💊 Morphine is considered the classic opioid analgesic with which other painkillers are compared. Like other medications in this class, morphine has an affinity for delta, kappa, and mu-opioid receptors. 💊 This drug produces the majority of its analgesic effects by binding to the mu-opioid receptor within the central nervous system (CNS) and the peripheral nervous system (PNS). 💊 Morphine can potentially be a lethal medication when not used properly. It causes a host of symptoms related to depression of the CNS. Severe respiratory depression is the most feared complication of morphine in cases of overdose. Immediate injection of naloxone is required to reverse the effects of morphine.