Acetylsalicylic acid (CAS 50-78-2, ASA) and pseudoephedrine (CAS 90-82-4, PSE) both are remedies given together for the treatment of the symptoms of a common cold, i.e. mainly nasal congestion, running nose, sore throat and headache. The aim of this open, randomized, three-factorial (three-treatment, three-period, six-sequence) Latin Square clinical study was to investigate if there were any pharmacokinetic interactions between ASA and PSE when given as fixed combination of 500 mg ASA/30 mg PSE.HCl. Lack of interaction was assessed by determination of pharmacokinetic characteristics and relative bioavailability of both substances and salicylic acid (CAS 69-72-7, SA), administered in combination and as equally single dosed drugs. In total, the data of 12 healthy male volunteers were included into the pharmacokinetic evaluation. Primary target parameters were ratios combination/equally dosed single drugs of AUCnorm and Cmax, norm of ASA, its metabolite SA and PSE. The primary target parameters were analyzed using an analysis of variance (ANOVA) after logarithmic transformation of the data. 90% confidence intervals were calculated for the geometric means of ratios using the mean square error term of the ANOVA.
Results: Bioequivalence was given for AUCnorm and Cmax, norm for all ratios calculated. No interaction was found for AUCnorm and Cmax, norm between the fixed combination ASA/PSE and the equally single dosed drugs as reference. The supplementary evaluation for the non-normalized original parameters AUC and Cmax also revealed bioequivalence. All treatments were safe and well tolerated.