Hydralazine

Indications

Hydralazine is used for: Severe Essential Hypertension, Hypertensive Crisis,

Adult Dose

Severe Essential Hypertension 10 mg PO q6hr for 2-4 days; 25 mg q6hr daily for the first week; increase to 50 mg q6hr from second week on; adjust dose to lowest effective levels 20-40 mg IM/IV; repeat as necessary Dosing considerations Change to oral therapy as soon as possible Hypertension (Chronic) Initial: 10 mg PO q6hr for 2-4 days; may increase gradually by 10-25 mg/dose every 2-5 days up to 50 mg PO q6hr (some patients require 300 mg/day) Hypertensive Crisis 20-40 mg IV/IM; repeat PRN Pregnancy-associated 5-10 mg IV/IM initially, THEN 5-10 mg q20-30min PRN, OR 0.5-10 mg/hr IV infusion Congestive Heart Failure Initial dose: 10-25 mg q6-8hr PO Maintenance dose: 225-300 mg/day divided q6-8hr PO

Child Dose

Severe Essential Hypertension 1.7-3.5 mg/kg/day IM or IV divided in 4-6 doses. Hypertensive Crisis 3 months - 1 year: 0.1-0.5 mg/kd/dose IV q6-8hr; not to excced 2 mg/kg IV q6hr; titrate dose for blood pressure control >1 year: 0.1-0.2 mg/kg IV/IM q4-6hr PRN initially; may increase to usual dose of 1.7-3.5 mg/kg/day divided q4-6hr; not to exceed 20 mg/dose IM or IV or 2 mg/kg q3-6hr with cumulative dose not to exceed 9 mg/kg Hypertension (Chronic) Initial: 0.75-1 mg/kg/day PO divided q6-12hr Maximum dose in infants (<1 year): 5 mg/kg/day PO divided q6-12hr, 20 mg/dose, or 200 mg/day Maximum dose in children (>1 year): 7.5 mg/kg/day PO divided q6hr; not to exceed 200 mg/day Increase gradually over 3-4 weeks

Renal Dose

Administration

Should be taken with food.

Contra Indications

Hypersensitivity to hydralazine, Severe tachycardia, dissecting aortic aneurysm, heart failure with high cardiac output, cor pulmonale, myocardial insufficiency due to mechanical obstruction, coronary artery disease, idiopathic SLE. Patients with recent MI.

Precautions

Cerebrovascular disorders. Ischaemic heart disease. Hepatic or renal impairment. May deplete pyridoxine in the body. May impair ability to drive or operate machinery. Monitor for postural hypotension if given to patients with heart failure. Withdraw gradually. CBC and antinuclear antibody tests should be carried out every 6 mth during long-term therapy. Urine analysis is also recommended. Pregnancy and lactation. Daily doses >100 mg may increase the risk of SLE especially in women and slow acetylators. Lactation: Excreted in breast milk; use caution

Pregnancy-Lactation

Pregnancy category: C Lactation: Excreted in breast milk; use caution

Interactions

Hypotensives, diazoxide, NSAIDs, oestrogens, sympathomimetics.

Adverse Effects

Side effects of Hydralazine : Common Headache, anorexia, nausea, vomiting, diarrhea, palpitations, tachycardia, angina pectoris. Less Frequent Digestive: constipation, paralytic ileus. Cardiovascular: hypotension, paradoxical pressor response, edema. Respiratory: dyspnea. Neurologic: peripheral neuritis evidenced by paresthesia, numbness, and tingling, dizziness: tremors; muscle cramps; psychotic reactions characterized by depression, disorientation, or anxiety. Genitourinary: difficulty in urination. Hematologic: blood dyscrasias, consisting of reduction in hemoglobin and red cell count, leukopenia, agranulocytosis, purpura, lymphadenopathy; splenomegaly. Hypersensitive Reactions: rash, urticaria, pruritus, fever, chills, arthralgia, eosinophilia, and, rarely, hepatitis. Other: nasal congestion, flushing, lacrimation, conjunctivitis.

Mechanism of Action

Hydralazine is a direct-acting vasodilator which acts predominantly on the arterioles. It reduces BP and peripheral resistance but produces fluid retention. Hydralazine tends to improve renal and cerebral blood flow and its effect on diastolic pressure is more marked than on systolic pressure.