The oral solid dosage forms are extremely relevant to drug therapy and responsible for much of the pharmaceutical industry turnover worldwide. However, the development of medicines in solid form involves significant challenges, including obtaining formulations with appropriate bioavailability for low aqueous solubility drugs (classes II and IV of the Biopharmaceutics Classification System). One of the most effective strategies to overcome poor dissolution rate and low absorption of drugs is the solid dispersion technique, however, although it has been the focus of much research in recent decades, there are relatively few commercially available products based on such technology. This is mainly due to problems related to production scale-up and physicochemical instability and creates opportunities for new studies to explore the full potential of the technology. This review presents an overall approach to the factors affecting the dissolution rate and oral bioavailability of BCS-classes II and IV drugs and a brief review of the state-of-the-art of solid dispersion technology.

RESUMO. O praziquantel é o fármaco de escolha no tratamento da esquistossomose, porém, sua baixa solubilidade aquosa pode comprometer sua biodisponibilidade por via oral. Neste trabalho o praziquantel foi incorporado em microesferas de poli(3-hidroxibutirato) (PHB) e Eudragit ® E pela técnica de emulsãoevaporação do solvente, com o intuito de melhorar sua solubilidade aquosa. As micropartículas preparadas com PHB apresentaram forma esférica e eficiência de encapsulação do fármaco de 78%. Quando preparadas com Eudragit ® E/PHB na proporção de 50/50, apresentaram-se porosas e com eficiência de encapsulação de 42%. As microesferas preparadas com os polímeros na proporção de 75/25 apresentaram-se mais porosas que as anteriores e com 52% de praziquantel encapsulado. Ensaios de dissolução in vitro demonstraram melhora significativa na solubilidade aquosa do praziquantel incorporado às microesferas de Eudragit ® E/PHB 75/25. O aumento da solubilidade está associado à elevada porosidade das microesferas e ao emprego do Eudragit ® E como carreador hidrofílico. Palavras-chave: microencapsulação, fármacos pouco solúveis. Evaluation of enhanced aqueous solubility of praziquantel incorporated in poly (3hydroxybutyrate) and Eudragit ® E microspheres ABSTRACT. Praziquantel is the drug of choice for the treatment of schistosomiasis, however, its low water solubility may undermine the oral bioavailability. In this study, praziquantel was incorporated into microspheres prepared with poly(3-hydroxybutyrate) (PHB) and a polymethacrylate (Eudragit ® E), using an emulsion-solvent evaporation method, in order to improve its aqueous solubility. Microparticles prepared with PHB had spherical shape and encapsulation efficiency of 78%. When prepared with Eudragit ® E/PHB at a ratio of 50/50 the microspheres were porous and encapsulated 42% of the drug, and for a ratio of 75/25 the microspheres were more porous than those of the previous formulations, with an encapsulation efficiency of 52%. Dissolution in vitro led to a significant improvement in the aqueous solubility of praziquantel incorporated into Eudragit ® E/PHB 75/25 microspheres. This increased solubility is linked to the high porosity of the microspheres and the use of Eudragit ® E as a hydrophilic carrier.