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.
Side 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.
Mode 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.