Hydralazine

Severe essential hypertension when the drug cannot be given orally or when there is an urgent need to lower blood pressure.

of hydralazine is not fully understood, the major effects are on the cardiovascular system. Hydralazine apparently lowers blood pressure by exerting a peripheral vasodilating effect through a direct relaxation of vascular smooth muscle. Hydralazine, by altering cellular calcium metabolism, interferes with the calcium movements within the vascular smooth muscle that are responsible for initiating or maintaining the contractile state. The peripheral vasodilating effect of hydralazine results in decreased arterial blood pressure (diastolic more than systolic), decreased peripheral vascular resistance, and an increased heart rate, stroke volume and cardiac output. The preferential dilatation of arterioles, as compared to veins, minimizes postural hypotension and promotes the increase in cardiac output.

When there is urgent need, therapy in the hospitalized patient may be initiated intramuscularly or as a rapid intravenous bolus injection directly into the vein. Hydralazine Hydrochloride Injection should be used only when the drug cannot be given orally. The usual dose is 20 to 40 mg, repeated as necessary. Certain patients (especially those with marked renal damage) may require a lower dose. Blood pressure should be checked frequently. It may begin to fall within a few minutes after injection, with the average maximal decrease occurring in 10 to 80 minutes. In cases where there has been increased intracranial pressure, lowering the blood pressure may increase cerebral ischemia. Most patients can be transferred to oral hydralazine hydrochloride within 24 to 48 hours. The product should be used immediately after the vial is opened. The product should not be added to infusion solutions.

Hypersensitivity to hydralazine, coronary artery disease, mitral valvular rheumatic heart disease.

In a few patients, hydralazine may produce a clinical picture simulating systemic lupus erythematosus including glomerulonephritis. In such patients, hydralazine should be discontinued unless the benefit-to-risk determination requires continued antihypertensive therapy with this drug. Symptoms and signs usually regress when the drug is discontinued but residua have been detected many years later. Long-term treatment with steroids may be necessary.

Adverse reactions with hydralazine hydrochloride are usually reversible when dosage is reduced. However, in some cases it may be necessary to discontinue the drug. The following adverse reactions have been observed, but there has not been enough systematic collection of data to support an estimate of their frequency. 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.

Store at 20° to 25°C (68° to 77°F).