hydralazine

Absorption: Rapidly absorbed following oral administration; well absorbed from IM sites. IV administration results in complete bioavailability.

Distribution: Widely distributed.

Metabolism/Excretion: Mostly metabolized by the GI mucosa and liver by N-acetyltransferase (rate of acetylation is genetically determined [slow acetylators have ↑ hydralazine levels and ↑ risk of toxicity; fast acetylators have ↓ hydralazine levels and ↓ response]).

Half-Life: 2–8 hr.

Time/Action Profile ⬆ ⬇

(antihypertensive effect)

ROUTE	ONSET	PEAK	DURATION
PO	45 min	2 hr	2–4 hr
IM	10–30 min	1 hr	3–8 hr
IV	5–20 min	15–30 min	2–6 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Some products contain tartrazine and should be avoided in patients with known intolerance.

Use Cautiously in:

Cardiovascular or cerebrovascular disease;
Severe renal impairment (dose modification may be necessary);
Severe hepatic impairment (dose modification may be necessary).

Adv. Reactions/Side Effects ⬆ ⬇

CV: tachycardia, angina, arrhythmias, edema, orthostatic hypotension

Derm: rash

GI: diarrhea, nausea, vomiting

MS: arthralgias, arthritis

Neuro: dizziness, drowsiness, headache, peripheral neuropathy

Misc: drug-induced lupus syndrome

Interactions ⬆ ⬇

Drug-drug:

↑hypotension with acute ingestion of alcohol, other antihypertensives, or nitrates.
MAO inhibitors may exaggerate hypotension.
May ↓ pressor response to epinephrine.
NSAIDs may ↓ antihypertensive response.
Beta blockers↓ tachycardia from hydralazine (therapy may be combined for this reason).
Metoprolol and propranolol↑ levels.
↑levels of metoprolol and propranolol.

Route/Dosage ⬆ ⬇

PO (Adults ): Hypertension: 10 mg 4 times daily initially. After 2–4 days may ↑ to 25 mg 4 times daily for the rest of the 1st wk; may then ↑ to 50 mg 4 times daily (up to 300 mg/day). Once maintenance dose is established, twice-daily dosing may be used. HF: 25–37.5 mg 4 times daily; may be ↑ up to 300 mg/day in 3–4 divided doses.
PO (Children >1 mo): 0.75–1 mg/kg/day in 2–4 divided doses (max = 25 mg/dose) initially; may ↑ gradually to 5 mg/kg/day in infants and 7.5 mg/kg/day in children (max = 200 mg/day) in 2–4 divided doses.
IM IV (Adults ): Hypertension: 5–40 mg repeated as needed. Eclampsia: 5 mg every 15–20 min; if no response after a total of 20 mg, consider an alternative agent.
IM IV (Children >1 mo): 0.1–0.2 mg/kg/dose every 4–6 hr (max = 20 mg/dose) as needed, up to 1.7–3.5 mg/kg/day in 4–6 divided doses.

Availability ⬆ ⬇

(Generic available)

Tablets: 10 mg; 25 mg; 50 mg; 100 mg
Injection: 20 mg/mL
In combination with: isosorbide dinitrate (BiDil). See Appendix [not included in this PDA edition].

Assessment ⬆ ⬇

Monitor BP and pulse frequently during initial dose adjustment and periodically during therapy. About 50–65% of Caucasians, Black, South Indians, and Mexicans are slow acetylators at risk for toxicity, while 80–90% of Inuit, Japanese, and Chinese are rapid acetylators at risk for decreased levels and treatment failure.
- Monitor frequency of prescription refills to determine adherence.

Lab Test Considerations:

Monitor CBC, electrolytes, LE cell prep, and ANA titer prior to and periodically during prolonged therapy.
- May cause a positive direct Coombs’ test result.

Implementation ⬆ ⬇

Do not confuse hydralazine with hydroxyzine, hydromorphone, or hydrochlorothiazide.
- IM or IV route should be used only when drug cannot be given orally.
- May be administered concurrently with diuretics or beta blockers to permit lower doses and minimize side effects.
PO: Administer with meals consistently to enhance absorption.
- Pharmacist may prepare oral solution from hydralazine injection for patients with difficulty swallowing.

IV Administration:

Diluent: Administer undiluted. Use solution as quickly as possible after drawing through needle into syringe.Concentration: 20 mg/mL.
Rate: Administer over at least 1 min. Pedi: Administer at a rate of 0.2 mg/kg/min in children. Monitor BP and pulse in all patients frequently after injection.

Patient/Family Teaching ⬆ ⬇

Emphasize the importance of continuing to take this medication, even if feeling well. Instruct patient to take medication at the same time each day; last dose of the day should be taken at bedtime. Take missed doses as soon as remembered; do not double doses. If more than 2 doses in a row are missed, consult health care professional. Must be discontinued gradually to avoid sudden increase in BP. Hydralazine controls but does not cure hypertension.
Encourage patient to comply with additional interventions for hypertension (weight reduction, low-sodium diet, smoking cessation, moderation of alcohol intake, regular exercise, and stress management). Instruct patient and family on proper technique for BP monitoring. Advise them to check BP at least weekly and report significant changes.
Patients should weigh themselves twice weekly and assess feet and ankles for fluid retention.
May occasionally cause drowsiness. Advise patient to avoid driving or other activities requiring alertness until response to medication is known.
Caution patient to avoid sudden changes in position to minimize orthostatic hypotension.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications, especially cough, cold, or allergy remedies.
Instruct patient to notify health care professional of medication prior to treatment or surgery.
Advise patient to notify health care professional immediately if general tiredness; fever; muscle or joint aching; chest pain; skin rash; sore throat; or numbness, tingling, pain, or weakness of hands and feet occurs. Vitamin B₆ (pyridoxine) may be used to treat peripheral neuritis.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
Emphasize the importance of follow-up exams to evaluate effectiveness of medication.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇