ADVERSE REACTIONS

Most adverse effects have been mild and transient and have rarely required withdrawal of therapy.

Cardiovascular

Bradycardia with heart rates of less than 60 beats per minute occurs commonly, and heart rates below 40 beats per minute and/or symptomatic bradycardia were seen in about 2 of 100 patients. Symptoms of peripheral vascular insufficiency, usually of the Raynaud type, have occurred in approximately 2 of 100 patients. Cardiac failure, hypotension, and rhythm/conduction disturbances have each occurred in about 1 of 100 patients. Single instances of first degree and third degree heart block have been reported; intensification of AV block is a known effect of beta-blockers (see also CONTRAINDICATIONS**,WARNINGS, andPRECAUTIONS**).

Central Nervous System

Dizziness or fatigue has been reported in approximately 2 of 100 patients; paresthesias, sedation, and change in behavior have each been reported in approximately 6 of 1,000 patients.

Respiratory

Bronchospasm has been reported in approximately 1 of 1,000 patients (see CONTRAINDICATIONSandWARNINGS).

Gastrointestinal

Nausea, diarrhea, abdominal discomfort, constipation, vomiting, indigestion, anorexia, bloating, and flatulence have been reported in 1 to 5 of 1,000 patients.

Miscellaneous

Each of the following has been reported in 1 to 5 of 1,000 patients: rash; pruritus; headache; dry mouth, eyes, or skin; impotence or decreased libido; facial swelling; weight gain; slurred speech; cough; nasal stuffiness; sweating; tinnitus; blurred vision. Reversible alopecia has been reported infrequently.

The following adverse reactions have been reported in patients taking nadolol and/or other beta-adrenergic blocking agents, but no causal relationship to nadolol has been established.

Central Nervous System

Reversible mental depression progressing to catatonia; visual disturbances; hallucinations; an acute reversible syndrome characterized by disorientation for time and place, short-term memory loss, emotional lability with slightly clouded sensorium, and decreased performance on neuropsychometrics.

Gastrointestinal

Mesenteric arterial thrombosis; ischemic colitis; elevated liver enzymes.

Hematologic

Agranulocytosis; thrombocytopenic or nonthrombocytopenic purpura.

Allergic

Fever combined with aching and sore throat; laryngospasm; respiratory distress.

Miscellaneous

Pemphigoid rash; hypertensive reaction in patients with pheochromocytoma; sleep disturbances; Peyronie’s disease. The oculomucocutaneous syndrome associated with the beta-blocker practolol has not been reported with nadolol.

CLINICAL PHARMACOLOGY

Nadolol is a nonselective beta-adrenergic receptor blocking agent. Clinical pharmacology studies have demonstrated beta-blocking activity by showing (1) reduction in heart rate and cardiac output at rest and on exercise, (2) reduction of systolic and diastolic blood pressure at rest and on exercise, (3) inhibition of isoproterenol-induced tachycardia, and (4) reduction of reflex orthostatic tachycardia.

Nadolol specifically competes with beta-adrenergic receptor agonists for available beta receptor sites; it inhibits both the beta 1receptors located chiefly in cardiac muscle and the beta 2receptors located chiefly in the bronchial and vascular musculature, inhibiting the chronotropic, inotropic, and vasodilator responses to beta-adrenergic stimulation proportionately. Nadolol has no intrinsic sympathomimetic activity and, unlike some other beta- adrenergic blocking agents, nadolol has little direct myocardial depressant activity and does not have an anesthetic-like membrane stabilizing action. Animal and human studies show that nadolol slows the sinus rate and depresses AV conduction. In dogs, only minimal amounts of nadolol were detected in the brain relative to amounts in blood and other organs and tissues. Nadolol has low lipophilicity as determined by octanol/ water partition coefficient, a characteristic of certain beta-blocking agents that has been correlated with the limited extent to which these agents cross the blood-brain barrier, their low concentration in the brain, and low incidence of CNS-related side effects.

In controlled clinical studies, nadolol at doses of 40 to 320 mg/day has been shown to decrease both standing and supine blood pressure, the effect persisting for approximately 24 hours after dosing.

The mechanism of the antihypertensive effects of beta-adrenergic receptor blocking agents has not been established; however, factors that may be involved include (1) competitive antagonism of catecholamines at peripheral (non-CNS) adrenergic neuron sites (especially cardiac) leading to decreased cardiac output, (2) a central effect leading to reduced tonic-sympathetic nerve outflow to the periphery, and (3) suppression of renin secretion by blockade of the beta-adrenergic receptors responsible for renin release from the kidneys.

While cardiac output and arterial pressure are reduced by nadolol therapy, renal hemodynamics are stable, with preservation of renal blood flow and glomerular filtration rate.

By blocking catecholamine-induced increases in heart rate, velocity and extent of myocardial contraction, and blood pressure, nadolol generally reduces the oxygen requirements of the heart at any given level of effort, making it useful for many patients in the long-term management of angina pectoris. On the other hand, nadolol can increase oxygen requirements by increasing left ventricular fiber length and end diastolic pressure, particularly in patients with heart failure.

Although beta-adrenergic receptor blockade is useful in treatment of angina and hypertension, there are also situations in which sympathetic stimulation is vital. For example, in patients with severely damaged hearts, adequate ventricular function may depend on sympathetic drive. Beta-adrenergic blockade may worsen AV block by preventing the necessary facilitating effects of sympathetic activity on conduction. Beta 2-adrenergic blockade results in passive bronchial constriction by interfering with endogenous adrenergic bronchodilator activity in patients subject to bronchospasm and may also interfere with exogenous bronchodilators in such patients.

Absorption of nadolol after oral dosing is variable, averaging about 30 percent. Peak serum concentrations of nadolol usually occur in three to four hours after oral administration and the presence of food in the gastrointestinal tract does not affect the rate or extent of nadolol absorption. Approximately 30 percent of the nadolol present in serum is reversibly bound to plasma protein.

Unlike many other beta-adrenergic blocking agents, nadolol is not metabolized by the liver and is excreted unchanged, principally by the kidneys.

The half-life of therapeutic doses of nadolol is about 20 to 24 hours, permitting once daily dosage. Because nadolol is excreted predominantly in the urine, its half-life increases in renal failure (seePRECAUTIONSand DOSAGE AND ADMINISTRATION). Steady-state serum concentrations of nadolol are attained in six to nine days with once-daily dosage in persons with normal renal function. Because of variable absorption and different individual responsiveness, the proper dosage must be determined by titration.

Exacerbation of angina and, in some cases, myocardial infarction and ventricular dysrhythmias have been reported after abrupt discontinuation of therapy with beta-adrenergic blocking agents in patients with coronary artery disease. Abrupt withdrawal of these agents in patients without coronary artery disease has resulted in transient symptoms, including tremulousness, sweating, palpitation, headache, and malaise. Several mechanisms have been proposed to explain these phenomena, among them increased sensitivity to catecholamines because of increased numbers of beta receptors.

PRECAUTIONS

Impaired Renal Function

Nadolol should be used with caution in patients with impaired renal function (seeDOSAGE AND ADMINISTRATION****).

Information for Patients

Patients, especially those with evidence of coronary artery insufficiency, should be warned against interruption or discontinuation of nadolol therapy without the physician’s advice. Although cardiac failure rarely occurs in properly selected patients, patients being treated with beta-adrenergic blocking agents should be advised to consult the physician at the first sign or symptom of impending failure. The patient should also be advised of a proper course in the event of an inadvertently missed dose.

Drug Interactions

When administered concurrently, the following drugs may interact with beta- adrenergic receptor blocking agents:

Anesthetics, general- exaggeration of the hypotension induced by general anesthetics (seeWARNINGS, Major Surgery).

Antidiabetic drugs (oral agents and insulin)- hypoglycemia or hyperglycemia; adjust dosage of antidiabetic drug accordingly (seeWARNINGS, Diabetes and Hypoglycemia).

Catecholamine-depleting drugs (e.g., reserpine)- additive effect; monitor closely for evidence of hypotension and/or excessive bradycardia (e.g., vertigo, syncope, postural hypotension).

Digitalis glycosides- Both digitalis glycosides and beta-blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia.

Response to Treatment for Anaphylactic Reaction- While taking beta-blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic, or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.

Carcinogenesis, Mutagenesis, Impairment of Fertility

In chronic oral toxicologic studies (one to two years) in mice, rats, and dogs, nadolol did not produce any significant toxic effects. In two-year oral carcinogenic studies in rats and mice, nadolol did not produce any neoplastic, preneoplastic, or non-neoplastic pathologic lesions. In fertility and general reproductive performance studies in rats, nadolol caused no adverse effects.

Pregnancy

In animal reproduction studies with nadolol, evidence of embryotoxicity and fetotoxicity was found in rabbits, but not in rats or hamsters, at doses 5 to 10 times greater (on a mg/kg basis) than the maximum indicated human dose. No teratogenic potential was observed in any of these species.

There are no adequate and well controlled studies in pregnant women. Nadolol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Neonates whose mothers are receiving nadolol at parturition have exhibited bradycardia, hypoglycemia, and associated symptoms.

Nursing Mothers

Nadolol is excreted in human milk. Because of the potential for adverse effects in nursing infants, a decision should be made whether to discontinue nursing or to discontinue therapy taking into account the importance of nadolol to the mother.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.