The Chemical Structure of Morphine

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Morphine
It is the most important pharmacologically active constituent of opium, the resin copied from the dried juice of the opium poppy. It was first established into clinical practice more than 200 years ago. It is the prototype opioid drug, whose analgesic and rewarding effects are mediated by activating opioid receptors which are found mainly within the central nervous system (CNS). Morphine continues the strong opioid of choice for moderate to severe cancer pain and it is on the World Health Organization’s important drugs list.
Cancer patients are usually unwilling to be managed with morphine as they fear its adverse effect and the risk of addiction or they have it as solely a comfort for the dying rather than a legitimate
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However, analgesic is the basic desirable effect of morphine, it used for other medicinal functions via the ages, involving as an antidiarrhoeal agent and an antitussive. Currently, it has also been used for the relief of breathlessness in both cancer and non-malignant disease. There are some factors that effect on pharmacodynamics of morphine such as genetic and environmental factors.
Pharmacokinetics
Absorption
Oral morphine absorption happens predominantly in the alkaline of the upper small intestine and is more or less complete absorption. Absorption in the stomach is poor as stomach is acidic environment, while morphine is weak base. Oral bioavailability is about 33% in the systematic circulation. Onset of action of oral morphine is 20-30 min and duration of action is 3-6 hours. Furthermore, plasma concentration is usually achieved at 3-6 hours with an attenuated peak and longer half life is maintained over 12-24 h.
Spinal absorption
Morphine is administered epidurally or intrathecally which is not rapidly absorbed into systematic circulation due to its relatively hydrophilic. This probably led to long half life in cerebral fluid (CSF) 90-120 min and widespread rostral redistribution.
Elimination
Half-life: it depends on the route of administration; it is about 1.5-4.5 hours for oral and 1.5 hours for intravenous
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