Identification and quantitation of impurities in methotrexate

Area of Science:

• Pharmaceutical Chemistry
• Analytical Chemistry
• Medicinal Chemistry

Background:

• Methotrexate is a crucial chemotherapy agent used in treating various cancers and autoimmune diseases.
• Ensuring the purity of pharmaceutical compounds like methotrexate is critical for patient safety and therapeutic efficacy.
• Previous studies have identified known impurities in bulk and commercial methotrexate samples.

Purpose of the Study:

• To identify and characterize impurities present in bulk, commercial, and investigational methotrexate samples.
• To compare the impurity profiles across different batches of methotrexate.
• To assess the overall purity of methotrexate used in clinical and research settings.

Main Methods:

• High-performance liquid chromatography (HPLC) with gradient elution was employed for impurity separation.
• Diethylaminoethylcellulose (DEAE-cellulose) chromatography was utilized as the stationary phase.
• Spectroscopic techniques were used for the identification of unknown impurities (though not explicitly stated, implied by identification).

Main Results:

• Two previously unidentified impurities, 4-amino-N10-methylpteroyl-N-methylglutamine and 2,4-di-amino-N10-methylpteramide, were identified.
• A distinct impurity spectrum was observed in a new batch of methotrexate synthesized for investigational purposes.
• The purity of all analyzed methotrexate samples was determined to be approximately 80% on an anhydrous basis.

Conclusions:

• The study successfully identified novel impurities in methotrexate, contributing to a better understanding of its chemical profile.
• Variations in impurity profiles across different methotrexate batches underscore the importance of stringent quality control measures.
• The consistent ~80% purity level across samples indicates a need for improved synthesis and purification protocols for methotrexate.