Medications: Inderal^® – propranolol

Inderal is indicated for:

• Hypertension
• Angina Pectoris
• Atrial Fibrillation
• Myocardial Infarction
• Migraine
• Essential Tremor
• Hypertrophic Subaortic Stenosis
• Pheochromocytoma

DOSAGE AND ADMINISTRATION

Hypertension

The usual initial dosage is 40 mg Inderal twice daily, whether used alone or added to a diuretic. Dosage may be increased gradually until adequate blood pressure control is achieved. The usual maintenance dosage is 120 mg to 240 mg per day. In some instances a dosage of 640 mg a day may be required. The time needed for full antihypertensive response to a given dosage is variable and may range from a few days to several weeks. While twice-daily dosing is effective and can maintain a reduction in blood pressure throughout the day, some patients, especially when lower doses are used, may experience a modest rise in blood pressure toward the end of the 12-hour dosing interval. This can be evaluated by measuring blood pressure near the end of the dosing interval to determine whether satisfactory control is being maintained throughout the day. If control is not adequate, a larger dose, or 3-times-daily therapy may achieve better control.

Angina Pectoris

Total daily doses of 80 mg to 320 mg Inderal, when administered orally, twice a day, three times a day, or four times a day, have been shown to increase exercise tolerance and to reduce ischemic changes in the ECG. If treatment is to be discontinued, reduce dosage gradually over a period of several weeks. (See WARNINGS.)

Atrial Fibrillation

The recommended dose is 10 mg to 30 mg Inderal three or four times daily before meals and at bedtime.

Myocardial Infarction

In the Beta-Blocker Heart Attack Trial (BHAT), the initial dose was 40 mg t.i.d., with titration after 1 month to 60 mg to 80 mg t.i.d. as tolerated. The recommended daily dosage is 180 mg to 240 mg Inderal per day in divided doses. Although a t.i.d. regimen was used in the BHAT and a q.i.d. regimen in the Norwegian Multicenter Trial, there is a reasonable basis for the use of either a t.i.d. or b.i.d. regimen (see PHARMACODYNAMICS AND CLINICAL EFFECTS). The effectiveness and safety of daily dosages greater than 240 mg for prevention of cardiac mortality have not been established. However, higher dosages may be needed to effectively treat coexisting diseases such as angina or hypertension (see above).

Migraine

The initial dose is 80 mg Inderal daily in divided doses. The usual effective dose range is 160 mg to 240 mg per day. The dosage may be increased gradually to achieve optimum migraine prophylaxis. If a satisfactory response is not obtained within four to six weeks after reaching the maximum dose, Inderal therapy should be discontinued. It may be advisable to withdraw the drug gradually over a period of several weeks.

Essential Tremor

The initial dosage is 40 mg Inderal twice daily. Optimum reduction of essential tremor is usually achieved with a dose of 120 mg per day. Occasionally, it may be necessary to administer 240 mg to 320 mg per day.

Hypertrophic Subaortic Stenosis

The usual dosage is 20 mg to 40 mg Inderal three or four times daily before meals and at bedtime.

Pheochromocytoma

The usual dosage is 60 mg Inderal daily in divided doses for three days prior to surgery as adjunctive therapy to alpha-adrenergic blockade. For the management of inoperable tumors, the usual dosage is 30 mg daily in divided doses as adjunctive therapy to alpha-adrenergic blockade.

The following adverse events were observed and have been reported in patients using propranolol.

• Cardiovascular: Bradycardia; congestive heart failure; intensification of AV block; hypotension; paresthesia of hands; thrombocytopenic purpura; arterial insufficiency, usually of the Raynaud type.
• Central Nervous System: Light-headedness, mental depression manifested by insomnia, lassitude, weakness, fatigue; catatonia; visual disturbances; hallucinations; vivid dreams; an acute reversible syndrome characterized by disorientation for time and place, short-term memory loss, emotional lability, slightly clouded sensorium, and decreased performance on neuropsychometrics. For immediate-release formulations, fatigue, lethargy, and vivid dreams appear dose-related.
• Gastrointestinal: Nausea, vomiting, epigastric distress, abdominal cramping, diarrhea, constipation, mesenteric arterial thrombosis, ischemic colitis.
• Allergic: Hypersensitivity reactions, including anaphylactic/anaphylactoid reactions, pharyngitis and agranulocytosis; erythematous rash, fever combined with aching and sore throat; laryngospasm, and respiratory distress.
• Respiratory: Bronchospasm.
• Hematologic: Agranulocytosis, nonthrombocytopenic purpura, thrombocytopenic purpura.
• Autoimmune: Systemic lupus erythematosus (SLE).
• Skin and mucous membranes: Stevens-Johnson Syndrome, toxic epidermal necrolysis, dry eyes, exfoliative dermatitis, erythema multiforme, urticaria, alopecia, SLE-like reactions, and psoriasiform rashes. Oculomucocutaneous syndrome involving the skin, serous membranes and conjunctivae reported for a beta blocker (practolol) have not been associated with propranolol.

Genitourinary: Male impotence; Peyronie’s disease.

Propranolol is contraindicated in 1) cardiogenic shock; 2) sinus bradycardia and greater than first degree block; 3) bronchial asthma; and 4) in patients with known hypersensitivity to propranolol hydrochloride.

WARNINGS AND PRECAUTIONS:

• Angina Pectoris: There have been reports of exacerbation of angina and, in some cases, myocardial infarction, following abrupt discontinuance of propranolol therapy.
• Hypersensitivity and Skin Reactions: Hypersensitivity reactions, including anaphylactic/anaphylactoid reactions, have been associated with the administration of propranolol (see ADVERSE REACTIONS). Cutaneous reactions, including Stevens-Johnson Syndrome, toxic epidermal necrolysis, exfoliative dermatitis, erythema multiforme, and urticaria, have been reported with use of propranolol
• Cardiac Failure: In Patients without a History of Heart Failure, continued use of beta blockers can, in some cases, lead to cardiac failure.
• Nonallergic Bronchospasm (e.g., Chronic Bronchitis, Emphysema): In general, patients with bronchospastic lung disease should not receive beta blockers. Propranolol should be administered with caution in this setting since it may provoke a bronchial asthmatic attack by blocking bronchodilation produced by endogenous and exogenous catecholamine stimulation of beta-receptors.
• Major Surgery: Chronically administered beta-blocking therapy should not be routinely withdrawn prior to major surgery, however the impaired ability of the heart to respond to reflex adrenergic stimuli may augment the risks of general anesthesia and surgical procedures.
• Diabetes and Hypoglycemia: Beta-adrenergic blockade may prevent the appearance of certain premonitory signs and symptoms (pulse rate and pressure changes) of acute hypoglycemia, especially in labile insulin dependent diabetics. In these patients, it may be more difficult to adjust the dosage of insulin.
• Thyrotoxicosis: Beta-adrenergic blockade may mask certain clinical signs of hyperthyroidism. Therefore, abrupt withdrawal of propranolol may be followed by an exacerbation of symptoms of hyperthyroidism, including thyroid storm. Propranolol may change thyroid-function tests, increasing T4 and reverse T3 and decreasing T3.
• Wolff-Parkinson-White Syndrome: Beta-adrenergic blockade in patients with Wolf-Parkinson-White Syndrome and tachycardia has been associated with severe bradycardia requiring treatment with a pacemaker.
• Pheochromocytoma: Blocking only the peripheral dilator (beta) action of epinephrine with propranolol leaves its constrictor (alpha) action unopposed. In the event of hemorrhage or shock, there is a disadvantage in having both beta and alpha blockade since the combination prevents the increase in heart rate and peripheral vasoconstriction needed to maintain blood pressure.
• Propranolol should be used with caution in patients with impaired hepatic or renal function.
• Inderal is not indicated for the treatment of hypertensive emergencies.
• Beta-adrenergic receptor blockade can cause reduction of intraocular pressure. Patients should be told that Inderal may interfere with the glaucoma screening test. Withdrawal may lead to a return of increased intraocular pressure.
• 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
• In patients with hypertension, use of propranolol has been associated with elevated levels of serum potassium, serum transaminases and alkaline phosphatase. In severe heart failure, the use of propranolol has been associated with increases in Blood Urea Nitrogen.
• Drug Interactions: Caution should be exercised when Inderal is administered with drugs that have an effect on CYP2D6, 1A2, or 2C19 metabolic pathways. Co-administration of such drugs with propranolol may lead to clinically relevant drug interactions and changes on its efficacy and/or toxicity (see Drug Interactions in PHARMACOKINETICS AND DRUG METABOLISM).
• Carcinogenesis, Mutagenesis, Impairment of Fertility
• Pregnancy: Pregnancy Category C
• Nursing mothers: Propranolol is excreted in human milk. Caution should be exercised when Inderal is administered to a nursing woman.
• Pediatric Use Safety and effectiveness of propranolol in pediatric patients have not been established.
• Geriatric Use: Clinical studies of Inderal 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.

Interactions with Substrates, Inhibitors or Inducers of Cytochrome P-450 Enzymes Because propranolol’s metabolism involves multiple pathways in the cytochrome P-450 system (CYP2D6, 1A2, 2C19), co-administration with drugs that are metabolized by, or effect the activity (induction or inhibition) of one or more of these pathways may lead to clinically relevant drug interactions (see Drug Interactions under PRECAUTIONS).

• Substrates or Inhibitors of CYP2D6: Blood levels and/or toxicity of propranolol may be increased by co-administration with substrates or inhibitors of CYP2D6, such as amiodarone, cimetidine, delavudin, fluoxetine, paroxetine, quinidine, and ritonavir. No interactions were observed with either ranitidine or lansoprazole.
• Substrates or Inhibitors of CYP1A2: Blood levels and/or toxicity of propranolol may be increased by co-administration with substrates or inhibitors of CYP1A2, such as imipramine, cimetidine, ciprofloxacin, fluvoxamine, isoniazid, ritonavir, theophylline, zileuton, zolmitriptan, and rizatriptan.
• Substrates or Inhibitors of CYP2C19: Blood levels and/or toxicity of propranolol may be increased by co-administration with substrates or inhibitors of CYP2C19, such as fluconazole, cimetidine, fluoxetine, fluvoxamine, tenioposide, and tolbutamide. No interaction was observed with omeprazole.
• Inducers of Hepatic Drug Metabolism: Blood levels of propranolol may be decreased by co-administration with inducers such as rifampin, ethanol, phenytoin, and phenobarbital. Cigarette smoking also induces hepatic metabolism and has been shown to increase up to 77% the clearance of propranolol, resulting in decreased plasma concentrations.

Cardiovascular Drugs:

• Antiarrhythmics – The AUC of propafenone is increased by more than 200% by co-administration of propranolol. The metabolism of propranolol is reduced by co-administration of quinidine, leading to a two-three fold increased blood concentration and greater degrees of clinical beta-blockade. The metabolism of lidocaine is inhibited by co-administration of propranolol, resulting in a 25% increase in lidocaine concentrations.
• Calcium Channel Blockers – The mean Cmax and AUC of propranolol are increased, respectively, by 50% and 30% by co-administration of nisoldipine and by 80% and 47%, by co-administration of nicardipine. The mean Cmax and AUC of nifedipine are increased by 64% and 79%, respectively, by co-administration of propranolol. Propranolol does not affect the pharmacokinetics of verapamil and norverapamil. Verapamil does not affect the pharmacokinetics of propranolol.

Non-Cardiovascular Drugs:

• Migraine Drugs – Administration of zolmitriptan or rizatriptan with propranolol resulted in increased concentrations of zolmitriptan (AUC increased by 56% and Cmax by 37%) or rizatriptan (the AUC and Cmax were increased by 67% and 75%, respectively).
• Theophylline – Co-administration of theophylline with propranolol decreases theophylline oral clearance by 30% to 52%.
• Benzodiazepines – Propranolol can inhibit the metabolism of diazepam, resulting in increased concentrations of diazepam and its metabolites. Diazepam does not alter the pharmacokinetics of propranolol. The pharmacokinetics of oxazepam, triazolam, lorazepam, and alprazolam are not affected by co-administration of propranolol.
• Neuroleptic Drugs – Co-administration of long-acting propranolol at doses greater than or equal to 160 mg/day resulted in increased thioridazine plasma concentrations ranging from 55% to 369% and increased thioridazine metabolite (mesoridazine) concentrations ranging from 33% to 209%. Co-administration of chlorpromazine with propranolol resulted in a 70% increase in propranolol plasma level.
• Anti-Ulcer Drugs – Co-administration of propranolol with cimetidine, a non-specific CYP450 inhibitor, increased propranolol AUC and Cmax by 46% and 35%, respectively. Co-administration with aluminum hydroxide gel (1200 mg) may result in a decrease in propranolol concentrations. Co-administration of metoclopramide with the long-acting propranolol did not have a significant effect on propranolol’s pharmacokinetics.
• Lipid Lowering Drugs – Co-administration of cholestyramine or colestipol with propranolol resulted in up to 50% decrease in propranolol concentrations. Co-administration of propranolol with lovastatin or pravastatin, decreased 18% to 23% the AUC of both, but did not alter their pharmacodynamics. Propranolol did not have an effect on the pharmacokinetics of fluvastatin.
• Warfarin – Concomitant administration of propranolol and warfarin has been shown to increase warfarin bioavailability and increase prothrombin time.
• Alcohol – Concomitant use of alcohol may increase plasma levels of propranolol.

Propranolol is not significantly dialyzable. In the event of overdosage or exaggerated response, the following measures should be employed: General: If ingestion is or may have been recent, evacuate gastric contents, taking care to prevent pulmonary aspiration.

Supportive Therapy: Hypotension and bradycardia have been reported following propranolol overdose and should be treated appropriately. Glucagon can exert potent inotropic and chronotropic effects and may be particularly useful for the treatment of hypotension or depressed myocardial function after a propranolol overdose. Glucagon should be administered as 50­ 150 mcg/kg intravenously followed by continuous drip of 1-5 mg/hour for positive chronotropic effect. Isoproterenol, dopamine or phosphodiesterase inhibitors may also be useful. Epinephrine, however, may provoke uncontrolled hypertension. Bradycardia can be treated with atropine or isoproterenol. Serious bradycardia may require temporary cardiac pacing. The electrocardiogram, pulse, blood pressure, neurobehavioral status and intake and output balance must be monitored. Isoproterenol and aminophylline may be used for bronchospasm.