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Pharmacologic class: Beta-adrenergic blocker (nonselective), alpha-adrenergic blocker (selective)
Therapeutic class: Antihypertensive
Pregnancy risk category C
Blocks stimulation of beta1- and beta2-adrenergic receptor sites and alpha1-adrenergic receptors, decreasing myocardial contractile force and enhancing coronary artery blood flow and myocardial perfusion. Net effect is decreased heart rate and blood pressure.
Injection: 5 mg/ml
Tablets: 100 mg, 200 mg, 300 mg
Indications and dosages
Adults: Initially, 100 mg P.O. b.i.d., alone or combined with a diuretic; may increase by 100 mg b.i.d. q 2 to 3 days as needed. Usual range is 400 to 800 mg/day in two divided doses; up to 2.4 g/day have been given.
➣ Hypertensive crisis
Adults: Initially, 20 mg I.V. bolus over 2 minutes, then I.V. injection of 40 to 80 mg q 10 minutes until blood pressure falls to desired level; maximum dosage is 300 mg. Alternatively, 50 to 200 mg by continuous I.V. infusion at 2 mg/minute; continue infusion until desired blood pressure is reached. Follow I.V. dosing with P.O. dosing.
➣ Conversion from I.V. to P.O. dosing
Hospitalized adults: Discontinue I.V. therapy when desired blood pressure is reached; start P.O. dosing when supine diastolic pressure begins to rise. Initial P.O. dosage is 200 mg, followed 6 to 12 hours later with additional dose of 200 to 400 mg P.O., depending on blood pressure response. Then titrate at 1-day intervals to dosage ranging from 400 to 2,400 mg/day P.O. in two or three divided doses.
• Chronic hepatic disease
• Elderly patients
• Hypertension secondary to pheochromocytoma or clonidine withdrawal
• Hypersensitivity to drug
• Bronchospastic disease
• Overt heart failure, cardiogenic shock
• Second- or third-degree atrioventricular block
• Severe bradycardia
• Conditions associated with severe and prolonged hypotension
Use cautiously in:
• hepatic impairment, pulmonary disease, diabetes mellitus, hyperthyroidism, thyrotoxicosis
• elderly patients
• pregnant or breastfeeding patients
• Know that drug may be given as I.V. bolus or continuous infusion.
• Be aware that drug may be given undiluted for I.V. bolus injection. For continuous infusion, dilute in dextrose 5% in water or normal saline solution, and deliver with infusion control pump.
• Don't mix with 5% sodium bicarbonate injection.
• Give direct I.V. injection over 2 minutes at 10-minute intervals.
CNS: fatigue, asthenia, anxiety, depression, dizziness, paresthesia, drowsiness, insomnia, memory loss, nightmares, mental status changes
CV: orthostatic hypotension, peripheral vasoconstriction, bradycardia, arrhythmias, heart failure
EENT: blurred vision, dry eyes, nasal congestion
GI: nausea, diarrhea, constipation
GU: erectile dysfunction, decreased libido
Hematologic: purpura, agranulocytosis, thrombocytopenia
Metabolic: hyperglycemia, hypoglycemia
Musculoskeletal: joint pain, back pain, muscle cramps
Respiratory: wheezing, bronchospasm, pulmonary edema
Skin: rash, pruritus
Drug-drug. Adrenergic bronchodilators, theophylline: decreased efficacy of these drugs
Antihypertensives, nitrates: additive hypotension
Cimetidine, propranolol: increased labetalol effects
Digoxin: additive bradycardia
Dobutamine, dopamine: reduced beneficial cardiovascular effects of these drugs
General anesthetics, verapamil: additive myocardial depression
Insulin, oral hypoglycemics: altered hypoglycemic efficacy
MAO inhibitors: hypertension
Nonsteroidal anti-inflammatory drugs: decreased antihypertensive action
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, antinuclear antibodies, aspartate aminotransferase, blood urea nitrogen, glucose, liver function tests, low-density lipoproteins, potassium, triglycerides, uric acid: increased values
• Monitor ECG and vital signs, especially blood pressure.
• Assess cardiovascular, respiratory, and neurologic status closely to detect adverse reactions.
• Monitor CBC, blood glucose level, and liver function tests.
☞ Instruct patient to immediately report adverse reactions, such as easy bruising or bleeding or respiratory problems.
• Tell patient he may feel dizzy when starting therapy, especially if he's also taking a diuretic.
• Advise patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, and alertness.
• Emphasize need for follow-up care and regular blood pressure monitoring.
☞ Caution patient not to stop taking drug abruptly, because this may cause myocardial infarction or worsen angina.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.