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Morphine - Wikipedia, the free encyclopedia


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11/17/2014
05:08 | Author: Alex Watson

Morphine
Morphine - Wikipedia, the free encyclopedia

In advanced stages of withdrawal, ultrasonographic evidence of pancreatitis has been demonstrated in some patients and is presumably attributed to spasm of the pancreatic sphincter of Oddi.

Further studies on the effects of morphine on the immune system have shown that morphine influences the production of neutrophils and other cytokines. Since cytokines are produced as part of the immediate immunological response ( inflammation ), it has been suggested that they may also influence pain. In this way, cytokines may be a logical target for analgesic development. Recently, one study has used an animal model (hind-paw incision) to observe the effects of morphine administration on the acute immunological response. Following hind-paw incision, pain thresholds and cytokine production were measured. Normally, cytokine production in and around the wounded area increases in order to fight infection and control healing (and, possibly, to control pain), but pre-incisional morphine administration (0.1-10.0 mg/kg) reduced the number of cytokines found around the wound in a dose-dependent manner. The authors suggest that morphine administration in the acute post-injury period may reduce resistance to infection and may impair the healing of the wound.

Clinical studies consistently conclude that, like other opioids, morphine often causes hypogonadism and hormone imbalances in chronic users of both genders. This side effect is dose-dependent and occurs in both therapeutic and recreational users. Morphine can interfere with menstruation in women by suppressing levels of luteinizing hormone (LH). Many studies suggest that the majority (perhaps as much as 90%) of chronic opioid users have opioid-induced hypogonadism. This effect may cause the increased likelihood of osteoporosis and bone fracture observed in chronic morphine users. Studies suggest that the effect is temporary. As of 2013, the effect of low-dose or acute use of morphine on the endocrine system is unclear.

Morphine is a potentially highly addictive substance. It can cause psychological dependence and physical dependence as well as tolerance. In the presence of pain and the other disorders for which morphine is indicated, a combination of psychological and physiological factors tend to prevent true addiction from developing, although physical dependence and tolerance will develop with protracted opioid therapy.

Although it has previously been thought that morphine was contraindicated in acute pancreatitis, a review of the literature shows no evidence for this.

The effects of morphine can be countered with opioid antagonists such as naloxone and naltrexone ; the development of tolerance to morphine may be inhibited by NMDA antagonists such as ketamine or dextromethorphan. The rotation of morphine with chemically dissimilar opioids in the long-term treatment of pain will slow down the growth of tolerance in the longer run, particularly agents known to have significantly incomplete cross-tolerance with morphine such as levorphanol, ketobemidone, piritramide, and methadone and its derivatives; all of these drugs also have NMDA antagonist properties. It is believed that the strong opioid with the most incomplete cross-tolerance with morphine is either methadone or dextromoramide.

Like loperamide and other opioids, morphine acts on the myenteric plexus in the intestinal tract, reducing gut motility, causing constipation. The gastrointestinal effects of morphine are mediated primarily by μ-opioid receptors in the bowel. By inhibiting gastric emptying and reducing propulsive peristalsis of the intestine, morphine decreases the rate of intestinal transit. Reduction in gut secretion and increased intestinal fluid absorption also contribute to the constipating effect. Opioids also may act on the gut indirectly through tonic gut spasms after inhibition of nitric oxide generation. This effect was shown in animals when a nitric oxide precursor, L-Arginine, reversed morphine-induced changes in gut motility.

Endogenous opioids include endorphins, enkephalins, dynorphins, and even morphine itself. Morphine appears to mimic endorphins. Endorphins, a contraction of the term endogenous morphines, are responsible for analgesia (reducing pain), causing sleepiness, and feelings of pleasure. They can be released in response to pain, strenuous exercise, orgasm, or excitement.

The psychological dependence associated with morphine addiction is complex and protracted. Long after the physical need for morphine has passed, the addict will usually continue to think and talk about the use of morphine (or other drugs) and feel strange or overwhelmed coping with daily activities without being under the influence of morphine. Psychological withdrawal from morphine is usually a very long and painful process. Addicts often suffer severe depression, anxiety, insomnia, mood swings, amnesia (forgetfulness), low self-esteem, confusion, paranoia, and other psychological disorders. Without intervention, the syndrome will run its course, and most of the overt physical symptoms will disappear within 7 to 10 days including psychological dependence. There is a high probability that relapse will occur after morphine withdrawal when neither the physical environment nor the behavioral motivators that contributed to the abuse have been altered. Testimony to morphine's addictive and reinforcing nature is its relapse rate. Abusers of morphine (and heroin) have one of the highest relapse rates among all drug users, ranging up to 98 per cent in the estimation of some medical experts.

The withdrawal symptoms associated with morphine addiction are usually experienced shortly before the time of the next scheduled dose, sometimes within as early as a few hours (usually between 6–12 hours) after the last administration. Early symptoms include watery eyes, insomnia, diarrhea, runny nose, yawning, dysphoria, sweating and in some cases a strong drug craving. Severe headache, restlessness, irritability, loss of appetite, body aches, severe abdominal pain, nausea and vomiting, tremors, and even stronger and more intense drug craving appear as the ome progresses. Severe depression and vomiting are very common. During the acute withdrawal period, systolic and diastolic blood pressure increase, usually beyond pre-morphine levels, and heart rate increases, which have potential to cause a heart attack, blood clot, or stroke.

Morphine was first isolated in 1804 by Friedrich Sertürner, which is generally believed to be the first ever isolation of a natural plant alkaloid in history. Sertürner began distributing it in 1817, and Merck began marketing it commercially in 1827. At the time, Merck was a single small chemists' shop. Morphine was more widely used after the invention of the hypodermic needle in 1857. Sertürner originally named the substance morphium after the Greek god of dreams, Morpheus ( Greek : Μορφεύς ), for its tendency to cause sleep. It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.

Acute morphine withdrawal, along with that of any other opioid, proceeds through a number of stages. Other opioids differ in the intensity and length of each, and weak opioids and mixed agonist-antagonists may have acute withdrawal syndromes that do not reach the highest level. As commonly cited, they are:

Studies have shown that morphine can alter the expression of a number of genes. A single injection of morphine has been shown to alter the expression of two major groups of genes, for proteins involved in mitochondrial respiration and for cytoskeleton -related proteins.

Other studies, such as the Rat Park experiments, suggest that morphine is less physically addictive than others suggest, and most studies on morphine addiction show that "severely distressed animals, like severely distressed people, will relieve their distress pharmacologically if they can." In these studies, rats with a morphine "addiction" overcome their addiction when placed in decent living environments with enough space, good food, companionship, areas for exercise, and areas for privacy. More recent research has shown that an enriched environment may decrease morphine addiction in mice.

Morphine has long been known to act on receptors expressed on cells of the central nervous system resulting in pain relief and analgesia. In the 1970s and '80s, evidence suggesting that opiate drug addicts show increased risk of infection (such as increased pneumonia, tuberculosis, and HIV ) led scientists to believe that morphine may also affect the immune system. This possibility increased interest in the effect of chronic morphine use on the immune system.

Morphine has a high potential for addiction ; tolerance and psychological dependence develop rapidly, although physiological dependence may take several months to develop. Tolerance to respiratory depression and euphoria develops more rapidly than tolerance to analgesia, and many chronic pain patients are therefore maintained on a stable dose for years. However, its effects can also reverse fairly rapidly, worsening pain through hyperalgesia.

The first step of determining that morphine may affect the immune system was to establish that the opiate receptors known to be expressed on cells of the central nervous system are also expressed on cells of the immune system. One study successfully showed that dendritic cells, part of the innate immune system, display opiate receptors. Dendritic cells are responsible for producing cytokines, which are the tools for communication in the immune system. This same study showed that dendritic cells chronically treated with morphine during their differentiation produce more interleukin-12 (IL-12), a cytokine responsible for promoting the proliferation, growth, and differentiation of T-cells (another cell of the adaptive immune system) and less interleukin-10 (IL-10), a cytokine responsible for promoting a B-cell immune response (B cells produce antibodies to fight off infection).

A large overdose can cause asphyxia and death by respiratory depression if the person does not receive medical attention immediay. Overdose treatment includes the administration of naloxone. The latter compley reverses morphine's effects, but precipitates immediate onset of withdrawal in opiate-addicted subjects. Multiple doses may be needed.

Chills or cold flashes with goose bumps ("cold turkey") alternating with flushing (hot flashes), kicking movements of the legs ("kicking the habit" ) and excessive sweating are also characteristic symptoms. Severe pains in the bones and muscles of the back and extremities occur, as do muscle spasms. At any point during this process, a suitable narcotic can be administered that will dramatically reverse the withdrawal symptoms. Major withdrawal symptoms peak between 48 and 96 hours after the last dose and subside after about 8 to 12 days. Sudden withdrawal by heavily dependent users who are in poor health is very rarely fatal. Morphine withdrawal is considered less dangerous than alcohol, barbiturate, or benzodiazepine withdrawal.

Morphine is a phenanthrene opioid receptor agonist – its main effect is binding to and activating the μ-opioid receptors in the central nervous system. In clinical settings, morphine exerts its principal pharmacological effect on the central nervous system and gastrointestinal tract. Its primary actions of therapeutic value are analgesia and sedation. Activation of the μ-opioid receptors is associated with analgesia, sedation, euphoria, physical dependence, and respiratory depression. Morphine is a rapid-acting narcotic, and it is known to bind very strongly to the μ-opioid receptors, and for this reason, it often has a higher incidence of euphoria/dysphoria, respiratory depression, sedation, pruritus, tolerance, and physical and psychological dependence when compared to other opioids at equianalgesic doses. Morphine is also a κ-opioid and δ-opioid receptor agonist, κ-opioid's action is associated with spinal analgesia, miosis (pinpoint pupils) and psychotomimetic effects. δ-opioid is thought to play a role in analgesia. Although morphine does not bind to the σ-receptor, it has been shown that σ-agonists, such as (+)- pentazocine, inhibit morphine analgesia, and σ-antagonists enhance morphine analgesia, suggesting some interaction between morphine and the σ-opioid receptor.

Its duration of analgesia is about 3–4 hours when administered via the intravenous, subcutaneous, or intramuscular route and 3–6 hours when given by mouth. Morphine is also used in slow release formulations for opiate substitution therapy (OST) in Austria, Bulgaria, and Slovenia, for addicts who cannot tolerate the side effects of using either methadone or buprenorphine, or for addicts who are "not held" by buprenorphine or methadone. It is used for OST in many parts of Europe although on a limited basis.

Morphine is the prototype narcotic drug and is the standard against which all other opioids are tested. It interacts predominantly with the μ–δ-opioid receptor heteromer. The μ-binding sites are discrey distributed in the human brain, with high densities in the posterior amygdala, hypothalamus, thalamus, nucleus caudatus, putamen, and certain cortical areas. They are also found on the terminal axons of primary afferents within laminae I and II ( substantia gelatinosa ) of the spinal cord and in the spinal nucleus of the trigeminal nerve.

Cessation of dosing with morphine creates the prototypical opioid withdrawal syndrome, which, unlike that of barbiturates, benzodiazepines, alcohol, or sedative-hypnotics, is not fatal by itself in neurologically healthy patients without heart or lung problems.

This regulation of cytokines appear to occur via the p38 MAPKs (mitogen-activated protein kinase)-dependent pathway. Usually, the p38 within the dendritic cell expresses TLR 4 (toll-like receptor 4), which is activated through the ligand LPS ( lipopolysaccharide ). This causes the p38 MAPK to be phosphorylated. This phosphorylation activates the p38 MAPK to begin producing IL-10 and IL-12. When the dendritic cells are chronically exposed to morphine during their differentiation process then treated with LPS, the production of cytokines is different. Once treated with morphine, the p38 MAPK does not produce IL-10, instead favoring production of IL-12. The exact mechanism through which the production of one cytokine is increased in favor over another is not known. Most likely, the morphine causes increased phosphorylation of the p38 MAPK. Transcriptional level interactions between IL-10 and IL-12 may further increase the production of IL-12 once IL-10 is not being produced. This increased production of IL-12 causes increased T-cell immune response.

The following conditions are relative contraindications for morphine:

Tolerance to the analgesic effects of morphine is fairly rapid. There are several hypotheses about how tolerance develops, including opioid receptor phosphorylation (which would change the receptor conformation), functional decoupling of receptors from G-proteins (leading to receptor desensitization), μ-opioid receptor internalization and/or receptor down-regulation (reducing the number of available receptors for morphine to act on), and upregulation of the cAMP pathway (a counterregulatory mechanism to opioid effects) (For a review of these processes, see Koch and Hollt. ) CCK might mediate some counter-regulatory pathways responsible for opioid tolerance. CCK-antagonist drugs, specifically proglumide, have been shown to slow the development of tolerance to morphine.

Morphine can be taken orally, sublingually, bucally, rectally, subcutaneously, intranasally, intravenously, intrathecally or epidurally and inhaled via a nebulizer. On the streets, it is becoming more common to inhale (" Chasing the Dragon "), but, for medical purposes, intravenous (IV) injection is the most common method of administration. Morphine is subject to extensive first-pass metabolism (a large proportion is broken down in the liver), so, if taken orally, only 40–50% of the dose reaches the central nervous system. Resultant plasma levels after subcutaneous (SC), intramuscular (IM), and IV injection are all comparable. After IM or SC injections, morphine plasma levels peak in approximay 20 minutes, and, after oral administration, levels peak in approximay 30 minutes. Morphine is metabolised primarily in the liver and approximay 87% of a dose of morphine is excreted in the urine within 72 hours of administration. Morphine is metabolized primarily into morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) via glucuronidation by phase II metabolism enzyme UDP-glucuronosyl transferase-2B7 (UGT2B7). About 60% of morphine is converted to M3G, and 6–10% is converted to M6G. Not only does the metabolism occur in the liver but it may also take place in the brain and the kidneys. M3G does not undergo opioid receptor binding and has no analgesic effect. M6G binds to μ-receptors and is half as potent an analgesic as morphine in humans. Morphine may also be metabolized into small amounts of normorphine, codeine, and hydromorphone. Metabolism rate is determined by gender, age, diet, genetic makeup, disease state (if any), and use of other medications. The elimination half-life of morphine is approximay 120 minutes, though there may be slight differences between men and women. Morphine can be stored in fat, and, thus, can be detectable even after death. Morphine can cross the blood–brain barrier, but, because of poor lipid solubility, protein binding, rapid conjugation with glucuronic acid and ionization, it does not cross easily. Diacetylmorphine, which is derived from morphine, crosses the blood–brain barrier more easily, making it more potent.

Morphine is primarily used to treat both acute and chronic severe pain. It is also used for pain due to myocardial infarction and for labor pains. There are however concerns that morphine may increase mortality in the setting of non ST elevation myocardial infarction. Morphine has also traditionally been used in the treatment of acute pulmonary edema. A 2006 review however found little evidence to support this practice.

Morphine ( INN ) ( / ˈ m ɔr f iː n / ) (sold under nearly a hundred trade names ) is an opioid analgesic drug, and the main psychoactive chemical in opium. In clinical medicine, morphine is regarded as the gold standard of analgesics used to relieve intense pain. Like other opioids, such as oxycodone, hydromorphone, and diacetylmorphine ( heroin ), morphine acts directly on the central nervous system (CNS) to relieve pain.

Immediate release morphine is beneficial in reducing the symptom of acute shortness of breath due to both cancer and non-cancer causes. In the setting of breathlessness at rest or on minimal exertion from conditions such as advanced cancer or end-stage cardio-respiratory diseases, regular, low-dose sustained release morphine significantly reduces breathlessness safely, with its benefits maintained over time.

Morphine is the most abundant opiate found in opium, the dried latex from unripe seedpods of Papaver somniferum (the opium poppy). Morphine was the first active ingredient purified from a plant source. It is one of at least fifty alkaloids of several different types present in opium, poppy straw concentrate, and other poppy derivatives. The primary source of morphine is chemical extraction from opium.

The minimum lethal dose is 200 mg but in case of hypersensitivity 60 mg can bring sudden death. In serious drug dependency (high tolerance), 2000–3000 mg per day can be tolerated.

In controlled studies comparing the physiological and subjective effects of heroin and morphine in individuals formerly addicted to opiates, subjects showed no preference for one drug over the other. Equipotent, injected doses had comparable action courses, with no difference in subjects' self-rated feelings of euphoria, ambition, nervousness, relaxation, drowsiness, or sleepiness. Short-term addiction studies by the same researchers demonstrated that tolerance developed at a similar rate to both heroin and morphine. When compared to the opioids hydromorphone, fentanyl, oxycodone, and pethidine / meperidine, former addicts showed a strong preference for heroin and morphine, suggesting that heroin and morphine are particularly susceptible to abuse and addiction. Morphine and heroin were also much more likely to produce euphoria and other positive subjective effects when compared to these other opioids. The choice of heroin and morphine over other opioids by former-drug addicts may also be the result of the fact that heroin (also known as morphine diacetate, diamorphine or di-acetyl-morphine ) is an ester of morphine and a morphine prodrug, essentially meaning that they are identical drugs in vivo. Heroin is converted to morphine before binding to the opioid receptors in the brain and spinal cord, where morphine causes the subjective effects, which is what the addicted individuals are seeking.


Morphine