Stability of diltiazem in acid solution

Area of Science:

• Pharmaceutical Chemistry
• Analytical Chemistry

Background:

• Diltiazem is a widely used calcium channel blocker.
• Understanding its stability is crucial for formulation and storage.
• Optically active drug stability studies often require precise analytical methods.

Purpose of the Study:

• To investigate the stability of diltiazem under specific thermal and pH conditions.
• To determine the rate of hydrolysis of the acetate ester moiety in diltiazem.
• To evaluate the utility of photoelectric polarimetry for stability studies.

Main Methods:

• Diltiazem solutions were incubated at 70°C across a pH range of 0.45 to 6.1.
• Polarimetry was used to monitor changes in optical activity.
• Hydrolysis rates were determined by analyzing reaction kinetics.

Main Results:

• No racemization of diltiazem was observed under the tested conditions.
• The hydrolysis rate of the acetate ester moiety was found to be slow.
• A minimum hydrolysis rate was identified around pH 3.5.
• Photoelectric polarimetry proved to be a rapid, convenient, and cost-effective method for analyzing optically active compounds.

Conclusions:

• Diltiazem exhibits good stability against racemization at 70°C within the studied pH range.
• The acetate ester hydrolysis is a slow process, with optimal stability at approximately pH 3.5.
• Photoelectric polarimetry is a highly advantageous technique for kinetic studies of optically active pharmaceutical compounds.