pharmacopeia
GET
/api/v1/drug/prazosin
2D structure
[4-(4-amino-6,7-dimethoxyquinazolin-2-yl)piperazin-1-yl]-(furan-2-yl)methanone
SMILES COC1=C(C=C2C(=C1)C(=NC(=N2)N3CCN(CC3)C(=O)C4=CC=CO4)N)OC
InChIKey IENZQIKPVFGBNW-UHFFFAOYSA-N

Mechanism of action

Sourced from openFDA

Mechanism-of-action class: Adrenergic alpha-Antagonists.

Indications

Sourced from openFDA
  • Prazosin hydrochloride capsules are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions.ICD-10: I10

Contraindications

Sourced from openFDA
  • Prazosin hydrochloride capsules are contraindicated in patients with known sensitivity to quinazolines, prazosin, or any of the inert ingredients.contraindicated

Dosage & administration

Sourced from openFDA

The dose of prazosin hydrochloride capsules should be adjusted according to the patient’s individual blood pressure response. The following is a guide to its administration: Initial Dose 1 mg two or three times a day (see WARNINGS. ) Maintenance Dose Dosage may be slowly increased to a total daily dose of 20 mg given in divided doses. The therapeutic dosages most commonly employed have ranged from 6 mg to 15 mg daily given in divided doses. Doses higher than 20 mg usually do not increase efficacy, however a few patients may benefit from further increases up to a daily dose of 40 mg given in divided doses. After initial titration some patients can be maintained adequately on a twice daily dosage regimen. Use With Other Drugs When adding a diuretic or other antihypertensive agent, the dose of prazosin hydrochloride capsules should be reduced to 1 mg or 2 mg three times a day and retitration then carried out. Concomitant administration of prazosin hydrochloride capsules with a PDE-5 inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension; therefore, PDE-5 inhibitor therapy should be initiated at the lowest dose in patients taking prazosin hydrochloride capsules.

Warnings & precautions

Sourced from openFDA

As with all alpha-blockers, prazosin hydrochloride may cause syncope with sudden loss of consciousness. In most cases, this is believed to be due to an excessive postural hypotensive effect, although occasionally the syncopal episode has been preceded by a bout of severe tachycardia with heart rates of 120 to 160 beats per minute. Syncopal episodes have usually occurred within 30 to 90 minutes of the initial dose of the drug; occasionally, they have been reported in association with rapid dosage increases or the introduction of another antihypertensive drug into the regimen of a patient taking high doses of prazosin hydrochloride. The incidence of syncopal episodes is approximately 1% in patients given an initial dose of 2 mg or greater. Clinical trials conducted during the investigational phase of this drug suggest that syncopal episodes can be minimized by limiting the initial dose of the drug to 1 mg, by subsequently increasing the dosage slowly, and by introducing any additional antihypertensive drugs into the patient’s regimen with caution (see DOSAGE AND ADMINISTRATION ) . Hypotension may develop in patients given prazosin hydrochloride who are also receiving a beta-blocker such as propranolol. If syncope occurs, the patient should be placed in the recumbent position and treated supportively as necessary. This adverse effect is self-limiting and in most cases does not recur after the initial period of therapy or during subsequent dose titration. Patients should always be started on the 1 mg capsules of prazosin hydrochloride.

Adverse reactions

Sourced from openFDA

Clinical trials were conducted on more than 900 patients. During these trials and subsequent marketing experience, the most frequent reactions associated with prazosin hydrochloride therapy are: dizziness 10.3%, headache 7.8%, drowsiness 7.6%, lack of energy 6.9%, weakness 6.5%, palpitations 5.3%, and nausea 4.9%. In most instances, side effects have disappeared with continued therapy or have been tolerated with no decrease in dose of drug. Less frequent adverse reactions which are reported to occur in 1 to 4% of patients are: Gastrointestinal: vomiting, diarrhea, constipation. Cardiovascular: edema, orthostatic hypotension, dyspnea, syncope. Central Nervous System: vertigo, depression, nervousness. Dermatologic: rash. Genitourinary: urinary frequency. EENT: blurred vision, reddened sclera, epistaxis, dry mouth, nasal congestion. In addition, fewer than 1% of patients have reported the following (in some instances, exact causal relationships have not been established): Gastrointestinal: abdominal discomfort and/or pain, liver function abnormalities, pancreatitis. Cardiovascular: tachycardia. Central Nervous System: paresthesia, hallucinations. Dermatologic: pruritus, alopecia, lichen planus. Genitourinary: incontinence, impotence, priapism. EENT: tinnitus. Other: diaphoresis, fever, positive ANA titer, arthralgia. Single reports of pigmentary mottling and serous retinopathy, and a few reports of cataract development or disappearance have been reported.

Use in specific populations

Sourced from openFDA

Usage in Pregnancy: Pregnancy Category C. Prazosin hydrochloride has been shown to be associated with decreased litter size at birth, 1, 4, and 21 days of age in rats when given doses more than 225 times the usual maximum recommended human dose. No evidence of drug-related external, visceral, or skeletal fetal abnormalities were observed. No drug-related external, visceral, or skeletal abnormalities were observed in fetuses of pregnant rabbits and pregnant monkeys at doses more than 225 times and 12 times the usual maximum recommended human dose, respectively. The use of prazosin and a beta-blocker for the control of severe hypertension in 44 pregnant women revealed no drug-related fetal abnormalities or adverse effects. Therapy with prazosin was continued for as long as 14 weeks. 1 Prazosin has also been used alone or in combination with other hypotensive agents in severe hypertension of pregnancy by other investigators. No fetal or neonatal abnormalities have been reported with the use of prazosin. 2 There are no adequate and well controlled studies which establish the safety of prazosin hydrochloride in pregnant women. Prazosin hydrochloride should be used during pregnancy only if the potential benefit justifies the potential risk to the mother and fetus.

Overdosage

Sourced from openFDA

Accidental ingestion of at least 50 mg of prazosin hydrochloride in a two year old child resulted in profound drowsiness and depressed reflexes. No decrease in blood pressure was noted. Recovery was uneventful. Should overdosage lead to hypotension, support of the cardiovascular system is of first importance. Restoration of blood pressure and normalization of heart rate may be accomplished by keeping the patient in the supine position. If this measure is inadequate, shock should first be treated with volume expanders. If necessary, vasopressors should then be used. Renal function should be monitored and supported as needed. Laboratory data indicate prazosin hydrochloride is not dialysable because it is protein bound.

Approval history

Sourced from openFDA
  • Jun 23, 1976NDANDA017442Pfizer
  • Sep 12, 1988ANDAANDA071745Teva Pharms
  • Feb 28, 1989ANDAANDA072575Mylan
  • Oct 3, 2018ANDAANDA210971Novitium Pharma
  • Dec 23, 2021ANDAANDA214608Granules
  • Oct 21, 2022ANDAANDA213406Appco
  • Dec 30, 2022ANDAANDA215697Mankind Pharma
  • Mar 6, 2023ANDAANDA217268Alembic

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
7,175 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Drug Ineffective4716.6%
  2. 2Off Label Use4576.4%
  3. 3Nausea4516.3%
  4. 4Fatigue3625.0%
  5. 5Headache3304.6%
  6. 6Pain3194.4%
  7. 7Dizziness3144.4%
  8. 8Anxiety3014.2%
  9. 9Diarrhoea2984.2%
  10. 10Vomiting2954.1%
  11. 11Depression2833.9%
  12. 12Dyspnoea2733.8%
  13. 13Fall2633.7%
  14. 14Hypotension2593.6%
  15. 15Drug Interaction2463.4%

Literature

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Recent PubMed references pinned to Prazosin as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 10 most recently updated of 125 ClinicalTrials.gov registrations naming Prazosin as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Prazosin work?
Mechanism-of-action class: Adrenergic alpha-Antagonists.
What is Prazosin used for?
According to FDA labeling, Prazosin carries indications including: Prazosin hydrochloride capsules are indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Prazosin?
Prazosin is classified as Alpha-adrenoreceptor antagonists, alpha-Adrenergic Blocker, Adrenergic alpha-Antagonists, Arterial Vasodilation, Decreased Bladder Sphincter Tone, Decreased Blood Pressure, Venous Vasodilation.
What are the brand names for Prazosin?
Prazosin is marketed under brand names including Minipress.
What are the contraindications for Prazosin?
Prazosin labeling lists contraindications including: Prazosin hydrochloride capsules are contraindicated in patients with known sensitivity to quinazolines, prazosin, or any of the inert ingredients.. Always consult the full prescribing information and a clinician.
Note. Data for prazosin is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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