Changes in recovery due to drug product matrix ageing as a source of mass imbalances.

An important quality feature of stability testing of drug products is mass balance. Besides several known or anticipated causes for mass imbalances, a further potential cause that has not yet been systematically assessed might be incomplete recovery due to the influence of matrix ageing. The genotoxic degradation product 4-chloroaniline (PCA) and the unstable drug substance estradiol (E2) that is known to be difficult to extract from matrices in low-dose solid formulations were chosen as examples. A marketed product containing E2 as well as two marketed products that potentially contain PCA were investigated together with experimental formulations containing E2 or PCA that were produced for this study. To accelerate drug product matrix ageing, samples were stored at different conditions for defined storage periods. PCA and E2 recovery was determined at all sampling time points, respectively. In comparison to unstressed samples, significant changes in recovery were observed in 67% of the formulations investigated. Consequently, the outlined procedure can be regarded as a promising approach to reveal potential reasons for mass imbalance.

Investigating the stability of the nonionic surfactants tocopheryl polyethylene glycol succinate and sucrose laurate by HPLC-MS, DAD, and CAD.

High-performance liquid chromatography (HPLC) methods using a charged aerosol detector (CAD), a mass selective detector (MSD), and a diode array detector (DAD) were developed to characterize the nonionic surfactants d-α-tocopheryl polyethylene glycol (1000) succinate (TPGS) and Surfhope sugar ester D-1216 (sucrose laurate). The molecular structure and the heterogeneous composition resulting from different isomers and various lengths of polyethylene glycol (PEG) chains make it difficult to develop sensitive and specific analytical methods for both surfactants. Hence, there is lack of knowledge about the stability and grade of impurity of these compounds. Sucrose laurate does not possess any chromophore, thus UV detection is not applicable. Therefore, CAD and MSD have been used for determination. The aim of the study was to characterize these nonionic surfactants and to examine chemical stability at pH 1.0 and 37 °C, simulating harsh gastric conditions. It was shown that both compounds are liable to degradation under these conditions. Sucrose monolaurate exhibited a massive degradation within 8 h incubation due to cleavage of the glycosidic bondage. About 50% of sucrose monolaurate broke down, whereas a marginal amount of 3.4% (± 0.4%) of TPGS degraded into d-α-tocopheryl succinate and the associated PEG chain.

Volume to dissolve applied dose (VDAD) and apparent dissolution rate (ADR): tools to predict in vivo bioavailability from orally applied drug suspensions.

Low solubility of drug candidates generated in research contributes to their elimination during subsequent development due to insufficient oral bioavailability (BA) of crystalline compound. Therefore, the purpose of the study was to identify critical in vitro solubility and dissolution parameter that would predict critical in vivo dissolution by means of in vitro-in vivo correlation. Thermodynamic solubility and apparent dissolution rate (ADR) were determined using the shake-flask method and mini-flow-through-cell, respectively. Oral BA studies in rats and humans were conducted from drug solution and suspension/tablets. Relative BA was calculated using F(rel) [%]=AUC(suspension)/AUC(solution)*100, representing a measure of in vivo dissolution. Roughly, F(rel) rat >50% translates into F(rel) human of >90%. Both, ADR and log volume to dissolve applied dose (VDAD), when plotted against F(rel) rat, revealed certain threshold levels, (ADR, ∼150-200 µg of compound dissolved under respective assay conditions; VDAD, ∼100-500 ml/kg) which translate into F(rel) in rats of >50%. Thus, assuming that F(rel)>50% in rats is indicative of sufficient in vivo dissolution in humans after oral application, drugs should exhibit a VDAD of ∼100-500 ml/kg or less in aqueous media to avoid insufficient or varying drug absorption.

Effects of non-ionic surfactants on cytochrome P450-mediated metabolism in vitro.

The purpose of the study was to investigate the impact of commonly used non-ionic surfactants on cytochrome P450 (CYP) 3A4-mediated metabolism of testosterone and the CYP2C9-mediated metabolism of diclofenac. Polysorbate 80 (PS 80), D-α-tocopheryl polyethylene glycol (1000) succinate (TPGS), sucrose laurate, Cremophor EL (CR EL), and Cremophor RH 40 (Cr RH 40) were incubated with human liver microsomes at different concentrations to determine the IC(50) of the reduced metabolism of the model substrates. Inhibitory potential in case of all tested compounds could be observed already below their critical micelle concentrations (CMC) and in concentration-dependant manner. The IC(50) of the CYP 3A4-mediated 6ß-hydroxylation of testosterone has been determined as 0.40 mM (PS 80), 0.15 mM (TPGS), 0.20mM (sucrose laurate), 0.60mM (CrEL), and 0.80 mM (CrRH40). The IC(50) concerning the CYP 2C9-mediated 4-hydroxylation of diclofenac has been calculated to be 0.04 mM (PS80), 0.30 mM (TPGS), 0.07 mM (sucrose laurate), 0.03 mM (CrEL), and 0.03 mM (Cr RH 40). The results indicate that these non-ionic surfactants are in vitro inhibitors of CYP-mediated metabolism and might have the potential to modify the pharmacokinetics of co-administered drugs, which are substrates of CYP, and thereby enhance their bioavailability.

Effects of non-ionic surfactants on in vitro triglyceride digestion and their susceptibility to digestion by pancreatic enzymes.

The formation of lipid digestion products is a relevant parameter for effective in vivo performance of self-emulsifying drug delivery systems (SEDDS). These lipid-based formulations contain non-ionic surfactants, therefore the effects of polysorbate 80 (PS 80), D-alpha-tocopheryl polyethylene glycol (1000) succinate (TPGS), Surfhope((R)) sugar ester D-1216 (sucrose laurate), Cremophor EL (Cr EL) and Cremophor RH 40 (Cr RH 40) on triglyceride digestion by pancreatic lipases were tested in vitro using olive oil as model substrate. The IC(50) determined are 0.13mM (PS 80), 0.08mM (TPGS), 0.46mM (sucrose laurate), 0.19mM (Cr EL) and 0.04mM (Cr RH 40). The extent of inhibitory action is ranked in downward order: Cremophor RH 40>TPGS>polysorbate 80>Cremophor EL>sucrose laurate. The effects already occur below the critical micelle concentrations (CMC) of the detergents. At low concentrations of polysorbate 80 the inhibition shows a competitive mechanism. Furthermore, degradation by pancreatic enzymes of the surfactants themselves had been tested which also can affect the solubilization capacity of the intestinal fluid after administration of a SEDDS. Polysorbate 80, Cremophor EL and Cremophor RH 40 were shown to be susceptible to digestion by pancreatic enzymes. Fatty acid esters of polysorbate 80 were hydrolyzed with an extent of 14% (+/-1.0%). 14.4% (+/-3.3%) in case of Cremophor EL had been hydrolyzed, whereas Cremophor RH 40 had been degraded to a lower extend of 6.1% (+/-2.8%). TPGS and sucrose laurate appeared to be stable in present of pancreatic enzymes.