Assessment of the relevance of osmolality measurement as a criterion for the stability of solutions

Objectives

The measurement of osmolality is used by many authors as an additional stability criterion of a drug in solution. In the current state of knowledge, no scientific publication correlates the osmolality values and the stability of a solution. To study the relevance of this analytical technique by measuring the osmolality of injectable solutions whose instability has been chemically demonstrated by high performance liquid chromatography (HPLC).

Methods

Selection of 13 drug preparations whose chemical instability has been demonstrated in the literature. Realization of three identical samples per selected preparation and measurements of the osmolality of the freshly prepared solutions, then, at various storage times until a chemical degradation of the molecule validated by HPLC of at least 10% and possibly up to 40%.

Results

Measurements of the osmolality were performed on five antibiotics (amoxicillin/clavulanic acid, cefepime, cefoxitine, meropenem and temocillin and cefoxitin) and five anticancer drugs (azacitidine, bendamustine, busulfan, fotemustine and oxaliplatin). Osmolality varied from −6.30 to 11.10% for antibiotics and from 0.57 to 2.04%.

Conclusions

Among the preparations tested, only two formulations have a variation in osmolality in accordance with the chemical degradation. For the other 11 formulas, the variations in osmolality values where not correlated with the degradation measured by HPLC. In view of these results, osmolality does not seem to be a criterion of choice for the study of drug stability. In the majority of the unstable solutions studied, the variation of osmolality measurements does not correlate with the loss of concentration and the appearance of degradation products.

Clinical response and pharmacokinetics of bendamustine as a component of salvage R-B(O)AD therapy for the treatment of primary central nervous system lymphoma (PCNSL)

Background

A relatively high proportion of patients diagnosed with primary CNS lymphoma will experience recurrent disease, yet therapy options are limited in salvage therapy. This is the first study to evaluate a bendamustine-based combination regimen for the treatment of relapsed/refractory PCNSL and to characterize bendamustine pharmacokinetics in the human CSF.

Methods

Patients received bendamustine 75 mg/m² for two days as part of R-B(O)AD administered intravenously every 4 weeks for up to 4 cycles. Response and adverse events of the regimen were assessed. A sparse sampling strategy and population based modeling approach was utilized for evaluation of plasma and CSF levels of bendamustine.

Results

Ten patients were enrolled into study of whom 70% were of refractory disease and with high IELSG prognostic risk scores. The ORR of R-BOAD was 50% (95% CI, 0.24 to 0.76) with one patient achieving CR and four PR. Primary toxicity of the regimen was reversible myelosuppression, mostly grade 3 or 4 neutropenia. The C_max mean for plasma and CSF were 2669 ng/mL and 0.397 ng/mL, respectively, and patients with response at deep tumor sites displayed higher trends in peak exposure. Pharmacokinetic data was best described by a four-compartment model with first-order elimination of drug from central plasma and CSF compartments.

Conclusions

R-BOAD is an effective salvage option for PCNSL, but with significant hematologic toxicity. Bendamustine CSF levels are minimal; however correspond to plasma exposure and response.

Trial registration

ClinicalTrials.gov NCT03392714; retrospectively registered January 8, 2018.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4632-y) contains supplementary material, which is available to authorized users.

Determination of Bendamustine in Human Plasma and Urine by LC-FL Methods: Application in a Drug Monitoring

Simple and sensitive liquid chromatography (LC) methods with fluorescence (FL) detection for the determination of bendamustine (BM) in human plasma and urine were developed and validated. The procedure of BM extraction from a plasma sample involved solid-phase extraction with a C18 SPE column, while liquid–liquid extraction with dichloromethane was applied for a urine sample. In both methods, cinoxacin was used as the internal standard. Chromatographic separations were performed on a Synergi Max-RP column, while FL detector was set at the excitation wavelength of 328 nm and the emission wavelength of 420 nm. The LC-FL methods were validated for accuracy, precision, selectivity, linearity, recovery, and stability. The detection limits for BM were 0.5 and 2.5 ng mL⁻¹ in plasma and urine, respectively. The intra-day and inter-day precisions were less than 9.86 %, while the accuracies were higher than 92.63 and 94.29 % for BM in plasma and urine, respectively. The proposed LC-FL methods were sensitive, robust, and specific, allowing reliable drug quantification in plasma and urine samples. The methodologies were successfully applied to monitoring of BM in a child with cancer treated with BM.

Determination and characterization of two degradant impurities in bendamustine hydrochloride drug product

Bendamustine hydrochloride is an alkylating antitumor agent with a good efficacy in the treatment of chronic lymphocytic leukemia (CLL) and B-cell non-Hodgkin's lymphoma (B-NHL). Under the stressed conditions, two degradant impurities in bendamustine hydrochloride drug product were detected by high-performance liquid chromatography. These two degradant impurities were isolated from preparative liquid chromatography, and were further characterized using Q-TOF/MS and nuclear magnetic resonance (NMR). Based on the MS and NMR spectral data, they were characterized as 4-[5-(2-chloro-ethylamino)-1-methyl-1H-benzoimidazol-2-yl] butyric acid hydrochloride (impurity-A) and 4-{5-[[2-(4-{5-[bis-(2-chloroethyl) amino]-1-methyl-1H-benzoimidazol-2-yl}-butyryloxy)-ethyl]-(2-chloroethyl)amino]-1-methyl-3a, 7a-dihydro-1H-benzoimidazol-2-yl} butyric acid hydrochloride (impurity-B). Isolation, structural elucidation of these two impurities by spectral data (Q-TOF/MS, (1)H NMR, (13)C NMR, D2O exchange NMR and two-dimensional NMR) and the probable formation mechanism of the impurities were discussed.