Pharmacokinetic comparison of a dextromethorphan-salbutamol combination tablet and a plain dextromethorphan tablet

We compared in this double-blind crossover study the bioavailability of dextromethorphan from a dextromethorphan-salbutamol combination tablet (Redol comp) and from a plain dextromethorphan tablet (Extuson) by determining dextrorphan concentrations after single-dose oral administration in 10 healthy volunteers. The absorption of salbutamol from the combined preparation was also determined. The absorption of dextromethorphan was slightly faster from the plain dextromethorphan preparation. The peak concentration of dextrorphan was achieved at 1.5 h after Extuson and at 2 h after Redol comp (1,053.0 +/- 366.5 ng/ml and 901.5 +/- 210.9 ng/ml, NS). AUC0-12 values of dextrorphan were 4,315.6 +/- 295.0 (ng/ml)h after Extuson and 3,983.8 +/- 205.6 (ng/ml)h after Redol comp (p less than 0.05). Salbutamol was well absorbed from the combined preparation and the peak concentration was achieved at 3 h (6.57 +/- 2.95 ng/ml). Four subjects reported side-effects typical for salbutamol after the combination tablet. No side-effects were reported after the plain dextromethorphan tablet. On the basis of the present study, we conclude that the absorption of dextromethorphan from the preparations tested is almost equal and the dextromethorphan-salbutamol combination can be administered in tablet form for the treatment of cough.