Comparison of Echinacea alkylamide pharmacokinetics between liquid and tablet preparations

The relative oral bioavailability of alkylamides from two different Echinacea dosage forms (liquid and tablet) were compared in a small two-way crossover study in humans (n=3). The liquid preparation investigated contained a mixture of 'Echinacea purpurea' root (300 mg/ml) and 'Echinacea angustifolia' root (200 mg/ml) extracted in 60% ethanol. The tablet preparation investigated was also a mixture of 'E. purpurea' root (675 mg/tablet) and 'E. angustifolia' root (600 mg/tablet), but was prepared from the dried 60% ethanolic extracts of these two Echinacea species. Alkylamides were found to be rapidly absorbed and measurable in plasma from both preparations. No significant differences in the tetraene alkylamide pharmacokinetic parameters for T1/2, AUCt−lin and Cmax in the two different preparations were found. Tmax increased from 20 min for the liquid to 30 min for the tablet, which is not unexpected as the tablet required time for disintegration before absorption could occur. These results suggested that there was no significant difference in the bioavailability of alkylamides from the liquid and tablet Echinacea formulations. Furthermore, the results also indicated that the absorption site and any alkylamide loss due to digestive processes were similar in both preparations.