Impurities in drugs II: meperidine and its formulations

Three lots of meperidine hydrochloride, seven lots of meperidine tablets, and 41 lots of meperidine injectables were examined for impurities by TLC. Impurities found were ethyl 1-benzyl-4-phenyl-4-piperidinecarboxylate, methyl-4-piperidinecarboxylate, ethyl-4-phenyl-4-piperidinecarboxylate, and three unidentified compounds. Not all impurities were found in every lot of drug investigated, and none of the impurities exceeded a concentration of 1% of the meperidine present.