Dextromethorphan hydrobromide (DM) is an antitussive cough syrup that is used widely. The objective of this study is to determine the basic pharmacokinetic characteristics of dextromethorphan hydrobromide along with its active metabolite, dextrorphan in children and adolescents.

Thirty-eight male and female participants who were at risk for developing an upper respiratory tract infection (URTI), or were symptomatic with cough due to URTI, were registered in a single-dose, open-label study. The age groups divided were 2-5 years in Group A (n = 8), 6-11 years in Group B (n = 17), 12-17 years in Group C (n = 13). Participants were genotyped for cytochrome P450 (CYP) 2D6 polymorphisms and categorized as poor or non-poor metabolizers. Groups A and B were given doses by an age-weight dosing schedule (7.5-24.75 mg of DM range) and a 30 mg dose was given to Group C.

The total average exposure to dextrorphan increased as the age group increased. The average exposure to dextromethorphan hydrobromide was uppermost in the adolescent group. One participant in that group was a non-poor metabolizer. The terminal half-life (t ½) values were lengthier in the adolescent group. There was no association between body weight and pharmacokinetic parameters. 

The study concluded that it is the first assessment of the pharmacokinetic characteristics of dextromethorphan hydrobromide in children and adolescents. A single dose of dextromethorphan hydrobromide in this population was very safe and also well tolerated at all tested doses.

Source: Guenin E, Armogida M, Riff D. Pharmacokinetic profile of dextromethorphan hydrobromide in a syrup formulation in children and adolescents. Clin Drug Investig. 2014 Sep;34(9):609-16. doi: 10.1007/s40261-014-0210-5. PMID: 25027615.