Mesoporous silica-based dosage forms improve release characteristics of poorly soluble drugs: case example...

Mesoporous silica-based dosage forms offer the potential for improving the absorption of poorly soluble drugs after oral administration. In this investigation, fenofibrate was used as a model drug to study the ability of monomodal ('PSP A') and bimodal ('PSP B') porous silica to improve release by a 'spring' effect in in vitro biorelevant dissolution tests. Also investigated was the addition of various polymers to provide a 'parachute' effect, that is, to keep the drug in solution after its release.

Loading fenofibrate onto PSP A or PSP B porous silica substantially improved the dissolution profile of fenofibrate under fasted state conditions compared with both pure drug and the marketed product, TriCor® 145 mg. Adding a polymer such as hydroxypropyl methylcellulose acetate succinate, polyvinylpyrrolidone or copovidon (HPMCAS, PVP or PVPVA) sustains the higher release of fenofibrate from the PSP A silica, resulting in a combination 'spring and parachute' effect - loading the drug onto the silica causes a 'spring' effect while the polymer enhances the spring effect (HPMCAS, PVP) and adds a sustaining 'parachute'. Interestingly, a silica to polymer ratio of 4:1 w/w appears to have an optimal effect for fenofibrate (HPMCAS, PVP). Dissolution results under conditions simulating the fasted state in the small intestine with the PSP A or the PSP B silica with HPMCAS added in a 4:1 w/w ratio show very substantial improvement over the marketed, nanosized product (TriCor® 145 mg).

Further experiments to determine whether the highly positive effects on fenofibrate release observed with the silica prototypes investigated to date can be translated to further poorly soluble drugs and to what extent they translate into improved in-vivo performance are warranted.