This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
MAO inhibitors should not be used with: 
Select and explain. 
A. Pethidine, B. Pentazocine, C. Buprenorphine, D. Morphine
A: Pethidine
Answer: A: Pethidine 
Explanation: Pethidine should be avoided in patients receiving MAO inhibitors, because both these drugs can result in very high levels of serotonin. MAOI inhibits breakdown of serotonin and pethidine inhibits reuptake of serotonin. This result in excess excitation characterized by agiation, delirium, headache, rigidity, hyperpyrexia and coma. When both of these drugs are used together respiratory, cardiovascular depression and coma can result due to the inhibition of hepatic microsomal enzymes by MAOI, resulting in an increase in the level of pethidine. Ref: Essentials of Medical Pharmacology By KD Tripathi, 5th Edition, Page 431 - 2