This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
Long term use of pethidine is avoided because a metabolite of pcthidine is associated with: 
Select and explain. 
A. Constipation, B. Dependence, C. Seizures, D. Respiratory depression
C: Seizures
Answer: C: Seizures 
Explanation: (Ref: KDT 6/e p459) Pethidine is mainly metabolized by hydrolysis to meperidinic acid but a minor pathway of metabolism involving methylation to nor-pethidine is also present. In overdose of pethidine, this minor pathway assumes impoance and there is accumulation of nor-pethidine. This compound possesses excitatory propeies and can lead to tremors, mydriasis, delirium, myoclonus and convulsions.