Inderal (propranolol hydrochloride) is a non-selective beta-adrenergic blocking agent, representing a cornerstone in cardiovascular and neurological pharmacotherapy. As a first-generation beta-blocker, it competitively antagonizes catecholamine effects at both β₁- and β₂-adrenergic receptors, producing negative chronotropic, inotropic, and dromotropic cardiac effects while modulating sympathetic nervous system activity. Its extensive evidence base, spanning over five decades of clinical use, supports its role in managing hypertension, angina pectoris, cardiac arrhythmias, myocardial infarction prophylaxis, essential tremor, migraine prophylaxis, and symptomatic management of thyrotoxicosis and pheochromocytoma. This comprehensive profile details its pharmacological characteristics, therapeutic applications, and clinical considerations for healthcare professionals.

Features

• Chemical name: 1-(Isopropylamino)-3-(1-naphthyloxy)-2-propanol hydrochloride
• Molecular formula: C₁₆H₂₁NO₂·HCl
• Molecular weight: 295.80 g/mol
• Appearance: White to off-white crystalline powder
• Solubility: Freely soluble in water and ethanol
• Mechanism: Non-selective beta-adrenergic receptor antagonist
• Bioavailability: Approximately 25% (extensive first-pass metabolism)
• Protein binding: 90-95% (primarily to albumin and alpha₁-acid glycoprotein)
• Half-life: 3-6 hours (extended to 8-11 hours with long-acting formulations)
• Metabolism: Hepatic (extensive via CYP2D6, CYP1A2, CYP2C19)
• Excretion: Primarily renal (less than 5% unchanged)

Benefits

• Provides reliable blood pressure control through reduction of cardiac output and inhibition of renin release
• Decreases myocardial oxygen demand, making it effective for angina prophylaxis and post-MI protection
• Controls ventricular rate in tachyarrhythmias by suppressing AV nodal conduction and ectopic pacemakers
• Redces tremor amplitude in essential tremor through central and peripheral beta-adrenergic blockade
• Decreases migraine frequency and severity by preventing cerebral arterial vasodilation and modulating trigeminovascular system
• Manages sympathetic overactivity symptoms in hyperthyroidism and pheochromocytoma (always with alpha-blockade)

Common use

Inderal is indicated for the management of hypertension, either as monotherapy or in combination with other antihypertensive agents. It is employed for angina pectoris prophylaxis, particularly in patients with coexisting hypertension or arrhythmias. The medication serves as effective therapy for cardiac arrhythmias including sinus tachycardia, atrial fibrillation, atrial flutter, and ventricular tachycardias. It is standard for secondary prevention after myocardial infarction to reduce mortality and reinfarction risk. Neurological applications include migraine headache prophylaxis and essential tremor management. Additional uses include symptomatic control of thyrotoxicosis (preoperatively and during radioactive iodine therapy), adjunctive management of pheochromocytoma (after alpha-blockade), and off-label uses such as performance anxiety, portal hypertension, and akathisia.

Dosage and direction

Dosage must be individualized based on indication and patient response. For hypertension: Initial dose 40 mg twice daily, increasing gradually to 120-240 mg daily in divided doses (maximum 640 mg daily). For angina: 80-320 mg daily in divided doses. For arrhythmias: 10-30 mg three or four times daily. For migraine prophylaxis: Start with 80 mg daily in divided doses, increase gradually to 160-240 mg daily. For essential tremor: 40 mg twice daily, maintenance 120-320 mg daily. Administer with food to enhance bioavailability. Tablets should be swallowed whole with water. Do not crush or chew extended-release formulations. Abrupt discontinuation may precipitate rebound hypertension or angina—taper gradually over 1-2 weeks.

Precautions

Use cautiously in patients with compensated heart failure; may worsen cardiac function in decompensated failure. May mask hypoglycemia symptoms in diabetics (tachycardia, tremor) while preserving sweating. Can produce bronchospasm in patients with reactive airway disease. May reduce peripheral circulation and exacerbate Raynaud’s phenomenon or peripheral arterial disease. Use lower doses in elderly patients due to reduced hepatic metabolism and increased sensitivity. Monitor hepatic and renal function periodically. May cause fatigue, dizziness, or visual disturbances affecting driving ability. Not recommended during pregnancy unless clearly needed (Category C). Appears in breast milk; consider risk-benefit.

Contraindications

Absolute contraindications include bronchial asthma, severe chronic obstructive pulmonary disease, cardiogenic shock, decompensated heart failure (unless secondary to tachyarrhythmia treatable with beta-blockers), severe bradycardia (heart rate <50 bpm), sick sinus syndrome (without permanent pacemaker), second- or third-degree AV block, severe hypotension (systolic <90 mmHg), and hypersensitivity to propranolol or components. Relative contraindications include diabetes mellitus (especially with frequent hypoglycemia), thyrotoxicosis (may mask symptoms), pheochromocytoma (must be alpha-blocked first), major depression, and hepatic impairment.

Possible side effect

Common side effects (≥1%) include fatigue (10-15%), dizziness (5-10%), bradycardia (5-10%), cold extremities (5-10%), nausea (5-10%), diarrhea (5-10%), and sleep disturbances (5-10%). Less common effects include bronchospasm (1-5%), depression (1-5%), impotence (1-5%), vivid dreams (1-5%), and worsening heart failure (1-5%). Rare but serious adverse reactions include hallucinations (<1%), exacerbation of psoriasis (<1%), agranulocytosis (<0.1%), thrombocytopenia (<0.1%), and Peyronie’s disease (<0.1%). Most side effects are dose-dependent and often diminish with continued therapy.

Drug interaction

Significant interactions occur with verapamil and diltiazem (additive bradycardia and AV block). Potentiates effects of other antihypertensives, antiarrhythmics, and negative chronotropic agents. NSAIDs may diminish antihypertensive effect. CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine) increase propranolol levels. May alter insulin and oral hypoglycemic requirements. Reduces clearance of lidocaine and theophylline. Concomitant use with clonidine requires careful monitoring (rebound hypertension risk). MAO inhibitors require at least 14-day washout period. Epinephrine may cause unopposed alpha-adrenergic effects. Alcohol may enhance hypotensive effect.

Missed dose

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double the dose to make up for a missed one. For twice-daily dosing, if remembered within 4 hours of next dose, skip missed dose. For once-daily formulations, take as soon as remembered unless next dose is due within 8 hours. Maintain regular scheduling to ensure consistent therapeutic effect. Patients should not adjust dosing frequency without medical supervision.

Overdose

Manifests as severe bradycardia, hypotension, heart failure, bronchospasm, hypoglycemia, and seizures. Cardiovascular effects include AV block, intraventricular conduction disturbances, cardiogenic shock, and asystole. CNS depression may progress to coma. Management includes gastric lavage if recent ingestion, activated charcoal, and supportive care. Specific antidotes include atropine for bradycardia, glucagon (50-150 mcg/kg IV) to reverse myocardial effects, and beta-agonists (isoproterenol, dobutamine) for refractory cases. Cardiac pacing may be necessary. Hemodialysis is not effective due to high protein binding.

Storage

Store at controlled room temperature (20-25°C or 68-77°F). Protect from light and moisture. Keep container tightly closed. Do not store in bathroom or near sink. Keep out of reach of children and pets. Do not use after expiration date printed on packaging. Do not transfer tablets to other containers as this may affect stability. Discard any medication that appears discolored or shows signs of deterioration.

Disclaimer

This information is for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, changing, or stopping any medication. Dosage and indications may vary based on individual patient factors, regional guidelines, and updated clinical evidence. The prescriber should review full prescribing information before administration. Not all possible uses, precautions, or interactions are listed here.

Reviews

Clinical studies demonstrate Inderal’s efficacy across multiple indications. The Beta-Blocker Heart Attack Trial (BHAT) showed 26% reduction in mortality post-MI. Hypertension trials indicate 10-15 mmHg systolic and 8-10 mmHg diastolic reductions. Migraine studies show 50-60% reduction in frequency in responsive patients. Essential tremor research demonstrates 50-70% subjective improvement. Most reviews note its well-established safety profile but emphasize need for appropriate patient selection. Specialist consensus maintains its role as valuable therapeutic option despite newer agents, particularly for patients with multiple indications.