Effect of a non-methoxylated N-trimethyl chitosan chloride derivative over capreomycin sulfate permeability in CaCo-2 cell monolayers

The effect of N-trimethylchitosan chloride on the intestinal permeability of capreomycin sulfate, a polypeptide antibiotic, using an in vitro model, was evaluated. To improve the mucoadhesivity and permeation enhancer properties of N-trimethylchitosan chloride, it was used a synthetic pathway that selectively alkylated the amino groups and not the hydroxyl groups in carbons 3 and 6, which decreases the potency of the polymer, leading to use higher quantities and limit its potential as a functional excipient. This non-methoxylated derivative of the studied polymer reduced in a reversible way the transepithelial electrical resistance of CaCo-2 monolayers at concentrations not higher than 0.003 % w/v, indicating that the absence of steric hindrance from methoxyl groups improves the effect of N-trimethylchitosan chloride, but at expense of a narrow range of action and higher cytotoxicity. The results of in vitro permeation studies conducted in bicameral Transwell® systems suggested that the permeability of capreomycin sulfate is low, although it was not established if the transport is exclusively paracellular or membrane transporters are involved. By using increasing concentrations of the polymer in the range of 0.001 - 0.003% w/v, it was observed a slight increase in the transport of capreomycin. Therefore, it was concluded that further studies should use N-trimethylchitosan chloride with a lower degree of quaternization or controlled methoxylation, in order to increase the mass to use and obtain a product that is able to remain retained in the intestinal lumen and which in turn interacts with the epithelium.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Inclusion complex of the antiviral drug acyclovir with cyclodextrin in aqueous solution and in solid phase

Complexation between acyclovir (ACV), an antiviral drug used for the treatment of herpes simplex virus infection, and beta-cyclodextrin (beta-CD) was studied in solution and in solid states. Complexation in solution was evaluated using solubility studies and nuclear magnetic resonance spectroscopy (¹H-NMR). In the solid state, X-ray diffraction, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dissolution studies were used. Solubility studies suggested the existence of a 1:1 complex between ACV and beta-CD. ¹H-NMR spectroscopy studies showed that the complex formed occurs with a stoichiometry ratio of 1:1. Powder X-ray diffraction indicated that ACV exists in a semicrystalline state in the complexed form with beta-CD. DSC studies showed the existence of a complex of ACV with beta-CD. The TGA studies confirmed the DSC results of the complex. Solubility of ACV in solid complexes was studied by the dissolution method and it was found to be much more soluble than the uncomplexed drug

Determination of the Dissolution/Permeation and Apparent Solubility for Microencapsulated Emamectin Benzoate Using In Vitro and Ex Vivo Salmo salar Intestine Membranes

In this work, two microencapsulation techniques were used to protect and improve the absorption of emamectin benzoate (EB), which is an antiparasitic drug used to control Caligus rogercresseyi. EB has a low aqueous solubility, which affects its absorption in the intestine of Salmo salar. Microparticles were produced by spray drying and ionic gelation, using Soluplus® (EB–SOL) and sodium alginate (EB–ALG) as polymers, respectively. Studies were conducted on dissolution/permeation, apparent permeability (Papp), apparent solubility (Sapp), and absorption using synthetic and biological membranes. Based on these results, the amount of EB in the microparticles needed to achieve a therapeutic dose was estimated. The EB–ALG microparticles outperformed both EB–SOL and free EB, for all parameters analyzed. The results show values of 0.45 mg/mL (80.2%) for dissolution/permeation, a Papp of 6.2 mg/mL in RS–L, an absorption of 7.3% in RS, and a Sapp of 53.1% in EM medium. The EB–ALG microparticles decrease the therapeutic dose necessary to control the parasite, with values of 3.0−2 mg/mL and 1.1−2 mg/mL for EB in EM and RS, respectively. The Korsmeyer–Peppas kinetic model was the best model to fit the EB–ALG and EB–SOL dissolution/permeation experiments. In addition, some of our experimental results using synthetic membranes are similar to those obtained with biological membranes, which suggests that, for some parameters, it is possible to replace biological membranes with synthetic membranes. The encapsulation of EB by ionic gelation shows it is a promising formulation to increase the absorption of the poorly soluble drug. In contrast, the spray-dried microparticles produced using Soluplus® result in even less dissolution/permeation than free EB, so the technique cannot be used to improve the solubility of EB