Which of the following is not an opioid analgesic?
Morphine
Fentanyl
Codeine
Tramadol
Tramadol is not an opioid analgesic. It is a centrally acting analgesic that works by inhibiting the reuptake of norepinephrine and serotonin.
Incorrect options:
1) Morphine is an opioid analgesic that works by binding to mu-opioid receptors in the brain and spinal cord.
2) Fentanyl is an opioid analgesic that is more potent than morphine and is used for severe pain relief.
3) Codeine is an opioid analgesic that is commonly used for mild to moderate pain relief.