Novel Validated RP-HPLC Method for Bendamustine Hydrochloride Based on Ion-pair Chromatography: Application in Determining Infusion Stability and Pharmacokinetics.

Ion pair chromatography was used for quantifying bendamustine hydrochloride (BH) in its marketed vial. The permissive objective was to investigate time duration for which highly susceptible drug content of the marketed vial remained stable after reconstitution. However, the method could also be used to measure extremely low levels of drug in rat plasma and a pharmacokinetic study was accordingly conducted to further showcase method's applicability. Optimized separation was achieved on C-18 Purospher®STAR (250 mm × 4.6 mm, 5 µm particle size) column. Mobile phase flowing at 1.5 mL/min consisted of 5 mM sodium salt of octane sulfonic acid dissolved in methanol, water and glacial acetic acid (55:45:0.075) maintained at pH 6. Detection was carried out at 233 nm with BH eluting after 7.8 min. Validation parameters were determined as per ICH guidelines. Limit of detection and limit of quantification were found to be 0.1 µg/mL and 0.33 µg/mL, respectively. The recoveries were 98-102% in bulk and 85-91% in plasma. The developed method was specific for BH, and utilized for assessing its short-term stability in physiologic solvents and forced degradation products in acid, base, oxidative, light and temperature induced stress environments.

Inclusion complexes of bendamustine with ß-CD, HP-ß-CD and Epi-ß-CD: in-vitro and in-vivo evaluation.

The objective of the present work was to investigate the inclusion behavior of bendamustine (BM) with ß-cyclodextrin and its hydrophilic derivatives (HP-ß-CD and Epi-ß-CD) for the enhancement of aqueous solubility, dissolution and bioavailability. The supramolecular binary complexes were prepared by three different methods, viz. physical mixture (PM), kneading (KND) and co-evaporation (COE). Phase-solubility study revealed the higher solubilizing and complexing ability of polymerized cyclodextrin (Ks = 645 M(-1)) than parent cyclodextrin (Ks = 43 M(-1)) and chemically derived cyclodextrin (Ks = 100 M(-1)). Meanwhile, the solubility of BM was significantly enhanced in phosphate buffer of pH 6.8, which was 24.5 folds greater compared with the phosphate buffer pH 4.5 and four times greater than aqueous medium. The dissolution efficiency was found to be highest for BM: Epi-ß-CD complex (87%) compared to BM: HP-ß-CD complex (84%), BM: ß-CD (79%) and pure drug (20%). In-vivo pharmacokinetic study revealed that the bioavailability of BM was enhanced 2.55 times on complexation with Epi-ß-CD using KND method. The t1/2 of BM was increased from 34.2 min to approximately 75.7 min, allowing the absorption for longer time. The order of increase in solubility, dissolution and bioavailability of BM was KND > COE > PM > pure drug. Thus, the strategy of host-guest inclusion was very effective and could be successfully used in the development of suitable pharmaceutical dosage form with enhanced therapeutic activity.