Which of the following opioid analgesic acts primarily through K opioid receptors?: (A) Pentazocine, (B) Methadone, (C) Buprenorphine, (D) Pethidine
Answer is A. (Ref: KDT 6/e p464, 465) Pentazocine can cause dysphoric reactions (hallucinations) by stimulating the K receptors.