What are the side effects of atenolol (beta-blocker)?

Side Effects of Atenolol

Atenolol's most common side effects include cold extremities, bradycardia, fatigue, dizziness, and respiratory symptoms in susceptible patients, with the drug being generally well tolerated but requiring careful monitoring for cardiac, metabolic, and central nervous system effects. 1

Cardiovascular Side Effects

The most prominent cardiovascular effects are directly related to beta-blockade:

• Bradycardia occurs in approximately 3% of patients on chronic therapy and 18% of patients receiving atenolol for acute myocardial infarction 1
• Cold extremities affect 12% of patients (compared to 5% on placebo), resulting from reduced peripheral blood flow 1
• Hypotension occurs in 25% of acute MI patients and 4% of chronic hypertension patients, often manageable by adjusting timing of concomitant ACE inhibitors or reducing diuretic doses 1
• Postural hypotension may occur with syncope in some patients, particularly when combined with other antihypertensive agents 1

Central Nervous System Effects

Atenolol causes fewer CNS side effects than lipophilic beta-blockers due to limited brain penetration:

• Fatigue affects 6% of patients (versus 5% on placebo), though only 0.4% discontinue therapy for this reason 2
• Dizziness occurs in 13% of patients (versus 6% on placebo) 1
• Lethargy affects 3% of patients 1
• Depression occurs in 12% of patients (versus 9% on placebo) 1
• Tiredness is reported in 26% of patients (versus 13% on placebo) 1

The lower lipid solubility of atenolol results in significantly fewer CNS effects compared to propranolol 3, 4

Respiratory Effects

Beta-1 selectivity makes atenolol safer than non-selective beta-blockers in respiratory disease, but caution is still required:

• Increased respiratory symptoms occur in asthma/COPD patients, though less commonly than with non-selective agents 2
• Wheeziness affects 3% of patients (similar to placebo at 3%) 1
• Dyspnea occurs in 6% of patients (versus 4% on placebo) 1
• Bronchospasm is reported in approximately 1.2% of acute MI patients 1

Patients with classical pulmonary asthma may worsen with atenolol despite its beta-1 selectivity 2

Metabolic Side Effects

Atenolol has unfavorable metabolic effects that distinguish it from newer beta-blockers:

• Lower HDL cholesterol and increased triglycerides occur with atenolol, similar to non-selective beta-blockers 2
• Increased incidence of new-onset type 2 diabetes was demonstrated in major trials (LIFE and ASCOT) 2
• Masking of hypoglycemia symptoms (particularly tachycardia) occurs in diabetic patients, especially those with type 1 diabetes or on insulin 2
• Impairment of glucose tolerance has been observed in diabetic patients 5

Gastrointestinal Effects

GI side effects are relatively uncommon:

• Diarrhea occurs in 3% of patients (versus 2% on placebo) 1
• Nausea affects 3% of patients (versus 1% on placebo) 1

Cardiac Conduction Effects

In acute myocardial infarction settings:

• Heart block (second or third degree) occurs in 4.5% of patients 1
• Cardiac failure occurred in 19% of atenolol-treated MI patients versus 24% on conventional therapy alone 1

Rare but Serious Side Effects

During post-marketing surveillance, the following have been reported:

• Elevated liver enzymes and/or bilirubin 1
• Psoriasiform rash or exacerbation of psoriasis 1
• Reversible alopecia 1
• Raynaud's phenomenon 1
• Lupus syndrome and antinuclear antibodies (ANA) 1
• Thrombocytopenia 1
• Impotence and Peyronie's disease 1

Overdose Manifestations

In overdose situations, the predominant symptoms are:

• Lethargy and disorder of respiratory drive 1
• Severe bradycardia and sinus pause 1
• Hypotension and congestive heart failure 1
• Bronchospasm and hypoglycemia 1

Patients have survived acute doses as high as 5 grams, though one death was reported with a possible 10-gram ingestion 1

Critical Management Considerations

Abrupt withdrawal of atenolol must be avoided, as it can precipitate severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias in patients with coronary artery disease 1

When discontinuation is necessary, patients should be carefully observed, advised to limit physical activity, and the drug should be tapered gradually rather than stopped abruptly 1

Atenolol should not be routinely withdrawn prior to major surgery, though the impaired ability of the heart to respond to reflex adrenergic stimuli may augment surgical risks 1

Special Population Concerns

In pregnancy, atenolol crosses the placental barrier and has been associated with infants small for gestational age when started in the second trimester 1

In elderly patients, lower doses are generally better tolerated due to decreased baroreceptor response and increased drug sensitivity 6

In patients with renal impairment, dosage must be reduced when glomerular filtration rate is less than 30 ml/min, as atenolol is eliminated virtually entirely unchanged in urine 4