It was reported in the literature that individual plasma zolmitriptan profiles after oral administration show double peaks in some volunteers and, because of this, the time to reach Cmax (Tmax) may vary between 0.5 and 6 h and Tmax could be at the time of the first or second peak [33], [34] and [35]. The double peaks are not observed following intravenous (IV) doses of zolmitriptan, suggesting that this phenomenon is due to the prolonged absorption down the gastrointestinal tract rather than enterohepatic recirculation [11]. These findings confirm that zolmitriptan is a BCS class-III drug (highly soluble and poorly permeable) [10]. On the other hand, the sublingual absorption of zolmitriptan from BEST-5 and market tablet showed less variation in Tmax (1–1.5 and 1.5–2.5, respectively) which may be due to the rapid transport across the sublingual mucosa which is five times thinner than buccal mucosa and more obviously due to the bioenhancing effect of Sepitrap™ 80 in BEST-5 on the sublingual mucosa.
Statistically significant differences (p < 0.05) were found between the pharmacokinetic parameters AUC0–12 and AUC0–∞ determined for both BEST-5 and the market tablet. The 90% confidence intervals for the test/reference mean ratio of the log-transformed data of AUC0–12 and AUC0–∞ are (1.18–1.62) and (1.17–1.60), respectively. Thus, the 90% confidence interval cannot satisfy bioequivalence. There was no significant difference (p > 0.05) between the tested formulations in terms of t1/2 where its value complies with that reported in the literature [11]. Based on these findings, it could be concluded that a promising BEST of zolmitriptan was successfully designed. However, because of the small number of subjects recruited in the study, the results can only be considered preliminary, and further studies with a larger number of subjects should be conducted to prove the clinical usability of the developed bioenhanced sublingual formulation.