Morphine Pharmacology - PM 719 Spring 2025 - PDF

PM 719 Pharmacology II Seven Things Document Spring 2025 Chapter 31 Opioids **Morphine** \(1) Drug Class and Stem: Morphine is one of the three major drugs obtained from the opium (poppy) plant, morphine, codeine (methyl morphine), and thebaine. Smoking or ingesting opium is simply a way to ge...

PM 719 Pharmacology II Seven Things Document Spring 2025 Chapter 31 Opioids **Morphine** \(1) Drug Class and Stem: Morphine is one of the three major drugs obtained from the opium (poppy) plant, morphine, codeine (methyl morphine), and thebaine. Smoking or ingesting opium is simply a way to get morphine into the body. Morphine was isolated from opium in 1820, no stem. \(2) Primary Clinical Use: Morphine is the gold standard for analgesic drugs against which all other drugs are compared. \(3) Site of Action and Receptor(s): Morphine is a full agonist at mu-opioid receptors and produces its biological effects mostly through its binding to mu receptors. \(4) Mechanism of Action: Morphine binds to mu receptors (and to a lesser extent the kappa and delta receptors) and promote analgesia. The main action is inhibition of the pain signal, the pain signal arrives in the brain but the brain cannot process the signal. \(5) Physiological Effects: Morphine biotransformed by Phase II glucurondation and eliminated by the kidney. Dose adjustment required for reduced kidney function (CC and eGFR) Euphoria, analgesia, sedation, are common ADRs Tolerance develops (higher doses required to achieve the same degree of analgesia), physical dependance soon follows. The long term use of morphine for pain management can result in opioid induced hyperalgesia (increase sensation of pain). \(a) CNS: analgesia, euphoria, sedation and respiratory depression, cough suppression, miosis, truncal rigidity, nausea and vomiting. \(b) PNS: bradycardia, constipation, depressed renal function, pruritis (flushing, itching), \(6) Major ADRs: Addiction, truncal rigidity, reparatory depression (the usual cause of death), Some morphine metabolites are highly bioactive and rapidly eliminated by the normal kidney. Impaired kidneys cannot remove these bioactive metabolites and their buildup can lead to respiratory depression and death even from a normal therapeutic dose. Overdoses are treated with IM or intranasal opioid antagonist such as naloxone. \(7) Modes of Administration: PO, IM, IV, SC, skin patches and rectal suppositories are used. Morphine PO shows very high first pass effect, a larger dose than parenteral is required for PO dosing (30 mg) vs parenteral dosing (10 mg.) Patient Controlled Analgesia (PCA), whereby the patient self-administers a dose of morphine at the push of a button on a drug pump attached to the IV set.