No specific information is available with regard to overdosage and atenolol and chlorthalidone in humans. Treatment should be symptomatic and supportive and directed to the removal of any unabsorbed drug by induced emesis, or administration of activated charcoal. Atenolol can be removed from the general circulation by hemodialysis. Further consideration should be given to dehydration, electrolyte imbalance and hypotension by established procedures.
Overdosage with atenolol has been reported with patients surviving acute doses as high as 5 g. One death was reported in a man who may have taken as much as 10 g acutely. The predominant symptoms reported following atenolol overdose are lethargy, disorder of respiratory drive, wheezing, sinus pause, and bradycardia. Additionally, common effects associated with overdosage of any beta-adrenergic blocking agent are congestive heart failure, hypotension, bronchospasm, and/or hypoglycemia. Other treatment modalities should be employed at the physician’s discretion and may include:
Bradycardia: Atropine 1-2 mg intravenously. If there is no response to vagal blockade, give isoproterenol cautiously. In refractory cases, a transvenous cardiac pacemaker may be indicated. Glucagon in a 10 mg intravenous bolus has been reported to be useful. If required, this may be repeated or followed by an intravenous infusion of glucagon 1-10 mg/h depending on response.
Heart Block (Second or Third Degree): Isoproterenol or transvenous pacemaker.
Congestive Heart Failure: Digitalize the patient and administer a diuretic. Glucagon has been reported to be useful.
Hypotension: Vasopressors such as dopamine or norepinephrine (levarterenol). Monitor blood pressure continuously.
Bronchospasm: A beta2-stimulant such as isoproterenol or terbutaline and/or aminophylline.
Hypoglycemia: Intravenous glucose.
Electrolyte Disturbance: Monitor electrolyte levels and renal function. Institute measures to maintain hydration and electrolytes.
Based on the severity of symptoms, management may require intensive support care and facilities for applying cardiac and respiratory support.
Symptoms of chlorthalidone overdose include nausea, weakness, dizziness and disturbances of electrolyte balance.