A novel stability-indicating method for known and unknown impurities profiling for diltiazem hydrochloride pharmaceutical dosage form (tablets)

Background A novel gradient, high-sensitive and specific stability-indicating reverse-phase HPLC method was developed and validated for quantitative purpose of known, unknown and degradant impurities profiling for diltiazem hydrochloride tablets. The impurities were separated on the Zorbax RX C8 column (150 mm × 4.6 mm, 5 μm) with mobile phase-A consisting of a mixture of 0.05 M sodium dihydrogen phosphate monohydrate buffer pH 3.0 and methanol in the ratio 800:200v/v and mobile phase-B consisting of acetonitrile with a flow rate of 1.0 mL min−1. The column compartment was maintained at 35 °C, and the detection wavelength was 240 nm. Diltiazem hydrochloride, its known impurities and unknown impurities have been well resolved from each other. Results The linearity of the method has been demonstrated across the concentration range of 0.18 to 5.65 µg mL−1 for EP impurity-F with correlation coefficient R2 greater than 0.99. Recovery of method was proved from LOQ to 150% for known and unknown impurities with respect to test concentration and found in between 80 and 120%. Forced degradation study and specificity experiment results with mass balance proved the stability-indicating nature of the method and separated all known, unknown impurities and degradants from each other as well as from main drug component (diltiazem hydrochloride). The mass balance for stress study was found in between 95 and 105%. Conclusion Newly developed analytical method was validated as per ICH Q2 (R1) guidelines “Validation of analytical procedure” and found linear, accurate, specific, robust and precise in the established working range.

In Vitro and In Vivo Evaluation of Oral Controlled Release Formulation of BCS Class I Drug Using Polymer Matrix System

Diltiazem hydrochloride is a calcium channel blocker, which belongs to the family of benzothiazepines. It is commonly used to treat hypertension and atrial fibrillation. Even though the drug has high solubility, its high permeability and rapid metabolism in the liver can limit the bioavailability and increase the dose frequencies for up to four times per day. This study focused on a polymer matrix system not only to control the drug release but also to prolong the duration of bioavailability. The polymer matrices were prepared using different ratios of poloxamer-188, hydroxypropyl methylcellulose, and stearyl alcohol. In vitro and in vivo assessments took place using 24 rabbits and the results were compared to commercially available product Tildiem® (60 mg tablet) as reference. Overall, the rate of drug release was sustained with the gradual increase of poloxamer-188 incorporated with hydroxypropyl methylcellulose and stearyl alcohol in the matrix system, achieving a maximum release period of 10 h. The oral bioavailability and pharmacokinetic parameters of diltiazem hydrochloride incorporated in polymer matrix system were similar to commercial reference Tildiem®. In conclusion, the combination of polymers can have a substantial effect on controlling and prolonging the drug release pattern. The outcomes showed that poloxamer-188 combined with hydroxypropyl methylcellulose and stearyl alcohol is a powerful matrix system for controlling release of diltiazem hydrochloride.