Viscoelastic interactions between polydeoxyribonucleotide and ophthalmic excipients.

This study investigated the interaction between polydeoxyribonucleotide (PDRN) and several ionic and nonionic isotonic agents, thickeners and a preservative that were employed as excipients in ophthalmic preparations. Interaction of each individual excipient and PDRN aqueous solution was evaluated by analyzing their rheological properties. Rheological properties of PDRN solutions were evaluated by dynamic oscillatory shear tests and values of elastic modulus (G'), viscous modulus (G″) and loss tangent (tan δ) were used to assess the relative changes in viscoelastic properties. At given concentrations, sodium chloride was found to show alteration in viscoelastic properties of PDRN solution while nonionic isotonic agents like d-glucose and d-sorbitol did not alter them. Similarly, nonionic water soluble polymers like polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) also did not interact with PDRN to alter the viscoelastic properties. However, there were changes observed when carbopol 940 was used as a thickener. Therefore, PDRN was found to interact with ionic excipients and the interactions were negligible when nonionic materials were examined, which suggests that nonionic excipients are suitable to be formulated with PDRN.

Preclinical Pharmacokinetic Evaluation of ß-Lapachone: Characteristics of Oral Bioavailability and First-Pass Metabolism in Rats.

ß-Lapachone has drawn increasing attention as an anti-inflammatory and anti-cancer drug. However, its oral bioavailability has not been yet assessed, which might be useful to develop efficient dosage forms possibly required for non-clinical and clinical studies and future market. The aim of the present study was thus to investigate pharmacokinetic properties of ß-lapachone as well as its first-pass metabolism in the liver, and small and large intestines after oral administration to measure the absolute bioavailability in rats. A sensitive HPLC method was developed to evaluate levels of ß-lapachone in plasma and organ homogenates. The drug degradation profiles were examined in plasma to assess the stability of the drug and in liver and intestinal homogenates to evaluate first-pass metabolism. Pharmacokinetic profiles were obtained after oral and intravenous administration of ß-lapachone at doses of 40 mg/kg and 1.5 mg/kg, respectively. The measured oral bioavailability of ß-lapachone was 15.5%. The considerable degradation of ß-lapachone was seen in the organ homogenates but the drug was quite stable in plasma. In conclusion, we suggest that the fairly low oral bioavailability of ß-lapachone may be resulted from the first-pass metabolic degradation of ß-lapachone in the liver, small and large intestinal tracts and its low aqueous solubility.