The effectiveness of dextromethorphan (DM) for treating acute cough is still unclear. Yet, dextromethorphan is frequently administered to children as an antitussive. Dextromethorphan dosages are based on age rather than body weight, causing considerable inconsistency in the relative amount of drug that is administered.

The aim objective of this study is to determine whether a dose-response association can occur among a group of children when administered a single nocturnal dose of dextromethorphan for cough in an upper respiratory tract infection.

A large, double-blind and placebo-controlled trial of over-the-counter cough medications was conducted and the children received dextromethorphan. The administered doses according to the manufacturer recommendations were as follows: ages 2 to 5 years - 7.5 mg; ages 6 to 11 years - 15 mg and ages 12 to 18 years - 30 mg. This was in a range of 0.35 to 0.94 mg/kg per dose. Subjective parental evaluations of cough and sleep were acquired by using a 7-point Likert-type scale. It compared symptoms after taking the medication with symptoms the earlier night that was without medication. As a subdivision analysis of the group that took dextromethorphan, three dose ranges were compared.

Thirty-three patients (19 girls, 14 boys; median age, 4.90 [2.90-6.80] years; age range, 2.10-16.50 years) received dextromethorphan and completed the trial. There were no significant differences found for any of the outcome measures while comparing the effects of different doses of dextromethorphan. The observations did suggested to some extent symptomatic relief for patients who were receiving the medium-dose dextromethorphan (0.45 to <0.60 mg/kg per dose) or high-dose dextromethorphan (0.60-0.94 mg/kg per dose) as compared with low-dose dextromethorphan (0.35 to <0.45 mg/kg per dose). Adverse events were observed in the high dose group.

According to the observations, it suggested that there is potential for improved clinical symptom control with increasing doses of dextromethorphan. The study findings suggested that a dose of 0.5 mg/kg should be considered in future assessments of the antitussive effect of dextromethorphan in the paediatric population to balance the symptomatic relief and prevention of adverse events.

Source: Paul IM, Shaffer ML, Yoder KE, Sturgis SA, Baker MS, Berlin CM Jr. Dose-response relationship with increasing doses of dextromethorphan for children with cough. Clin Ther. 2004 Sep; 26(9):1508-14.