hydralazine hydrochloride

Action

Relaxes vascular smooth muscles of arteries and arterioles, causing peripheral vasodilation and decreasing peripheral vascular resistance. These actions decrease blood pressure and increase heart rate, stroke volume, and cardiac output.

Availability

Injection: 20 mg/ml

Tablets: 10 mg, 25 mg, 50 mg, 100 mg

Indications and dosages

➣ Hypertension

Adults: Initially, 10 mg P.O. q.i.d. After 2 to 4 days, may increase to 25 mg P.O. q.i.d. for remainder of first week; may then increase further to 50 mg P.O. q.i.d., up to 300 mg/day. Once maintenance dosage is established, may give in two daily doses.

Children: Initially, 0.75 mg/kg/day P.O. in four divided doses; may increase gradually over 3 to 4 weeks to 7.5 mg/kg or 200 mg/day

Neonates: 0.5 mg/kg P.O., I.M., or I.V. q 4 to 6 hours

Contraindications

• Hypersensitivity to drug or tartrazine

• Coronary artery disease

• Mitral valvular rheumatic heart disease

Precautions

Use cautiously in:

• suspected CV or cerebrovascular disease, severe renal or hepatic disease

• pregnant or breastfeeding patients

• children.

Administration

• Administer oral form with food.

See Inject I.V. form slowly over 1 minute. Monitor blood pressure response continuously.

• Draw up and use parenteral drug immediately; solution changes color after contact with metal needle.

Adverse reactions

CNS: dizziness, drowsiness, headache, peripheral neuritis

CV: tachycardia, angina, orthostatic hypotension, arrhythmias

EENT: lacrimation, nasal congestion

GI: nausea, vomiting, diarrhea, constipation, anorexia

Metabolic: sodium retention

Musculoskeletal: joint pain, arthritis

Skin: rash, blisters, flushing, pruritus, urticaria

Other: chills, fever, lymphadenopathy, edema, lupuslike syndrome

Interactions

Drug-drug. Antihypertensives, nitrates: additive hypotension

Epinephrine: reduced pressor response to epinephrine

Metoprolol, propranolol: increased blood levels of both drugs

MAO inhibitors: increased hypotension

Drug-diagnostic tests. Coombs' test: positive result

Granulocytes, hemoglobin, neutrophils, platelets, red blood cells, white blood cells: decreased levels

Drug-behaviors. Alcohol use: additive hypotensive response

Patient monitoring

• Monitor CBC, lupus erythematosus cell studies, and antinuclear antibody titers before and periodically during therapy.

• Monitor blood pressure, pulse rate and regularity, and daily weight.

• To avoid rapid blood pressure drop, taper dosage gradually before discontinuing.

See Assess for lupuslike signs and symptoms, including joint pain, fever, myalgia, pharyngitis, and splenomegaly.

• Watch for peripheral neuritis. If it occurs, expect to give pyridoxine.

Patient teaching

• Tell patient to take tablets with food.

• Instruct patient to move slowly when rising (especially in morning on awakening), to avoid dizziness from sudden blood pressure decrease.

See Instruct patient to immediately report fever, muscle and joint aches, or sore throat.

• Tell patient to report chest pain or numbness or tingling of hands or feet.

• To minimize GI upset, advise patient to eat small, frequent meals.

• Caution patient not to discontinue drug abruptly, because severe hypertension may result.

• As appropriate, review other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.