Symptoms: Overdosage of Betaloc ZOK may lead to severe hypotension, sinus bradycardia, atrioventricular block, heart failure, cardiogenic shock, cardiac arrest, bronchospasm, impairment of consciousness/coma, nausea, vomiting and cyanosis. Concomitant ingestion of alcohol, antihypertensives, quinidine or barbiturates may aggravate the patient's condition. The first manifestations of overdosage may be observed 20 min to 2 hrs after the drug's ingestion.
Treatment: Activated charcoal, if necessary gastric lavage. In the presence of severe hypotension, bradycardia and impending heart failure, administer a β1-agonist (eg, prenalterol) IV at 2-5 min intervals or as continuous infusion until the desired effect is achieved. Where a selective β1-agonist is not available, dopamine may be used; or atropine sulfate IV may be used in order to block the vagus nerve.
If a satisfactory effect is not achieved, other sympathomimetic agents eg, dobutamine may be used or noradrenaline may be given.
Glucagon in a dose of 1-10 mg can also be administered. Pacemaker may be necessary. To combat bronchospasm, a β2-agonist can be given IV.
Observe that the dosages of drugs (antidotes) needed to treat overdose of β-blockade are much higher than normally recommended therapeutic dosages. This is because β-receptors are occupied by the β-blocker.