prazosin (Rx)

Brand and Other Names:Minipress, Prazin, more...Prazo
  • Print

Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

capsule

  • 1mg
  • 2mg
  • 5mg
more...

Hypertension

Initial: 1 mg PO q8-12hr

Maintenance: 6-15 mg/day divided 2 or 3 times daily; alternatively, 1-5 mg PO BID; may increase dose to 20 mg/day in divided doses; some patients may benefit from up to 40 mg/day in divided doses

PTSD-Related Nightmares & Sleep Disruption (Off-label)

Initial: 1 mg PO qHS

Maintenance: 1 mg PO qHS initially; may increase dose to 2 mg qHS; adjust dose based on response and tolerability in 1-2 mg increments q7days; not to exceed 15 mg/day

Benign Prostate Hypertrophy (Off-label)

Initial: 0.5 mg PO q12hr

Maintenance: 2 mg PO q12hr

Raynaud Phenomenon (Off-label)

0.5-1 mg PO qDay (HS) or 0.5 mg PO BID; adjust dose based on response and tolerability up to 12 mg/day divided BID/TID

Administration

Give first dose and subsequent increases at bedtime to avoid syncope

Okay with food

Dosage Forms & Strengths

capsule

  • 1mg
  • 2mg
  • 5mg
more...

Hypertension (Off-label)

Initial: 0.05-0.1 mg/kg/day PO divided q8hr 

Titrate to 0.5 mg/kg/day; not to exceed 20 mg/day

Administration

Okay with food

Next:

Interactions

Interaction Checker

and prazosin

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

            All Interactions Sort By:
             activity indicator 
            Previous
            Next:

            Adverse Effects

            1-10%

            Dizziness (10%)

            Drowsiness (8%)

            Headache (8%)

            Weakness (7%)

            Asthenia (6.5%)

            Nausea (5%)

            Palpitation (5%)

            Frequency Not Defined (Selected)

            Edema

            Orthostatic hypotension

            Syncope

            Fever

            Rash

            Abdominal discomfort/pain

            Diarrhea

            Vomiting

            Abnormal liver function tests

            Impotence

            Pancreatitis

            Urinary incontinence

            Previous
            Next:

            Warnings

            Contraindications

            Hypersensitivity

            Cautions

            Risk of syncope; has no relation to plasma prazosin concentration; if syncope occurs, place patient in the recumbent position and treat supportively as necessary

            Discontinue if angina symptoms occur or worsen

            May cause CNS depression, which may impair physical or internal abilities; use caution when performing tasks that require mental alertness

            May impair ability to drive/perform hazardous tasks due to dizziness

            History of narcolepsy - May exacerbate

            Cataract surgery - Linked to intraoperative floppy iris syndrome

            Concomitant administration with PDE-5 inhibitor (eg, sildenafil) can result in additive blood pressure-lowering effects and symptomatic hypotension; initiate PDE-5 inhibitor therapy at lowest dose

            First dose effect may occur, causing a sudden and drastic fall in blood pressure after administration of the first dose.

            May exacerbate heart failure

            Prolonged erections and priapism reported with alpha-1 blockers including prazosin in post marketing experience; if erection persists > 4 hours, seek immediate medical assistance

            May cause significant orthostatic hypotension and syncope with sudden loss of consciousness, especially 30-90 min of first dose; may also occur if therapy interrupted for a few days, if dosage rapidly increased or if another antihypertensive drug, like a beta-blocker or vasodilator, or a phosphodiesterase 5 inhibitor is introduced

            Prostatic carcinoma should be ruled out before initiating therapy

            Geriatric considerations

            • Avoid use for hypertension; high risk of orthostatic hypotension (Beers criteria)
            • May cause significant orthostatic hypotension and syncope; consider lower initial dose; titrate to response
            • Adverse effects such as dry mouth and urinary complications can be bothersome in the elderly
            Previous
            Next:

            Pregnancy & Lactation

            Pregnancy category: C

            Lactation: Excreted in breast milk; use caution

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

            more...
            Previous
            Next:

            Pharmacology

            Mechanism of Action

            Alpha-1 blocker inhibits postsynaptic alpha-adrenergic receptors, causing arterial and venous dilation and a subsequent decrease in blood pressure

            Absorption

            Bioavailability: 43-82%

            Onset: ~2 hr

            Duration: 10-24 hr

            Peak effect: 2-4 hr

            Peak plasma time: 2-3 hr

            Distribution

            Protein bound: 97%

            Metabolism

            Hepatic metabolization (extensive)

            Elimination

            Half-life elimination: 2-3 hr

            Excretion: Urine (6-10%); rest in feces (via bile)

            Previous
            Next:

            Images

            Previous
            Next:

            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
            • Manage and view all your plans together – even plans in different states.
            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
            Additional Offers
            Email to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Email Forms to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Previous
            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.