What are the side effects of propranolol?

Propranolol Side Effects

Propranolol causes a wide range of adverse effects across multiple organ systems, with the most clinically significant being cardiovascular (bradycardia, hypotension), respiratory (bronchospasm), metabolic (hypoglycemia, especially in children), and central nervous system effects (sleep disturbances, lethargy, nightmares). 1

Cardiovascular Side Effects

• Bradycardia and hypotension are the most common cardiovascular effects due to beta-receptor blockade, occurring frequently but typically remaining mild and asymptomatic in patients without cardiac comorbidities 2, 3
• Cold extremities and arterial insufficiency (Raynaud-type) result from peripheral vasoconstriction and occur commonly 1, 3
• Intensification of AV block, congestive heart failure, and paresthesia of hands can occur 1
• Thrombocytopenic purpura has been reported 1

Clinical Pitfall: While bradycardia and hypotension are expected, clinically symptomatic cases requiring intervention are uncommon (0.1% for bradycardia in one large pediatric series) 2

Respiratory Side Effects

• Propranolol is absolutely contraindicated in asthma and should be used with extreme caution in chronic obstructive pulmonary disease due to β₂-receptor blockade causing bronchoconstriction 3, 1
• Bronchial irritation, hyperreactivity, bronchospasm, and cold-induced wheezing occur in 3-13% of patients 2, 3
• Respiratory adverse effects may require temporary discontinuation or dose reduction 2

Critical Warning: Propranolol does NOT cause isolated rhinorrhea—if a patient develops a runny nose, investigate alternative causes such as viral infection, allergic rhinitis, or other medications 3

Central Nervous System and Psychiatric Effects

• Sleep disturbances are common (2-18.5% of patients), including insomnia, nightmares, night terrors, and nocturnal agitation, due to propranolol's lipophilic properties allowing blood-brain barrier penetration 2, 3, 4
• Lethargy and fatigue are dose-related effects that appear more pronounced in elderly patients and those with reduced hepatic clearance 5, 1
• Mental depression manifested by lassitude and weakness occurs 1
• Visual disturbances, hallucinations, and vivid dreams are reported 1
• An acute reversible syndrome characterized by disorientation, short-term memory loss, emotional lability, and clouded sensorium can occur 1

Management Strategy for Sleep Disturbances: Consider dose reduction, earlier-evening dosing to minimize nighttime effects, or switching to a less lipophilic beta-blocker with reduced blood-brain barrier penetration 4, 5

Metabolic and Endocrine Effects

• Hypoglycemia is particularly dangerous in infants and children, occurring due to effects on glycogenolysis and gluconeogenesis 2, 1
• Beta-blockade masks early warning signs of hypoglycemia (sweating, tachycardia, shakiness), while late manifestations include lethargy, poor feeding, apnea, seizures, and loss of consciousness 2
• Hypoglycemia risk increases during fasting (including preoperative periods), after prolonged exercise, and in patients with renal insufficiency 3, 1
• Hyperglycemia has also been reported 3
• Propranolol may mask clinical signs of hyperthyroidism and alter thyroid function tests (increasing T4 and reverse T3, decreasing T3) 1

Critical Safety Measure in Pediatrics: Administer oral propranolol with feeds and hold therapy during periods of restricted oral intake to prevent hypoglycemia and hypoglycemia-induced seizures 2

Gastrointestinal Effects

• Nausea, vomiting, epigastric distress, abdominal cramping, diarrhea, and constipation are common 1
• Rare but serious: mesenteric arterial thrombosis and ischemic colitis 1
• Gastrointestinal symptoms tend to be dose-dependent and may respond to cautious dose reduction 3

Musculoskeletal Effects

• Musculoskeletal aches and pain, predominantly involving the legs and feet, are dose-dependent and often respond to dose reduction 3, 1

Dermatologic and Allergic Reactions

• Hypersensitivity reactions including anaphylactic/anaphylactoid reactions have been reported 1
• Serious cutaneous reactions: Stevens-Johnson Syndrome, toxic epidermal necrolysis, exfoliative dermatitis, erythema multiforme 1
• Urticaria, alopecia, SLE-like reactions, and psoriasiform rashes occur 1
• Dry eyes have been reported 1

Hematologic Effects

• Agranulocytosis (with pharyngitis, fever, aching, and sore throat) 1
• Thrombocytopenic and nonthrombocytopenic purpura 1

Genitourinary Effects

• Male impotence and Peyronie's disease are recognized adverse effects 1

Special Warnings and Severe Toxicity

• Abrupt discontinuation can cause exacerbation of angina, myocardial infarction, or thyroid storm—always taper gradually over at least several weeks 1
• In overdose (≥2,000 mg in isolated ingestions), severe toxicity occurs in approximately 50% of cases, including seizures, coma, cardiac arrest, and death 6
• Severe toxicity in overdose includes seizures (8%), coma (14%), need for inotropes (20%), sodium channel blockade (8%), and cardiac arrest (3%) 6

Dose-Related Patterns

• Fatigue, lethargy, and vivid dreams are dose-related with immediate-release formulations 1
• Both nausea and musculoskeletal symptoms respond to reducing propranolol to the smallest effective dose 3

Patient Education Priorities

Clinicians must educate caregivers and patients about: 2

• Sleep disturbances and their management options
• Bronchial irritation and when to seek care
• Signs of clinically symptomatic bradycardia and hypotension
• Hypoglycemia risk and the importance of taking medication with food (especially in children)