hydrALAZINE (hye-dral-a-zeen) Apresoline

 Indications

Moderate to severe hypertension (with a diuretic). Unlabeled

Use: HF unresponsive to conventional therapy

with digoxin and diuretics.

Action

Direct-acting peripheral arteriolar vasodilator. Therapeutic

Effects: Lowering of BP in hypertensive patients

and decreased afterload in patients with HF. 

Pharmacokinetics

Absorption: Rapidly absorbed following oral administration;

well absorbed from IM sites.

Distribution: Widely distributed. Crosses the placenta;

enters breast milk in minimal concentrations.

Metabolism and Excretion: Mostly metabolized

by the GI mucosa and liver by N-acetyltransferase

(rate of acetylation is genetically determined [slow acetylators

haveqhydralazine levels andqrisk of toxicity;

fast acetylators havephydralazine levels andpresponse]).

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

Contraindications/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 and hepatic impairment

(dose modification may be necessary); OB, Lactation:

Has been used safely during pregnancy.

Adverse Reactions/Side Effects

CNS: dizziness, drowsiness, headache. CV: tachycardia,

angina, arrhythmias, edema, orthostatic hypotension.

GI: diarrhea, nausea, vomiting. Derm: rash.

MS: arthralgias, arthritis. Neuro: peripheral neuropathy.

Misc: drug-induced lupus syndrome.

Interactions

Drug-Drug:qhypotension with acute ingestion of

alcohol, other antihypertensives, or nitrates. MAO

inhibitors may exaggerate hypotension. Mayppressor

response to epinephrine. NSAIDs maypantihypertensive

response. Beta blockersptachycardia

from hydralazine (therapy may be combined for this

reason). Metoprolol and propranololqlevels.q

levels of metoprolol and propranolol.

Route/Dosage

PO (Adults): Hypertension—10 mg 4 times daily initially.

After 2–4 days mayqto 25 mg 4 times daily for

the rest of the 1st week; may thenqto 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 bequp to 300 mg/day in

3–4 divided doses.

PO (Children 1 mo): Initial—0.75–1 mg/kg/day

in 2–4 divided doses, not to exceed 25 mg/dose; may

qgradually to 5 mg/kg/day in infants and 7.5 mg/kg/

day in children (not to exceed 200 mg/day) in 2–4 divided

doses.

IM, IV (Adults): Hypertension—5–40 mg repeated

as needed. Eclampsia—5mg q 15–20min; if no response

after a total of 20 mg, consider an alternative

agent.

IM, IV (Children 1mo): Initial—0.1–0.2 mg/kg/

dose (not to exceed 20 mg) every 4–6 hr 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 B.