Morphine Sulfate Injection - Scientific Information
|Manufacture:||Fresenius Kabi USA, LLC|
|Condition:||Chronic Pain, Pain|
|Form:||Liquid solution, Intramuscular (IM), Intravenous (IV)|
Morphine sulfate, an opioid agonist, is a fine white powder. When exposed to air it gradually loses water of hydration, and darkens on prolonged exposure to light. It is soluble in water and ethanol at room temperature. It is chemically designated as 7,8 -Didehydro-4,5-epoxy-17-methyl-(5α,6α)-morphinan-3,6diol sulfate (2: 1) (salt), pentahydrate, with the following structural formula:
(C17H19NO3)2 • H2SO4 • 5H2O Molecular Weight is 758.83
Morphine Sulfate Injection, USP is a sterile, nonpyrogenic solution of Morphine Sulfate Injection, USP, free of antioxidants and preservatives.
Each 1 mL syringe contains 2 mg, 4 mg, 5 mg, 8 mg or 10 mg of Morphine Sulfate, USP in 1 mL total volume with the following inactive ingredients: for the 2 mg/mL and 4 mg/mL, 8.4 mg sodium chloride, 2.3 mg of sodium citrate, 0.74 mg of citric acid, 0.111 mg of edetate disodium, 0.053 mg of calcium chloride and water for injection. For the 5 mg/mL, 8 mg/mL and 10 mg/mL, 7.5 mg sodium chloride, 3.45 mg of sodium citrate, 1.11 mg of citric acid, 0.111 mg of edetate disodium, 0.053 mg of calcium chloride and water for injection.
Mechanism of Action
Morphine, a full opioid agonist, is relatively selective for the mμ receptor, although it can interact with other opioid receptors at higher doses. In addition to analgesia, the widely diverse effects of morphine sulfate include drowsiness, changes in mood, respiratory depression, decreased gastrointestinal motility, nausea, vomiting, and alterations of the endocrine and autonomic nervous system.
Morphine concentrations are not predictive of analgesic response, especially in patients previously treated with opioids. The minimum effective concentration varies widely and is influenced by a variety of factors, including the extent of previous opioid use, age and general medical condition. Effective doses in tolerant patients may be significantly higher than in opioid-naïve patients.
Onset of analgesia occurs with 5-20 minutes following intramuscular administration of morphine, rising to peak analgesia sixty minutes after a single intramuscular injection. The duration of analgesia after a single injection is usually three to four hours. Morphine and similar opioid analgesics rapidly induce tolerance to their effects, so that the duration of analgesia may be shorter following subsequent doses of morphine. Once patients are started on morphine, the dose required for satisfactory analgesia will rise, with the rate of development of tolerance varying depending on the patient's prior narcotic use, level of pain, degree of anxiety, use of other CNS active drugs, circulatory status, total dose and the inter-dose interval.
Effects on the Central Nervous System (CNS)
The principle therapeutic action of morphine is analgesia. Although the precise mechanism of the analgesic action is unknown, specific CNS opiate receptors and endogenous compounds with morphine-like activity have been identified throughout the brain and spinal cord and are likely to play a role in the expression and perception of analgesic effects. In common with other opioids, morphine causes respiratory depression, in part by a direct effect on the brainstem respiratory centers. Morphine and related opioids depress the cough reflex by direct effect on the cough center in the medulla. Morphine causes miosis, even in total darkness.
Effects on the Gastrointestinal Tract and on Other Smooth Muscle
Gastric, biliary and pancreatic secretions are decreased by morphine. Morphine causes a reduction in motility and is associated with an increase in tone in the antrum of the stomach duodenum. Digestion of food in the small intestine is delayed and propulsive contractions are decreased. Propulsive peristaltic waves in the colon are decreased, while tone is increased to the point of spasm. The end result may be constipation. Morphine can cause a marked increase in biliary tract pressure as a result of spasm of the sphincter of Oddi. Morphine may also cause spasm of the sphincter of the urinary bladder.
Effects of the Cardiovascular System
In therapeutic doses, morphine does not usually exert major effects on the cardiovascular system. Morphine produces peripheral vasodilation which may result in orthostatic hypotension and fainting. Release of histamine can occur, which may play a role in opioid-induced hypotension. Manifestations of histamine release and/or peripheral vasodilation may include pruritus, flushing, red eyes and sweating.
Opioid agonists have been shown to have a variety of effects on the secretion of hormones. Opioids inhibit the secretion of ACTH, cortisol and luteinizing hormones (LH) in humans. They also stimulate prolactin, growth hormone (GH) secretion and pancreatic secretion of insulin and glucagon in humans and other species, rats and dogs. Thyroid stimulating hormone (TSH) has been shown to be both inhibited and simulated by opioids.
Opioids have been shown to have a variety of effects on components of the immune system in in vitro and animal models. The clinical significance of these findings is unknown.
Morphine has an apparent volume of distribution ranging from 1.0 to 4.7 L/kg after intravenous dosage. Protein binding is low, about 36%, and muscle tissue binding is reported as 54%. A blood-brain barrier exists, and when morphine is introduced outside of the CNS (e.g., intravenously), plasma concentrations of morphine remain higher than the corresponding CSF morphine levels.
Average peak morphine plasma levels of 67.4 ± 22.5 ng/mL were noted around 5 to 30 minutes following intramuscular injection of 10 mg morphine sulfate from a prefilled syringe.
Morphine has a total plasma clearance which ranges from 0.9 to 1.2 L/kg/h (liters/kilogram/hour) in postoperative patients, but shows considerable interindividual variation. The major pathway of clearance is hepatic glucuronidation to morphine -3-glucuronide, which is pharmacologically inactive. The major excretion path of the conjugate is through the kidneys, with about 10% in the feces. Morphine is also eliminated by the kidneys, 2 to 12% being excreted unchanged in the urine. Terminal half-life is commonly reported to vary from 1.5 to 4.5 hours, although the longer half-lives were obtained when morphine levels were monitored over protracted periods with very sensitive radioimmunoassay methods. The accepted elimination half-life in normal subjects is 1.5 to 2 hours.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Studies in animals to evaluate the carcinogenic potential of morphine have not been conducted.
No formal studies to assess the mutagenic potential of morphine have been conducted. In the published literature, morphine was found to be mutagenic in vitro increasing DNA fragmentation in human T- cells. Morphine was also reported to be mutagenic in the in vivo mouse micronucleus assay and positive for the induction of chromosomal aberrations in mouse spermatids and murine lymphocytes. Mechanistic studies suggest that the in vivo clastogenic effects reported with morphine in mice may be related to increases in glucocorticoid levels produced by morphine in these species. In contrast to the above positive findings, in vitro studies in the literature have also shown that morphine did not induce chromosomal aberrations in human leukocytes or translocations or lethal mutations in Drosophila.
Impairment of Fertility
No formal nonclinical studies to assess the potential of morphine to impair fertility have been conducted. Several nonclinical studies from the literature have demonstrated adverse effects on male fertility in the rat from exposure to morphine. One study in which male rats were administered morphine sulfate subcutaneously prior to mating (up to 30 mg/kg twice daily) and during mating (20 mg/kg twice daily) with untreated females, a number of adverse reproductive effects including reduction in total pregnancies, higher incidence of pseudopregnancies and reduction in implantation sites were seen. Studies from the literature have also reported changes in hormonal levels (i.e. testosterone, luteinizing hormone, serum corticosterone) following treatment with morphine. These changes may be associated with the reported effects on fertility in the rat.