Solid dispersions as a technological strategy to improve the bioperformance of antiparasitic drugs with limited solubility

Albendazole (ABZ) and benznidazole (BZL) are drugs used in parasitic infections treatment and classified as class II drugs by the Biopharmaceutical Classification System (BCS) due to their low solubility, which limits their bioavailability. In this research, solid dispersion (SD) technology was used to enhance ABZ and BZL performance by increasing their dissolution rate and solubility. SDs were prepared by the fusion method, employing a triblock co-polymer, Poloxamer 407 (P407), as carrier to disperse 32 of BZL or 50% w/w of ABZ. Furthermore, physical mixtures (PM) of P407 and either ABZ or BZL were prepared in the same drug/polymer proportion, and then SDs and PMs were characterized. Dissolution tests of SDs, PMs and commercial formulations (CF) of ABZ and BZL were carried out and dissolution profiles were analyzed with the lumped mathematical model, which allowed obtaining different parameters of pharmaceutical relevance. The results indicated that SDs of ABZ presented an initial dissolution rate (IDR) 21-fold and 11-fold faster than PM and CF, respectively, while the IDR of BZL SD was 2.5-fold and 4.5-fold faster than CF of BZL, respectively. In the case of samples containing BZL, the time required to reach 80% dissolution of the drug (t_80%) was 4 (SD), 46 (PM), and 239 min (CF); while the dissolution efficiency (DE) values determined at 30 minutes were 85 (DS), 71 (MF) and 65% (FC). For the samples containing ABZ, t_80% was 2 (SD), value not reached (PM) and 40 min (CF); while the DE values determined at 30 minutes were 85 (SD), 36 (MF) and 65% (CF). The results showed that the SDs developed notably increased the dissolution rate, in consonance with the values obtained from the pharmaceutical parameters, which could lead to faster absorption and, consequently, increase the bioavailability of these drugs that are poorly soluble in water.