Propranolol is a non-selective beta-adrenergic receptor antagonist (beta-blocker) that has been in clinical use since the 1960s. It was the first successful beta-blocker developed and has profoundly influenced cardiovascular medicine. Propranolol works by blocking beta-1 and beta-2 adrenergic receptors, thereby reducing the effects of adrenaline and noradrenaline on the heart, lungs, and vascular system. The result is a decrease in heart rate, blood pressure, and myocardial oxygen demand, which makes it useful in a wide range of cardiovascular conditions. Its lipophilic nature allows it to cross the blood-brain barrier, giving it additional neurological applications not shared by more hydrophilic beta-blockers.
Because it blocks both beta-1 and beta-2 receptors, propranolol affects the heart, peripheral vasculature, and the bronchial tree. This non-selectivity can be advantageous in conditions like thyrotoxicosis, migraine, and anxiety, but it also carries risks in asthma and chronic obstructive pulmonary disease (COPD) because beta-2 blockade can cause bronchoconstriction. Despite newer, more selective beta-blockers becoming available, propranolol remains one of the most versatile and widely prescribed agents, with applications extending from cardiology to psychiatry and neurology.
Propranolol is available in immediate-release tablets, long-acting capsules, and oral solutions. It is typically taken multiple times daily in its short-acting form or once daily in sustained-release formulations. The drug has a relatively short half-life (3–6 hours for immediate release), so formulation choice depends on indication and patient compliance factors. Clinical benefits are usually observed within hours to days of starting therapy, although some effects, such as migraine prophylaxis, may require weeks to manifest.
Dosage varies widely by indication, from 10–40 mg three to four times daily for anxiety, up to 320 mg/day for migraine prophylaxis or arrhythmias. Long-acting formulations simplify dosing to once daily.
Side effects are often dose-related and may be managed by lowering the dose, switching to a different beta-blocker, or supportive measures. Patients should not discontinue propranolol abruptly, as rebound tachycardia, hypertension, or angina may occur.
Patients should be educated about gradual discontinuation, signs of adverse effects, and the importance of adherence. Special caution is required in the elderly and in those taking multiple cardiovascular medications.
Patients should always keep a current medication list and review it with healthcare providers before starting or stopping any treatment.
Overdose: Symptoms may include profound bradycardia, hypotension, heart block, bronchospasm, seizures, and hypoglycaemia. Severe cases can be life-threatening. Treatment is supportive and may include intravenous fluids, atropine, glucagon, beta-agonists, high-dose insulin therapy, or pacing in refractory cases. Hospitalisation and continuous cardiac monitoring are required.
Accidental double dose: May cause increased fatigue, dizziness, or slower heart rate. Patients should rest, avoid driving, and contact a healthcare provider if they feel unwell.
Missed dose: Take as soon as remembered unless it is almost time for the next dose. Do not double up. Consistent adherence is important for stable control of cardiovascular conditions.
Education on recognising concerning symptoms (such as fainting, chest pain, or severe shortness of breath) is essential.
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