Relative bioavailability and bioequivalence of a newly developed fixed combination sachet of acetylsalicylic acid and pseudoephedrine compared with a preliminary combination.

Acetylsalicylic acid (ASA) and pseudoephedrine (PSE) are often administered together for the treatment of symptoms of the common cold, i.e., nasal congestion, runny nose, sore throat and headache. Based on this fact we developed a fixed combination of 500 mg ASA and 30 mg PSE, the recommended doses for both drugs for treating symptoms of the common cold, as granulate to be dissolved in water for administration. The purpose of this open, randomized, three-factorial (three-treatment, three-period, six-sequence) Latin Square clinical study was to investigate the relative bioavailability of ASA and PSE as well as the establishment of bioequivalence after single administration of the fixed combination (final formulation for approval) of 500 mg ASA/30 mg PSE*HCl and the preliminary formulation of this combination. Pharmacokinetic characteristics AUC(norm) and C(max,norm) of ASA, its metabolite SA, and PSE, were determined as measure of rate and extent of absorption of the two formulations. The treatment ratios final/preliminary formulation and their corresponding 90% confidence intervals were calculated to establish bioequivalence. Additionally, descriptive statistics were calculated for the parameters t(max), t((1/2)), and mean residence time (MRT). In total, data from 18 healthy male volunteers were included in the pharmacokinetic evaluation. The primary target parameters were analyzed using an analysis of variance (ANOVA) after logarithmic transformation of the data. Confidence intervals of 90% were calculated for the geometric means of ratios using the mean square error term of the ANOVA. Bioequivalence criteria were fulfilled for AUC(norm) and C(max,norm). Geometric means of individual ratios of AUC(norm) and of C(max,norm) showed equal bioavailability of the new formulation compared with the preliminary. Furthermore, a relative bioavailability of approximately 100% of the preliminary formulation was shown for the newly developed formulation for all parameters. The parameters t(max), t((1/2)), and MRT showed comparable results for ASA, SA, and PSE, respectively, in both formulations. The supplementary evaluation for the non-normalized original parameters AUC and C(max) also revealed bioequivalence. For the newly developed formulation, the arithmetic means of the parameters AUC and C(max) for PSE were 1040.66 mg/h*l and 134.52 mg/l, for SA 142.28 mg/h*l and 30.34 mg/l, respectively. The median t(max) values were 0.67 h for PSE and 0.92 h for SA. Both treatments were safe and well tolerated.