Nadolol

Nadolol is a white crystalline powder. It is freely soluble in ethanol, soluble in hydrochloric acid, slightly soluble in water and in chloroform, and very slightly soluble in sodium hydroxide.

Nadolol is designated chemically as 1-(tert-butylamino)-3-{(5,6,7,8-tetrahydro-cis-6,7-dihydroxy-1-naphthyl)oxy}-2-propanol. Structural formula:

Bendroflumethiazide

Bendroflumethiazide is a white crystalline powder. It is soluble in alcohol and in sodium hydroxide, and insoluble in hydrochloric acid, water, and chloroform.

Bendroflumethiazide is designated chemically as 3-benzyl-3,4-dihydro-6-(trifluoromethyl)-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide. Structural formula:

Nadolol

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 beta1 receptors located chiefly in cardiac muscle and the beta2 receptors 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. Beta2-adrenergic blockade may worsen AV block by preventing the necessary facilitating effects of sympathetic activity on conduction. Beta2-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 (see PRECAUTIONS, General, and 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.

Bendroflumethiazide

The mechanism of action of bendroflumethiazide results in an interference with the renal tubular mechanism of electrolyte reabsorption. At maximal therapeutic dosage all thiazides are approximately equal in their diuretic potency.

Thiazides increase excretion of sodium and chloride in approximately equivalent amounts. Natriuresis causes a secondary loss of potassium and bicarbonate.

The mechanism of the antihypertensive effect of thiazides is unknown. Thiazides do not affect normal blood pressure.

Onset of action of thiazides occurs in two hours and the peak effect at about four hours. Duration of action persists for approximately six to 12 hours. Thiazides are eliminated rapidly by the kidney.

Nadolol

Nadolol is contraindicated in bronchial asthma, sinus bradycardia and greater than first degree conduction block, cardiogenic shock, and overt cardiac failure (see WARNINGS).

Bendroflumethiazide

Bendroflumethiazide is contraindicated in anuria. It is also contraindicated in patients who have previously demonstrated hypersensitivity to bendroflumethiazide or other sulfonamide-derived drugs.

Nadolol

Bendroflumethiazide

Thiazides should be used with caution in severe renal disease. In patients with renal disease, thiazides may precipitate azotemia. Cumulative effects of the drug may develop in patients with impaired renal function.

Thiazides should be used with caution in patients with impaired hepatic function or progressive liver disease, since minor alterations of fluid and electrolyte balance may precipitate hepatic coma.

Sensitivity reactions may occur in patients with or without a history of allergy or bronchial asthma.

The possibility of exacerbation or activation of systemic lupus erythematosus has been reported.

Lithium generally should not be given with diuretics; diuretic agents reduce the renal clearance of lithium and add a high risk of lithium toxicity. Refer to the package insert for lithium preparations before use of such concomitant therapy.

General

Information for Patients

Patients, especially those with evidence of coronary artery insufficiency, should be warned against interruption or discontinuation of 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.

The patient should be informed of symptoms that would suggest potential adverse effects and told to report them promptly.

Laboratory Tests

Serum electrolyte levels should be regularly monitored (see WARNINGS, Bendroflumethiazide, also PRECAUTIONS, General, Bendroflumethiazide).

Drug Interactions

Drug/Laboratory Test Interactions

Bendroflumethiazide may produce false-negative results with the phentolamine and tyramine tests; may interfere with the phenosulfonphthalein test due to decreased excretion; and it may cause diagnostic interference of serum electrolyte levels, blood and urine glucose levels, and a decrease in serum PBI levels without signs of thyroid disturbance.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Nursing Mothers

Both nadolol and bendroflumethiazide are excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from both drugs, a decision should be made whether to discontinue nursing or to discontinue therapy taking into account the importance of nadolol and bendroflumethiazide tablets to the mother.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

Clinical studies of nadolol and bendroflumethiazide tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. This drug is known to be substantially excreted by the kidney, and the risk of toxic reaction to this drug may be greater in patients with impaired function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

Nadolol

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, and PRECAUTIONS).

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 1000 patients.

Respiratory-Bronchospasm has been reported in approximately 1 of 1000 patients (see CONTRAINDICATIONS and WARNINGS).

Gastrointestinal-Nausea, diarrhea, abdominal discomfort, constipation, vomiting, indigestion, anorexia, bloating, and flatulence have been reported in 1 to 5 of 1000 patients.

Miscellaneous-Each of the following has been reported in 1 to 5 of 1000 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.

Bendroflumethiazide

Gastrointestinal-Nausea, vomiting, cramping and anorexia are not uncommon; diarrhea, constipation, gastric irritation, abdominal bloating, jaundice (intrahepatic cholestatic jaundice), hepatitis, and sialadenitis occasionally occur; and pancreatitis has been reported.

Central Nervous System-Dizziness, vertigo, paresthesia, headache, and xanthopsia occasionally occur.

Hematologic-Leukopenia, agranulocytosis, thrombocytopenia, hemolytic anemia, and aplastic anemia have been reported.

Dermatologic-Hypersensitivity-Purpura, exfoliative dermatitis, pruritus, ecchymosis, urticaria, necrotizing angiitis (vasculitis, cutaneous vasculitis), respiratory distress including pneumonitis, fever, and anaphylactic reactions occasionally occur; photosensitivity and rash have been reported.

Cardiovascular-Orthostatic hypotension may occur and may be potentiated by coadministration with certain other drugs (e.g., alcohol, barbiturates, narcotics, other antihypertensive medications, etc.; see PRECAUTIONS, Drug Interactions).

Other-Muscle spasm, weakness, or restlessness is not uncommon; hyperglycemia, glycosuria, metabolic acidosis in diabetic patients, hyperuricemia, allergic glomerulonephritis, and transient blurred vision occasionally occur.

Whenever adverse reactions are moderate or severe, thiazide dosage should be reduced or therapy withdrawn.

To report SUSPECTED ADVERSE REACTIONS, contact IMPAX Laboratories, Inc. at 1-800-934-6729 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Treatment

Nadolol can be removed from the general circulation by hemodialysis. In determining the duration of corrective therapy, note must be taken of the long duration of the effect of nadolol. In addition to gastric lavage, the following measures should be employed, as appropriate.

Dosage Adjustment in Renal Failure

Absorbed nadolol is excreted principally by the kidneys and, although nonrenal elimination does occur, dosage adjustments are necessary in patients with renal impairment. The following dose intervals are recommended:

Storage

Store at 20°C to 25°C (68°F to 77°F) [see USP Controlled Room Temperature].

Dispense in a tightly-closed, light-resistant container as defined in the USP, with a child-resistant closure, as required.