Drug · FAERS side-effect profile with label screen
Prazosin side effects: what 6,095 FDA adverse event reports show
Drug class
Not stated in label
Who reports
6,095 reports · 74% serious · 711 with death outcome · 58% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Prazosin hydrochloride is 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. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes, including this drug.
FDA label, Indications and Usage
What it is
DESCRIPTION Prazosin Hydrochloride Capsules, USP, a quinazoline derivative, is the first of a new chemical class of antihypertensives. It is the hydrochloride salt of 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-furoyl) piperazine and its structural formula is:
FDA label, Description section
Boxed warning
None in the current label
How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation.
Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)?
That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.
Causality screen of the 40 strongest signals
Likely indication confounding 4Reporting / coding artifact 3Lab value / disease marker 4Outcome field, not a reaction 1Not in label — unassessed 28
What the badges mean
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- Outcome field, not a reaction Death is a report outcome, not a reaction term. It is dominated by the underlying illness; see the seriousness profile and the boxed warning instead.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 462 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Cardiogenic shock | 71 | 17.2 13.6–21.7ROR 17.4 · χ² 1,062 / p 4e-233 | 17.0 EB05 13.9 · IC025 +3.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 13.3 · 97% clinician | no trial data cached |
| Sinus bradycardia | 47 | 16.8 12.6–22.3ROR 16.9 · χ² 678 / p 1e-149 | 16.5 EB05 12.9 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious PRR 13.3 · 93% clinician | no trial data cached |
| Serotonin syndrome | 72 | 13.0 10.3–16.3ROR 13.1 · χ² 782 / p 2e-172 | 12.8 EB05 10.4 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 10.0 · ♀ 12% (drug 58%) · 93% clinician | no trial data cached |
| Impaired gastric emptying | 46 | 12.4 9.3–16.6ROR 12.5 · χ² 471 / p 9e-105 | 12.1 EB05 9.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 10.8 · 74% consumer | no trial data cached |
| Hypertensive crisis | 37 | 11.4 8.3–15.8ROR 11.5 · χ² 341 / p 2e-76 | 10.9 EB05 8.1 · IC025 +2.8 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 8.9 | no trial data cached |
| Vitamin d deficiency | 30 | 10.6 7.4–15.2ROR 10.7 · χ² 251 / p 8e-57 | 9.9 EB05 7.1 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 8.9 · ♀ 100% (drug 58%) · 100% clinician | no trial data cached |
| Brain injury | 30 | 10.3 7.2–14.7ROR 10.4 · χ² 242 / p 7e-55 | 9.6 EB05 6.8 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 8.1 · ♀ 86% (drug 58%) | no trial data cached |
| Spinal disorder | 27 | 9.8 6.7–14.3ROR 9.8 · χ² 204 / p 1e-46 | 9.0 EB05 6.3 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 8.8 · ♀ 100% (drug 58%) | no trial data cached |
| Pulmonary congestion | 36 | 9.4 6.8–13.0ROR 9.4 · χ² 260 / p 7e-59 | 8.8 EB05 6.5 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 7.7 · ♀ 0% (drug 58%) | no trial data cached |
| Nightmare | 92 | 9.1 7.4–11.2ROR 9.2 · χ² 656 / p 4e-145 | 8.9 EB05 7.4 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 7.7 | no trial data cached |
| Electrocardiogram qt prolonged | 94 | 9.0 7.4–11.0ROR 9.1 · χ² 660 / p 8e-146 | 8.8 EB05 7.3 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 7.1 · 93% clinician | no trial data cached |
| Neutrophil count increased | 26 | 8.7 5.9–12.8ROR 8.7 · χ² 170 / p 5e-39 | 7.9 EB05 5.5 · IC025 +2.3 3/3 methods agree | Lab value / disease marker | serious PRR 7.1 · ♀ 90% (drug 58%) · 100% clinician | no trial data cached |
| Suicidal ideation (thoughts of suicide) | 228 | 8.6 7.5–9.7ROR 8.9 · χ² 1,520 / p <1e-300 | 8.5 EB05 7.6 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 6.6 | no trial data cached |
| Temperature intolerance | 25 | 8.4 5.7–12.5ROR 8.5 · χ² 156 / p 4e-36 | 7.6 EB05 5.3 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious n=23 · ♀ 85% (drug 58%) | no trial data cached |
| Completed suicide (death by suicide) | 205 | 8.4 7.3–9.6ROR 8.7 · χ² 1,330 / p 2e-291 | 8.3 EB05 7.4 · IC025 +2.8 3/3 methods agree | Outcome field, not a reaction | serious PRR 6.5 · 95% clinician | no trial data cached |
| Sinus tachycardia | 33 | 8.0 5.7–11.3ROR 8.1 · χ² 196 / p 1e-44 | 7.4 EB05 5.4 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 6.3 · ♀ 87% (drug 58%) · 100% clinician | no trial data cached |
| Generalised tonic-clonic seizure | 35 | 7.4 5.3–10.3ROR 7.4 · χ² 186 / p 1e-42 | 6.8 EB05 5.1 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 5.6 · ♀ 93% (drug 58%) | no trial data cached |
| Akathisia (inner restlessness) | 29 | 7.3 5.1–10.5ROR 7.3 · χ² 152 / p 4e-35 | 6.7 EB05 4.8 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 6.7 | no trial data cached |
| Adrenal insufficiency | 25 | 7.2 4.9–10.6ROR 7.2 · χ² 127 / p 9e-30 | 6.5 EB05 4.6 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 5.6 · 92% clinician | no trial data cached |
| Red blood cell sedimentation rate increased | 23 | 7.1 4.7–10.7ROR 7.2 · χ² 115 / p 3e-27 | 6.4 EB05 4.4 · IC025 +2.0 3/3 methods agree | Lab value / disease marker | serious PRR 6.3 · 100% clinician | no trial data cached |
| Ventricular fibrillation | 23 | 7.1 4.7–10.7ROR 7.1 · χ² 115 / p 5e-27 | 6.3 EB05 4.4 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 5.5 · 100% clinician | no trial data cached |
| Sedation | 53 | 7.0 5.4–9.2ROR 7.1 · χ² 266 / p 3e-60 | 6.6 EB05 5.3 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 6.1 | no trial data cached |
| Blood pressure fluctuation | 47 | 6.7 5.1–8.9ROR 6.8 · χ² 223 / p 9e-51 | 6.3 EB05 4.9 · IC025 +2.2 3/3 methods agree | Lab value / disease marker | serious PRR 6.3 · ♀ 87% (drug 58%) | no trial data cached |
| Intentional self-injury | 39 | 6.7 4.9–9.1ROR 6.7 · χ² 182 / p 1e-41 | 6.2 EB05 4.7 · IC025 +2.1 3/3 methods agree | Reporting / coding artifact | serious PRR 5.2 · ♀ 88% (drug 58%) | no trial data cached |
| Coordination abnormal | 27 | 6.6 4.5–9.6ROR 6.6 · χ² 123 / p 7e-29 | 6.0 EB05 4.3 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 6.9 · ♀ 82% (drug 58%) | no trial data cached |
| Bipolar disorder | 21 | 6.6 4.3–10.1ROR 6.6 · χ² 94 / p 1e-22 | 5.8 EB05 4.0 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 5.3 | no trial data cached |
| End stage renal disease | 35 | 6.5 4.7–9.1ROR 6.6 · χ² 159 / p 1e-36 | 6.1 EB05 4.5 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Tardive dyskinesia (persistent involuntary movements) | 54 | 6.5 5.0–8.5ROR 6.6 · χ² 247 / p 6e-56 | 6.2 EB05 4.9 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 4.9 | no trial data cached |
| Posterior reversible encephalopathy syndrome | 18 | 6.5 4.1–10.3ROR 6.5 · χ² 78 / p 4e-19 | 5.7 EB05 3.8 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 | no trial data cached |
| Intentional overdose | 120 | 6.5 5.4–7.7ROR 6.6 · χ² 552 / p 3e-122 | 6.3 EB05 5.4 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 5.2 · ♀ 87% (drug 58%) | no trial data cached |
| Chronic kidney disease | 144 | 6.5 5.5–7.6ROR 6.6 · χ² 662 / p 3e-146 | 6.3 EB05 5.5 · IC025 +2.4 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.1 | no trial data cached |
| Cardio-respiratory arrest | 78 | 6.4 5.1–8.0ROR 6.5 · χ² 349 / p 4e-78 | 6.2 EB05 5.1 · IC025 +2.2 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 5.0 | no trial data cached |
| Aspiration | 20 | 6.4 4.1–9.8ROR 6.4 · χ² 85 / p 2e-20 | 5.6 EB05 3.8 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Parkinsonism | 18 | 6.4 4.0–10.1ROR 6.4 · χ² 76 / p 2e-18 | 5.5 EB05 3.7 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 5.4 | no trial data cached |
| Blood urea increased | 30 | 6.1 4.3–8.8ROR 6.2 · χ² 124 / p 5e-29 | 5.6 EB05 4.1 · IC025 +1.9 3/3 methods agree | Lab value / disease marker | serious PRR 5.3 · 100% clinician | no trial data cached |
| Hallucination, auditory | 28 | 6.1 4.2–8.8ROR 6.1 · χ² 113 / p 1e-26 | 5.5 EB05 4.0 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 3.7 | no trial data cached |
| Circulatory collapse | 30 | 6.0 4.2–8.6ROR 6.1 · χ² 121 / p 2e-28 | 5.6 EB05 4.1 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.7 · ♀ 100% (drug 58%) · 100% clinician | no trial data cached |
| Economic problem | 27 | 6.0 4.1–8.8ROR 6.1 · χ² 108 / p 1e-25 | 5.5 EB05 4.0 · IC025 +1.8 3/3 methods agree | Reporting / coding artifact | serious PRR 4.9 · ♀ 32% (drug 58%) | no trial data cached |
| Mydriasis | 22 | 5.9 3.9–9.0ROR 5.9 · χ² 85 / p 2e-20 | 5.3 EB05 3.7 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 5.9 · ♀ 86% (drug 58%) | no trial data cached |
| Metabolic acidosis | 53 | 5.8 4.4–7.5ROR 5.8 · χ² 204 / p 1e-46 | 5.5 EB05 4.4 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 · 100% clinician | no trial data cached |
Trial evidence (ClinicalTrials.gov)
Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Dizziness | 274 | 1.9 1.7–2.1ROR 1.9 · χ² 117 / p 1e-27 | 1.9 EB05 1.7 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.8 | no trial data cached |
| Anxiety | 268 | 3.2 2.9–3.6ROR 3.3 · χ² 416 / p 9e-93 | 3.2 EB05 2.9 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 2.9 | no trial data cached |
| Vomiting | 265 | 1.9 1.7–2.2ROR 2.0 · χ² 123 / p 6e-29 | 1.9 EB05 1.8 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 1.8 | no trial data cached |
| Depression | 245 | 3.7 3.3–4.2ROR 3.8 · χ² 482 / p 3e-107 | 3.7 EB05 3.3 · IC025 +1.7 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.4 | no trial data cached |
| Drug interaction | 237 | 5.1 4.5–5.8ROR 5.3 · χ² 791 / p 2e-174 | 5.1 EB05 4.6 · IC025 +2.1 3/3 methods agree | Reporting / coding artifact | serious PRR 4.3 · ♀ 32% (drug 58%) | no trial data cached |
| Suicidal ideation (thoughts of suicide) | 228 | 8.6 7.5–9.7ROR 8.9 · χ² 1,520 / p <1e-300 | 8.5 EB05 7.6 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 6.6 | no trial data cached |
| Toxicity to various agents | 222 | 4.6 4.0–5.2ROR 4.7 · χ² 616 / p 3e-136 | 4.5 EB05 4.0 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 3.6 · 95% clinician | no trial data cached |
| Fall | 221 | 2.3 2.0–2.6ROR 2.3 · χ² 161 / p 3e-37 | 2.3 EB05 2.0 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 1.9 | no trial data cached |
| Hypotension (low blood pressure) | 219 | 3.8 3.3–4.3ROR 3.9 · χ² 445 / p 4e-99 | 3.7 EB05 3.3 · IC025 +1.7 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.2 | no trial data cached |
| Completed suicide (death by suicide) | 205 | 8.4 7.3–9.6ROR 8.7 · χ² 1,330 / p 2e-291 | 8.3 EB05 7.4 · IC025 +2.8 3/3 methods agree | Outcome field, not a reaction | serious PRR 6.5 · 95% clinician | no trial data cached |
| Acute kidney injury (sudden kidney damage) | 165 | 3.7 3.2–4.3ROR 3.8 · χ² 329 / p 1e-73 | 3.7 EB05 3.2 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 2.9 | no trial data cached |
| Hypertension (high blood pressure) | 156 | 2.5 2.2–3.0ROR 2.6 · χ² 144 / p 2e-33 | 2.5 EB05 2.2 · IC025 +1.1 3/3 methods agree | Likely indication confounding term in indications | serious PRR 2.2 | no trial data cached |
| Insomnia (trouble sleeping) | 150 | 1.9 1.7–2.3ROR 2.0 · χ² 68 / p 1e-16 | 1.9 EB05 1.7 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 2.0 | no trial data cached |
| Feeling abnormal | 144 | 2.1 1.8–2.4ROR 2.1 · χ² 78 / p 5e-19 | 2.1 EB05 1.8 · IC025 +0.8 | Not in label — unassessed | serious PRR 2.1 | no trial data cached |
| Chronic kidney disease | 144 | 6.5 5.5–7.6ROR 6.6 · χ² 662 / p 3e-146 | 6.3 EB05 5.5 · IC025 +2.4 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.1 | no trial data cached |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Sinus bradycardia — n=47, PRR 16.8
- Serotonin syndrome — n=72, PRR 13.0
- Impaired gastric emptying — n=46, PRR 12.4
- Vitamin d deficiency — n=30, PRR 10.6
- Brain injury — n=30, PRR 10.3
- Spinal disorder — n=27, PRR 9.8
- Pulmonary congestion — n=36, PRR 9.4
- Nightmare — n=92, PRR 9.1
- Electrocardiogram qt prolonged — n=94, PRR 9.0
- Suicidal ideation — n=228, PRR 8.6
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Prazosin?
In FDA FAERS, the most frequently co-reported reaction terms for Prazosin are dizziness, anxiety, vomiting, depression, suicidal ideation, toxicity to various agents. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Prazosin have an FDA boxed warning?
No. The FDA label retrieved for Prazosin has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Prazosin causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID 94021822-60cb-4da6-b809-f565e1d6452d, effective 20230915; matched on
openfda.generic_name.exact:"PRAZOSIN") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 502 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.