PROPRANOLOL ADMINISTRATION IN INFANCY

Abstract

Propranolol, (P) the beta blocking agent has been used for treatment of arrhythmia and hypercyanotic spells in infancy. Very little firm data about pharmacologic parameters is available. This series involves P levels in 6 infants. One infant, born to a mother treated with 160 mg P/day had P levels which increased over the first 4 hrs. of life. Two newborns with atrial arrhythmia refractory to Digoxin were begun on small doses of P which were increased until a therapeutic result was obtained (at a dose of 1 mg/kg/24 hr.). Three infants ranging in age from 7-11 mos. (wgt.7-9 kg.) were treated with 2.5 mg/ kg/24 hr. in 4 divided oral doses for hypercyanotic spells. Serial (P) levels were obtained from 45 min. to 6 hrs. following the oral dose and these levels were incorporated into a curve from which the half-life (2.3 hrs.), the elimination, constant (0.005 min.-1) and the volume of distribution (8.13L/kg) of the drug were calculated. The P level decrease with respect to time was a straight line function which yielded a correlation coefficient with those from pharmacokinetic studies in adults. Conclusions: (1) Infants > 7 mos.; > 7 kg. on 2.5 mg/kg/24 hr. metabolize, distribute, and elimiP as adults. (2) In the neonate, these values may not apply and a dose of 1 mg/kg/24 hr. was therapeutic. (3) Given to pregnant women, the drug is stored in the fetal liver and the increased level reflects the inability of the fetus to adequately metabolize the drug.