Could the small molecules such as amino acids improve aqueous solubility and stabilize amorphous systems containing Griseofulvin?

Abstract

Griseofulvin (GSF) is an antifungal drug that has low aqueous solubility and low oral bioavailability. Amorphous systems are capable to promote rapid drug dissolution, usually affording concentrations above drug solubility in the gastrointestinal tract (supersaturation) in order to promote better absorption. Thus, the aim of this work was to evaluate the ability of amino acids, as hydrophilic carriers, to improve drug kinetic solubilization and to stabilize GSF supersaturated solutions, as well as to stabilize GSF amorphous systems at solid-state. The effect of 5 amino acids on GSF precipitation behavior was investigated by solvent shift method. Amorphous systems were developed by ball milling (GSF + amino acid 1:1 M ratio) and Quench Cooling (to obtain GSF QC) techniques. The samples were characterized by solid-state techniques, submitted to in vitro kinetic solubility studies and evaluated under stability tests. Aspartic acid, methionine, valine and tryptophan demonstrated similar anti-precipitant abilities in phosphate buffer pH 6.5. However, in FaSSIF biorelevant medium, tryptophan was only one able to slow down the drug precipitation. The characterization of milled samples showed that an amorphous system was obtained just using the combination of the drug with tryptophan (GSF-TRYP BM). At the higher dose tested (0.850 mmol L−1) during in vitro kinetic solubility studies, this amorphous system increased the AUC in FaSSGF (88.6%) and FaSSIF (58.2%) media when compared to GSF QC. Thus, the ability of this amino acid to inhibit GSF precipitation appears to be dependent on its concentration in solution and could be optimized. During the stability study, TRYP inhibited GSF recrystallization in the solid-state for a period of 12 months, whereas GSF QC recrystallized in 1 week.