The propranolol hydrochloride component may cause bradycardia, cardiac failure, hypotension, or bronchospasm. Propranolol is not significantly dialyzable.
The hydrochlorothiazide component can be expected to cause diuresis. Lethargy of varying degree may appear and may progress to coma within a few hours, with minimal depression of respiration and cardiovascular function, and in the absence of significant serum electrolyte changes or dehydration. The mechanism of central nervous system depression with thiazide overdosage is unknown. Gastrointestinal irritation and hypermotility can occur, temporary elevation of BUN has been reported, and serum electrolyte changes could occur, especially in patients with impairment of renal function.
The oral LD50 dosages in rats and mice for propranolol, hydrochlorothiazide, and combined propranolol/hydrochlorothiazide (40/25, 80/25) are 364 to 533 mg/kg, greater than 2,750 to 5,000 mg/kg, and 538 to 845 mg/kg, respectively.
The following measures should be employed:
General—If ingestion is, or may have been, recent, evacuate gastric contents, taking care to prevent pulmonary aspiration.
Bradycardia—Administer atropine (0.25 to 1.0 mg). If there is no response to vagal blockade, administer isoproterenol cautiously.
Cardiac Failure—Digitalization and diuretics.
Hypotension—Vasopressors, e.g., levarterenol or epinephrine.
Bronchospasm—Administer isoproterenol and aminophylline.
Stupor or Coma—Administer supportive therapy as clinically warranted.
Gastrointestinal Effects—Though usually of short duration, these may require symptomatic treatment.
Abnormalities in BUN and/or Serum Electrolytes—Monitor serum electrolyte levels and renal function; institute supportive measures as required individually to maintain hydration, electrolyte balance, respiration, and cardiovascular-renal function.