Prazosin Hydrochloride side effects: what 1,308 FDA adverse event reports show
Drug class
Not stated in label
Who reports
1,308 reports · 63% serious · 90 with death outcome · 63% female
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.
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:
Boxed warning
None in the current label
Causality screen of the 22 strongest signals
What the badges mean
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- 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. 28 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Gout | 36 | 32.2 23.3–44.4ROR 33.1 · χ² 1,056 / p 7e-232 | 31.6 EB05 23.9 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious PRR 43.1 · ♀ 97% (drug 63%) | no trial data cached |
| Neutrophil count increased | 16 | 25.0 15.4–40.7ROR 25.3 · χ² 345 / p 3e-77 | 24.3 EB05 15.8 · IC025 +3.0 3/3 methods agree | Lab value / disease marker | serious PRR 25.1 | no trial data cached |
| Haematuria (blood in urine) | 51 | 23.9 18.2–31.2ROR 24.8 · χ² 1,095 / p 2e-240 | 23.7 EB05 18.7 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 24.0 · ♀ 100% (drug 63%) | no trial data cached |
| Hyperkalaemia (high potassium) | 47 | 21.6 16.3–28.6ROR 22.4 · χ² 904 / p 7e-199 | 21.4 EB05 16.7 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious PRR 20.2 | no trial data cached |
| Blood urea increased | 18 | 17.2 10.8–27.2ROR 17.4 · χ² 258 / p 2e-58 | 16.6 EB05 10.7 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 17.4 | no trial data cached |
| Infusion site pain | 12 | 15.1 8.6–26.5ROR 15.2 · χ² 144 / p 2e-33 | 13.8 EB05 7.5 · IC025 +2.3 3/3 methods agree | Labeled (related wording) related wording | serious n=11 | no trial data cached |
| Blood alkaline phosphatase increased | 23 | 14.8 9.9–22.2ROR 15.1 · χ² 283 / p 8e-64 | 14.4 EB05 9.7 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 15.6 · 100% clinician | no trial data cached |
| Impaired quality of life | 13 | 14.5 8.4–24.9ROR 14.6 · χ² 150 / p 8e-35 | 13.3 EB05 7.4 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Insurance issue | 12 | 13.0 7.4–22.8ROR 13.1 · χ² 121 / p 2e-28 | 11.4 EB05 6.2 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 24.4 | no trial data cached |
| Premature delivery | 12 | 12.0 6.8–21.1ROR 12.1 · χ² 111 / p 4e-26 | 10.4 EB05 5.7 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 11.3 | no trial data cached |
| Renal impairment | 62 | 11.9 9.3–15.2ROR 12.4 · χ² 609 / p 8e-135 | 11.7 EB05 9.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 11.3 · ♀ 96% (drug 63%) | no trial data cached |
| Sinus tachycardia | 10 | 11.3 6.1–21.0ROR 11.4 · χ² 84 / p 2e-20 | 9.2 EB05 4.8 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 10.6 | no trial data cached |
| Product dose omission in error | 17 | 10.2 6.3–16.3ROR 10.3 · χ² 131 / p 1e-30 | 8.9 EB05 5.6 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | serious PRR 8.6 | no trial data cached |
| Premature baby | 15 | 8.0 4.8–13.2ROR 8.0 · χ² 85 / p 2e-20 | 6.7 EB05 4.2 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 7.4 | no trial data cached |
| Blood pressure fluctuation | 11 | 7.3 4.1–13.2ROR 7.4 · χ² 54 / p 1e-13 | 5.9 EB05 3.4 · IC025 +1.5 3/3 methods agree | Lab value / disease marker | serious PRR 6.9 | no trial data cached |
| Respiratory arrest | 12 | 6.9 3.9–12.2ROR 7.0 · χ² 55 / p 6e-14 | 5.6 EB05 3.4 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 6.3 | no trial data cached |
| Product dose omission issue | 103 | 5.8 4.8–7.0ROR 6.2 · χ² 410 / p 2e-91 | 5.7 EB05 4.8 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | serious PRR 9.3 · 75% consumer | no trial data cached |
| Completed suicide (death by suicide) | 30 | 5.7 4.0–8.1ROR 5.8 · χ² 113 / p 1e-26 | 5.3 EB05 3.9 · IC025 +1.8 3/3 methods agree | Outcome field, not a reaction | serious PRR 5.2 · 100% clinician | no trial data cached |
| Suicidal ideation (thoughts of suicide) | 25 | 4.4 3.0–6.4ROR 4.4 · χ² 62 / p 2e-15 | 4.1 EB05 2.9 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.1 | no trial data cached |
| Maternal exposure during pregnancy | 24 | 4.4 2.9–6.5ROR 4.4 · χ² 59 / p 7e-15 | 4.1 EB05 2.9 · IC025 +1.3 3/3 methods agree | Reporting / coding artifact | serious PRR 4.9 · ♀ 100% (drug 63%) | no trial data cached |
| Dermatitis atopic | 11 | 3.5 2.0–6.4ROR 3.6 · χ² 18 / p 1e-5 | 3.2 EB05 1.9 · IC025 +0.6 | Not in label — unassessed | serious n=2 | no trial data cached |
| Intentional overdose | 10 | 2.5 1.4–4.7ROR 2.5 · χ² 8 / p 0.003 | 2.3 EB05 1.4 · IC025 +0.2 | Reporting / coding artifact | serious PRR 2.1 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
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 |
|---|---|---|---|---|---|---|
| Product dose omission issue | 103 | 5.8 4.8–7.0ROR 6.2 · χ² 410 / p 2e-91 | 5.7 EB05 4.8 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | serious PRR 9.3 · 75% consumer | no trial data cached |
| Renal impairment | 62 | 11.9 9.3–15.2ROR 12.4 · χ² 609 / p 8e-135 | 11.7 EB05 9.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 11.3 · ♀ 96% (drug 63%) | no trial data cached |
| Haematuria (blood in urine) | 51 | 23.9 18.2–31.2ROR 24.8 · χ² 1,095 / p 2e-240 | 23.7 EB05 18.7 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 24.0 · ♀ 100% (drug 63%) | no trial data cached |
| Hyperkalaemia (high potassium) | 47 | 21.6 16.3–28.6ROR 22.4 · χ² 904 / p 7e-199 | 21.4 EB05 16.7 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious PRR 20.2 | no trial data cached |
| Gout | 36 | 32.2 23.3–44.4ROR 33.1 · χ² 1,056 / p 7e-232 | 31.6 EB05 23.9 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious PRR 43.1 · ♀ 97% (drug 63%) | no trial data cached |
| Completed suicide (death by suicide) | 30 | 5.7 4.0–8.1ROR 5.8 · χ² 113 / p 1e-26 | 5.3 EB05 3.9 · IC025 +1.8 3/3 methods agree | Outcome field, not a reaction | serious PRR 5.2 · 100% clinician | no trial data cached |
| Suicidal ideation (thoughts of suicide) | 25 | 4.4 3.0–6.4ROR 4.4 · χ² 62 / p 2e-15 | 4.1 EB05 2.9 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.1 | no trial data cached |
| Maternal exposure during pregnancy | 24 | 4.4 2.9–6.5ROR 4.4 · χ² 59 / p 7e-15 | 4.1 EB05 2.9 · IC025 +1.3 3/3 methods agree | Reporting / coding artifact | serious PRR 4.9 · ♀ 100% (drug 63%) | no trial data cached |
| Blood alkaline phosphatase increased | 23 | 14.8 9.9–22.2ROR 15.1 · χ² 283 / p 8e-64 | 14.4 EB05 9.7 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 15.6 · 100% clinician | no trial data cached |
| Blood urea increased | 18 | 17.2 10.8–27.2ROR 17.4 · χ² 258 / p 2e-58 | 16.6 EB05 10.7 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 17.4 | no trial data cached |
| Product dose omission in error | 17 | 10.2 6.3–16.3ROR 10.3 · χ² 131 / p 1e-30 | 8.9 EB05 5.6 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | serious PRR 8.6 | no trial data cached |
| Neutrophil count increased | 16 | 25.0 15.4–40.7ROR 25.3 · χ² 345 / p 3e-77 | 24.3 EB05 15.8 · IC025 +3.0 3/3 methods agree | Lab value / disease marker | serious PRR 25.1 | no trial data cached |
| Premature baby | 15 | 8.0 4.8–13.2ROR 8.0 · χ² 85 / p 2e-20 | 6.7 EB05 4.2 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 7.4 | no trial data cached |
| Impaired quality of life | 13 | 14.5 8.4–24.9ROR 14.6 · χ² 150 / p 8e-35 | 13.3 EB05 7.4 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Respiratory arrest | 12 | 6.9 3.9–12.2ROR 7.0 · χ² 55 / p 6e-14 | 5.6 EB05 3.4 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 6.3 | 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.
- Gout — n=36, PRR 32.2
- Haematuria — n=51, PRR 23.9
- Hyperkalaemia — n=47, PRR 21.6
- Renal impairment — n=62, PRR 11.9
- Suicidal ideation — n=25, PRR 4.4
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 renal impairment, haematuria, hyperkalaemia, gout, suicidal ideation, blood alkaline phosphatase increased. 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, 50 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.