Morphine

This article is about the opiate. See Morphine (band) for information about the alternative rock group.

Morphine (INN) (IPA: ) is a powerful opioid analgesic drug and is the principal active agent in opium. Like other opiates, morphine acts directly on the central nervous system (CNS) to relieve pain, and at synapses of the arcuate nucleus, in particular. Side effects include impairment of mental performance, euphoria, drowsiness, lethargy, and blurred vision. It also decreases hunger, inhibits the cough reflex, and produces constipation. Morphine is highly addictive when compared to other substances, and tolerance and physical and psychological dependence develop quickly. Patients on morphine often report insomnia and nightmares.

The word "morphine" is derived from Morpheus, the god of dreams in Greek mythology.

Medical use

Administration

Morphine may be given parenterally as subcutaneous, intravenous, or epidural injections. When injected, particularly intravenously, morphine produces an intense contraction sensation in the muscles and thus produces a powerful 'rush'. The military sometimes issues morphine loaded in an autoinjector.

Orally, it comes as an elixir, concentrated solution, powder (for compounding) or in tablet form. Morphine is rarely supplied in suppository form. Due to its poor oral bioavailability, oral morphine is only one-sixth to one-third of the potency of parenteral morphine. Morphine is available in extended-release capsules for chronic administration, as well as immediate-release formulations.

Uses

Morphine is used legally:

analgesic in hospital settings for
- Pain after surgery
- Pain associated with trauma
In the relief of severe chronic pain
- Cancer pain
- Pain from kidney stones
As an adjunct to general anesthesia
In epidural anesthesia
For palliative care (i.e. to alleviate pain without curing the underlying reason for it)
As an antitussive for severe cough
As an antidiarrheal in chronic conditions (e.g., for diarrhea associated with AIDS)
To relieve breathlessness in patients in respiratory failure

Contraindications

Acute pancreatitis (this may be a result of morphine use as well)
Renal failure (due to accumulation of the metabolite morphine-6-glucuronide)

Pharmacology

Morphine is an opioid receptor agonist – its main effect is binding to and activating the µ-opioid receptors in the central nervous system. Activation of these receptors is associated with analgesia, sedation, euphoria, physical dependence and respiratory depression. Morphine is also a κ-opioid receptor agonist, with this action associated with spinal analgesia and miosis.

Legal classification

In the United Kingdom, morphine is listed as a Class A drug under the Misuse of Drugs Act 1971.

In the United States, morphine is classified as a Schedule II drug under the Controlled Substances Act.

In Australia, morphine is classified as a Schedule 8 drug under the Therapeutic Goods Act 1989 (2003).^*

Internationally, morphine is a Schedule I drug under the Single Convention on Narcotic Drugs ^*.

History and Abuse

Morphine was first isolated in 1804 by the German pharmacist Friedrich Wilhelm Adam Sertürner, who named it "morphium" after Morpheus, the Greek god of dreams. But it was not until the development of the hypodermic needle (1853) that its use spread. It was used for pain relief, and as a "cure" for opium and alcohol addiction. Its extensive use during the American Civil War resulted in over 400,000 sufferers from the "soldier's disease" (addiction), though some believe this to be erroneous ^*.

Heroin (diacetylmorphine) was derived from morphine in 1874. As with other drugs, its possession without a prescription was criminalized in the US by the Harrison Narcotics Tax Act of 1914.

Morphine is routinely carried by soldiers on operations in an autoinjector.

Morphine was the most commonly abused narcotic analgesic in the world up until heroin was synthesized and came into use. Even today, morphine is the most sought after prescription narcotic by heroin addicts when heroin is scarce.

In a randomised double-blind study with crossover at an outpatient clinic in Bern, Switzerland, morphine was proven to have stronger side-effects than heroin at equianalgesic doses. Respiratory depression, miosis, sedation, itchiness, and euphoria were more pronounced with morphine.

External links

Morphine Apparently in Your Head -- Wired Magazine article about endogenous production of morphine
Morphine, Molecule of the Month.

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