## 3 Results and Discussion
### Dissolution Test Results and Korsmeyer-Peppas Release Kinetics
The release of MLT from the F3, F11 formulations, and Circadian\({}^{\circledR}\), at t = 2 h, shows a very similar release pattern. Formulation F3, at t \(\geq\) 3 h, exhibits faster MLT release than the other three, rendering it a suitable candidate for confronting sleep onset problems. From the F7 formulation, which contains a larger quantity of HMPC, MLT release is 34.2%, at t = 2 h, and remains low, reaching 80.1%, at t = 8 h. This slower release rate is related to the greater amount of HPMC used [64; 65; 66]. In view of this, F7 could be considered as a promising formulation in dealing with sleep maintenance dysfunctions. The F11 formulation, at t \(\geq\) 2 h, shows an average % MLT release pattern, when compared with the other two PLA-glycerol containing formulations. According to the MLT release kinetics data, obtained from the Korsmeyer-Peppas equation (Table 3), it is concluded that the F3, F7, and F11 formulations follow a non-Fickian/anomalous diffusion release mechanism (0.45 < n < 0.89), i.e., a combination of simple diffusion and Case II anomalous diffusion transport. Figure 6e,f, depicts the % MLT release vs. time from the F4, F8, F12, F13, F14, F15, F16 formulations, and Circadian\({}^{\circledR}\). These formulations are comprised of the same polymeric material, PLA-pentaerythitol, differing, however, in the relative amounts of this excipient and in the relative amounts of the other formulants they are fabricated from. MLT release from the F4 formulation is the highest of all, conversely to the hormone release from F8, being the lowest of all the remaining PLA-pentaerythitol containing formulations. This is due to the 7.4-fold increase in the amount of HPMC in F8 compared to F4 and the double PLA-pentaerythitol content in F4 (67 mg vs. 33 mg). Thus, F4 could be viewed as a sleep onset promoting formulation, with F8 as a sleep maintenance pharmaceutical product. Interestingly, the release of MLT from the F12 formulation is very similar to that from Circadian\({}^{\circledR}\), differing from F4 only in the relevant amounts of sodium alginate they contain;in F4 the amount of sodium alginate is 11-fold higher than in F12. It is well documented that at pH \(\geq\) 3, sodium alginate exists as a salt, and not in the form of alginic acid, which, conversely to the salt, does not facilitate the aqueous dissolution of the APIs. Thus, the higher the content of sodium alginate in a formulation, the greater is the dissolution enhancement. In view of these findings, it could be suggested that the F4 formulation is a suitable candidate for dealing with sleep onset dysfunctions, whilst the F8 formulation could be suggested for confronting sleep maintenance problems. Their congeneric F12 formulation seems to be a promising Circadin(r) competitor. According to the data, in terms of MLT release kinetics obtained for the F4 and F12 formulations, via the Korsmeyer-Peppas equation (Table 3), it is concluded that the hormone release follows a non-Fickian/anomalous diffusion release mechanism (0.45 \(<\) n \(<\) 0.89), i.e., a combination of simple diffusion and Case II anomalous diffusion transport. Apart from the F15 formulation the rest of the PLA-pentaerythnitol formulations (F13, F14, and F16, Figure 6f) have incremental differences in their composition, and this is mirrored in their release profiles. It is worth mentioning that the release of the hormone from F14 follows a very similar pattern to that from Circadin(r) at t \(\geq\) 4 h.  
According to the data on the MLT release kinetics from the F13, F14, F15, and F16 formulations, obtained by the Korsmeyer-Peppas equation (Table 3), it is concluded that a non-Fickian/anomalous diffusion release mechanism (0.45 \(<\) n \(<\) 0.89)--i.e., a combination of simple diffusion and Case II anomalous diffusion transport--is followed. Preliminary findings suggest that the formulations maintain a reproducible release profile within the initial study period.