The clinical pharmacology of brompheniramine in children.

Background: Brompheniramine has been widely used in the treatment of allergic rhinitis and other disorders during the past 4 decades. There are no published studies of its clinical pharmacology in children.

Objectives: This study was performed to test the hypothesis that brompheniramine would have a prompt onset of action and a 24-hour duration of action in children.

Methods: Before brompheniramine 4 mg was ingested, and at intervals from 0.5 to 30 hours thereafter, blood samples were obtained for quantitation of plasma brompheniramine concentrations by means of HPLC. Concurrently, epicutaneous tests with histamine phosphate were performed; wheals and flares were traced at 10 minutes, and the areas were measured by using a computerized digitizing system.

Results: In 14 children, mean age 9.5 +/- 0.4 years (SEM), the peak brompheniramine concentration was 7.7 +/- 0.7 ng/mL, and the time at which peak concentrations occurred was 3.2 +/- 0.3 hours. The terminal elimination half-life was 12.4 +/- 1.1 hours, and the oral clearance was 20.2 +/- 2.1 mL/min/kg. Compared with predose areas, the wheals and flares produced by histamine phosphate 1 mg/mL were significantly decreased from 0.5 to 30 hours and from 1 to 30 hours, respectively (P <.05), with mean maximum inhibition at 12 (52% +/- 9%) and 6 hours (72% +/- 10%), respectively.

Conclusions: In children a single dose of brompheniramine produces prompt, long-lasting peripheral H1 -blockade. Revised dosage regimens may be needed in this population.