Pethidinic acid is a controlled drug because of its potential uses in manufacturing both pethidine itself and some of its substituted derivatives, but it has little opioid activity in its own right. Metabolism of pethidine to pethidinic acid is carried out mainly by the carboxylesterase enzyme hCE-1 in the liver, and since the activity of this enzyme can vary between individuals, the rate and extent of pethidinic acid production can vary.
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^ Zhang J, Burnell JC, Dumaual N, Bosron WF. Binding and hydrolysis of meperidine by human liver carboxylesterase hCE-1. Journal of Pharmacology and Experimental Therapeutics. 1999 Jul;290(1):314-8.
^ Wainer IW, Stambaugh JE. GLC determination of meperidinic and normeperidinic acids in urine. Journal of Pharmaceutical Sciences. 1978 Jan;67(1):116-8.
^ Odar-Cederlof I, Boreus LO, Bondesson U, Holmberg L, Heyner L. Comparison of renal excretion of pethidine (meperidine) and its metabolites in old and young patients. European Journal of Clinical Pharmacology. 1985;28(2):171-5.