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Author: Admin | 2025-04-28
Opioids appear to be modestly immunosuppressive.Concentration-Efficacy Relationships The minimum effective analgesic concentration will vary widely among patients, especially among patients who have been previously treated with potent agonist opioids. The minimum effective analgesic concentration of morphine for any individual patient may increase over time due to an increase in pain, the development of a new pain syndrome, and/or the development of analgesic tolerance [see Dosage and Administration (2.1, 2.3)] Concentration–Adverse Reaction Relationships There is a relationship between increasing morphine plasma concentration and increasing frequency of dose-related opioid adverse reactions such as nausea, vomiting, CNS effects, and respiratory depression. In opioid-tolerant patients, the situation may be altered by the development of tolerance to opioid-related adverse reactions [see Dosage and Administration (2.1, 2.3, 2.4)]. 12.3 Pharmacokinetics Absorption Morphine sulfate is an extended-release tablet containing morphine sulfate. Morphine is released from morphine sulfate extended-release tablets somewhat more slowly than from immediate-release oral preparations. Following oral administration of a given dose of morphine, the amount ultimately absorbed is essentially the same whether the source is morphine sulfate extended-release tablets or an immediate-release formulation. Because of pre-systemic elimination (i.e., metabolism in the gut wall and liver) only about 40% of the administered dose reaches the central compartment. The oral bioavailability of morphine is approximately 20 to 40%. When morphine sulfateis given on a fixed dosing regimen, steady-state is achieved in about a day. Food Effect The effect of food upon the systemic bioavailability of morphine sulfate has not been systematically evaluated for all strengths. One study, conducted with the 30 mg morphine sulfateextended-releasetablets, showed no significant differences in Cmax and AUC (0-24h) values, whether the tablet was taken while fasting or with a high-fat breakfast. Distribution Once absorbed, morphine is distributed to skeletal muscle, kidneys, liver, intestinal tract, lungs, spleen, and brain. Morphine also crosses
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