
inadequate data in humans).
What else should I know about prazosin-oral?
What preparations of prazosin-oral are available?
Oral capsules: 1, 2, and 5 mg.
How should I keep prazosin-oral stored?
Capsules should be stored at room temperature, between 59 F and 86 F
(15 C and 30 C).