Interaction with Modified Cyclodextrin as a Way to Increase the Antimalarial Activity of Primaquine

Background: Malaria is still a dangerous disease that impacts specifically Africa, Asia, and Latin America. The development of therapies to overcome the parasite infection is an important challenge nowadays. The medicine primaquine (PQ) is used in the treatment, although several side effects and low oral bioavailability are reported. Objective: This work focused on the preparation and characterization of a complex between PQ and 2- hydroxypropyl-β-cyclodextrin (HPCD), besides performing release tests of this formulation. Methods: PQ:HPCD complexes were prepared at 1:1 and 1:2 molar ratios, by the lyophilization method. The association between PQ and HPCD was tested using UV-vis, infrared (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy and NMR techniques (chemical shift, Job Plot, DOSY, and ROESY). Tests were also conducted to evaluate drug release before and after complexation with HPCD. Results: Results showed that there was a weak interaction of PQ with HPCD, forming non-inclusion complexes. These results were supported by FTIR results and spatial correlations between hydrogens from PQ with the external HPCD hydrogens. A 1:2 PQ:HPCD preferred molar ratio was determined by DSC and Job Plot experiments and the time to release 96% of the drug was 21.2 h slower after complexation. Conclusion: Conclusion indicate that PQ interacts poorly with HPCD, probably due to its hydrophilic character, as well as to its interaction with the external rim of HPCD. Our results demonstrate that there was a significant improvement in the release time after the complexation process, which could lead to an increase in the activity of the drug.