Beta-blockers cause bradycardia, hypotension, syncope and heart failure. Propranolol can cause coma and convulsions in severe cases.
Acute massive overdoses must be managed in hospital. While transferring, maintain airway and ventilation.
For severe bradycardia with a pulse under 40 beats per minute, give atropine 600mcg for an adult (3mg if in a hospital environment) and 40mcg/kg for a child.