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Source overview
Recorded excerpts for one species. Each dose remains a separate source entry; no regimen is selected.
Choose one species to view its source overview. All-species evidence remains available below.
View full clinical evidence and sources ↓Clinical evidence
Pending clinical review (PROPOSED)Rule-based (RULE_BASED)— applies to the facts and dose entries in this species selection; individual source records retain their own status.
Indications2
Afterload reducer in CHF (esp. mitral valve insufficiency when ACE inhibitors insufficient; severe aortic regurgitation, large septal defects); systemic hypertension
DogExtra-label (EXTRA_LABEL)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Afterload reducer in CHF (esp. mitral valve insufficiency when ACE inhibitors insufficient; severe aortic regurgitation, large septal defects); systemic hypertension — Extra-label (human drug)
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Same — adjunctive CHF/hypertension
CatExtra-label (EXTRA_LABEL)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Same — adjunctive CHF/hypertension — Extra-label
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Indications table · Not applicable · Extra-label (EXTRA_LABEL) · Pending clinical review (PROPOSED) · Rule-based
Dose regimens4
This calculator performs arithmetic only on the sourced dosing field shown for each result — it does not verify the field's accuracy, does not select which field to use for a patient, and does not replace a veterinarian's order. Not for clinical use. Confirm every result against the primary source before dispensing.
Choose one species above to view its dose calculator.
Adverse effects33
Hypotension, weakness, syncope — Most prevalent — especially with rapid up-titration
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Reflex tachycardia — Expected; treat with digoxin or beta-blocker (caution: β-blockers ↓ cardiac performance)
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Sodium/water retention (RAAS activation) — If not paired with diuretic; can ↑ creatinine
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Vomiting/diarrhea — GI distress
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
SLE-like syndrome, blood dyscrasias, peripheral neuritis — Human-documented; caution with autoimmune disease
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
These are counts of spontaneously reported events, not proven adverse effects, causal relationships, or incidence rates.
Bars compare report counts within each species; they do not show incidence.
More reportsFewer reportsDog
- Diarrhoea2 reports
- Elevated blood urea nitrogen (BUN)2 reports
- Elevated creatinine2 reports
- Elevated symmetrical dimethylarginine (SDMA)2 reports
- Abnormal adrenocorticotropic hormone (ACTH) stimulation test1 reports
- Abnormal ultrasound finding1 reports
- Acute renal failure1 reports
- Adrenal gland disorder NOS1 reports
- Biting -aggression (see also Skin and appendages disorders)1 reports
- Death1 reports
- Decreased appetite1 reports
- Drug name look-alike1 reports
Monitoring1
Blood pressure (MAP target 60–80 mmHg); mucous membrane color/CRT, murmur intensity, radiographs (pulmonary edema); renal values/creatinine; heart rate
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Monitoring Parameters · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Contraindications1
Hypersensitivity; coronary artery disease; hypovolemia or preexisting hypotension
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Precautions5
Renal disease (RAAS activation + reduced renal flow — pre-treat with ACE inhibitor ± spironolactone); intracerebral bleeding; preexisting autoimmune disease; not useful when primary myocardial disease present
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Titrate slowly — severe hypotension is the classic hydralazine error. When BP monitoring is unavailable, titrate on clinical + radiographic signs over 12–48 h steps.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Always pair with a diuretic in CHF (sodium/water retention otherwise undoes the benefit) and consider pre-treating kidneys with ACEi + spironolactone.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Dogs lack the N-acetylation pathway that humans use to clear hydralazine — narrower safety margin than human pharmacology suggests.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Reserved mostly for mitral-insufficiency CHF unresponsive to ACE inhibitors — not effective for primary myocardial failure.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Interactions4
Diuretics — Usually needed concurrently (offsets retention)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Beta-blockers — Blunt reflex tachycardia (but may reduce cardiac output)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Other hypotensives/ACE inhibitors — Additive hypotension — careful titration
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Nitroglycerin ointment — Often added to reduce preload alongside afterload reduction
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pharmacokinetics5
Onset/peak — Within 1 h; peak 3–5 h; duration 11–13 h (dog PO)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Bioavailability — High first-pass (saturable — ↑ with dose); food ↓ bioavailability ~63% in dogs
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Protein binding — ~85% (human)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Metabolism — Extensive hepatic; N-acetylation pathway mostly ABSENT in dogs → toxicity concern
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Half-life — 2–4 h (up to 8 h) human data
Other speciesNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Other species · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pregnancy / lactation considerations1
Human FDA category C; canine/feline class B (Papich 1989). Crosses placenta; minute amounts in milk.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 609–610; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 376–377 — Pregnancy & Lactation · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Literature references20
References are linked to this drug. Species applicability is not recorded here, so the species filter does not narrow this list. Imported dates do not retain their original precision; confirm dates in the original citation.
- Hydralazine rescues PC12 cells from acrolein-mediated death.
Study summary not available in the imported record. Open the original citation to review the study.
- [Primary aldosteronism and pregnancy: report of 2 cases].
Study summary not available in the imported record. Open the original citation to review the study.
- Differentiating spontaneous from drug-induced vascular injury in the dog.
Study summary not available in the imported record. Open the original citation to review the study.
- Advancing nonclinical blood pressure assessment: Current practices and future directions in drug development.
Study summary not available in the imported record. Open the original citation to review the study.
- Novel O-methylpyrimidine prodrugs of phenolic compounds bioactivated by aldehyde oxidase: Enhancing metabolic stability against first-pass conjugative metabolism in the intestine.
Study summary not available in the imported record. Open the original citation to review the study.
Sources: PubMed, National Library of Medicine; openFDA, U.S. Food and Drug Administration; Plumb DC. Plumb's Veterinary Drug Handbook. 7th ed. PharmaVet Inc; 2011.
Owner information handout
Plain-language medication information to review with the owner. Open the handout to print it or download a PDF.