Supraventricular tachycardia treated with continuous infusions of propranolol.

Because oral therapy is often contraindicated in hospitalized patients we assessed the safety and efficacy of continuous intravenous propranolol infusions in nine patients with refractory supraventricular tachycardia. Standard pharmacokinetic formulas predicted a loading dose (52.2 +/- 38.3 micrograms/kg), steady-state plasma concentration, and the initial maintenance dose (16.1 +/- 16.2 micrograms/kg/hr; range 6.1 to 56.0 micrograms/kg/hr) to control heart rate. Subsequent maintenance doses (3.9 to 74.9 micrograms/kg/hr) were determined by clinical response. Heart rate decreased from 146 +/- 22 to 98 +/- 16 beats/min (p less than 0.0001). This decrease persisted throughout the infusion. Measured propranolol levels (28 +/- 21 ng/ml) did not differ significantly from the predicted levels (23 +/- 17 ng/ml). The duration of the infusion averaged 97 +/- 77 hours. A side effect, transient wheezing, occurred in only one patient. This resolved when the infusion rate was decreased. We conclude that continuous propranolol infusions appear safe and effective in treating these patients with supraventricular tachycardia.