Impurities in drugs III: Trihexyphenidyl

Area of Science:

• Pharmaceutical Chemistry
• Analytical Chemistry

Background:

• Trihexyphenidyl hydrochloride is a medication used to treat symptoms of Parkinson's disease.
• Ensuring the purity of pharmaceutical products is critical for patient safety and drug efficacy.

Purpose of the Study:

• To identify and quantify impurities in trihexyphenidyl hydrochloride raw material, elixir, and tablet formulations.
• To establish the presence and levels of specific chemical impurities in pharmaceutical products.

Main Methods:

• Thin-layer chromatography (TLC) was employed to examine two lots of raw material, one lot of elixir, and ten lots of tablets.
• Mass spectrometry (MS) and gas-liquid chromatography (GLC) were used to confirm the identity of detected impurities by comparing Rf values and retention times with synthesized standards.

Main Results:

• Three specific impurities were detected: 1-phenyl-2-propenone, 3-piperidinopropiophenone, and 3-aminopropiophenone.
• These impurities were not uniformly present across all examined lots.
• The concentration of any single impurity did not surpass 1.9% of the labeled drug claim in any sample.

Conclusions:

• The study successfully identified and quantified key impurities in trihexyphenidyl hydrochloride products.
• Detected impurity levels were below established safety thresholds, indicating acceptable product quality.
• The analytical methods employed (TLC, MS, GLC) are effective for impurity profiling in pharmaceutical analysis.