Drug interactions with potential rubber closure extractables. Identification of thiol-disulfide exchange reaction products of captopril and thiurams.

Mixtures of thiuram disulfides are frequently used as accelerators in rubber stoppers for injectables and sterilized powders for injection. Rapid reactions of thiuram disulfides between themselves and with thiols yield mixed disulfides due to thiol-disulfide exchange. The possibility of exchange reactions of thiuram disulfides extracted from rubber stoppers and drug products containing pendant thiol groups have not been reported in the analysis of potential stopper extractables. In this paper we report the formation and identification of mixed thiuram disulfides of N,N,N',N'-dimethylthiuram disulfide (TMTD), N,N,N',N'-dibutylthiuram disulfide (TBTD), and captopril (a thiol-containing drug). A reversed-phase HPLC method was developed for the determination of TMTD, TBTD, captopril and their disulfides in aqueous vehicles, using a YMC ODS AQ column at 35 degrees C and mobile phases A and B consisting of acetonitrile:water:trifluoroacetic acid (TFA) (20:80:0.1) and acetonitrile:TFA (100:0.1), respectively. The captopril-TBTD and captopril-TMTD disulfides were identified by MS, with molecular ions at m/z 420.9 and m/z of 337.1, respectively. Possible structures for the fragment ions in the spectra are provided. Mixed captopril-thiuram formation was studied as a function of pH. Captopril-TMTD formation was enhanced at pH 6.0, reaching a maximum of 31.3% in 4.1h. At pH 4.0 and 2.2, the mixed captopril adduct product was still detected in solution after 20h. The impact of the formation of mixed disulfide products of thiol-containing drugs with thiurams in the HPLC profile of extractables and leachables studies is discussed.

Identification and control of a degradation product in Avapro film-coated tablet: low dose formulation.

A degradation product was formed during the long-term stability studies (LTSS) of the low dose formulation of Avapro film-coated tablet. The degradant was identified as the hydroxymethyl derivative (formaldehyde adduct) of the drug substance, irbesartan, based upon analysis with LC/MS, LC/MS/MS, and chromatographic comparison to the synthetic hydroxymethyl degradation product. Laboratory studies demonstrated that the interaction of individual excipients with the drug substance at elevated temperature and polyethylene glycol (PEG) used in the coating material, Opadry II White, leads to the generation of this formaldehyde adduct. Spiking of formaldehyde to the solution of drug substance gradually produced this impurity and the kinetics studies demonstrated that the reaction between formaldehyde and irbesartan is a second order reaction with a rate constant of 2.6 x 10(-4) M(-1)min(-1) at 25 degrees C in an aqueous media. The redevelopment of the formulation by eliminating PEG from the Opadry II White dry-blend system was enabled by understanding the formaldehyde adduct formation.

Separation of atropisomers by chiral liquid chromatography and thermodynamic analysis of separation mechanism.

In the pharmaceutical industry, the analysis of atropisomers is of considerable interest from a scientific and regulatory perspective. The compound of interest contains two stereogenic axes due to the hindered rotation around the single bonds connecting the aryl groups, which results in four potential configurational isomers (atropisomers). The separation of the four atropisomers is achieved on a derivatized ß-cyclodextrin bonded stationary phase. Further investigation shows that low temperature conditions, including sample preparation (-70 °C), sample storage (-70 °C), and chromatographic separation (6 °C), were critical to preventing interconversion. LC-UV-Laser Polarimetric analysis identified peak 1/2 as a pair of enantiomers and peak 3/4 as another. Thermodynamic analysis of the retention data indicated that the separation of the pairs of enantiomers is primarily enthalpy controlled as indicated by the positive slope of the van't Huff plot. The difference in absolute Δ (Δ H), ranged from 2.20 kJ/mol to 2.42 kJ/mol.

Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations.

Ion-pairing high-performance liquid chromatography-ultraviolet (HPLC-UV) methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid (EDTA) in Abilify® (a small molecule drug with aripiprazole as the active pharmaceutical ingredient) oral solution and diethylenetriaminepentaacetic acid (DTPA) in Yervoy® (a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient) intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions (Cu2+, Fe3+) which generate highly stable metallocomplexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation involving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the determination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids (APCAs) including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.