OPIOIDS

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Medical University of Sofia, Faculty of
Medicine Department of Pharmacology and Toxicology

• OPIOIDS
• NIRALI PATEL
• (2009)

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OPIOIDS

• DEFINITION
• Any natural or synthetic compound that imitates
  properties of natural narcotics
• Is an analgesic that works by binding to opioid
  receptors, which are found principally in the
  central nervous system and the gastrointestinal
  tract. The receptors mediate both the beneficial
  effects, and the undesirable side effects.

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• CLASSIFICATION
• Natural opiates
• Alkaloids contained in the resin of the opium
  poppy (morphine, codeine, thebaine)?
• Semi-synthetic opiates
• Created from the natural opioids (hydromorphone,
  hydrocodone, oxycodone,oxymorphone, desomorphine,
  diacetylmorphine (Heroin)?
• Fully synthetic opioids
• Created from chemical compounds (fentanyl,
  pethidine, methadone, tramadol and propoxyphene)?
• Endogenous opioid peptides
• Produced naturally in the body (endorphins,
  enkephalins, dynorphins, and endomorphins)?

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• PHARMACOKINETICS
• Distribution - Widely distributed throughout body
  tissue concentration in kidney, liver and spleen
  is higher than that in plasma. Only a small
  fraction enters brain rather slowly. Morphine
  crosses placenta.
• Metabolism - Extensively in the liver.
  Metabolic-breakdown is the primary method of
  opioid duration
• Excretion - Metabolites are excreted by the
  kidneys. A small fraction is excreted in stool
  through the biliary tract.
• Routes of administration - Oral, Transmucosal,
  I.V (most rapid acting), I.M and S.C

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• PHARMACODYNAMICS
• They reduce pain by binding to receptor sites
  (mainly mu-receptors) in the central and
  peripheral nervous system. After stimulation of
  receptors they mimic the effects of naturally
  occurring opiates that are apart of the body's
  own pain relief system.
• Processing of pain information is inhibited by a
  direct spinal effect at the dorsal horn, which
  involves presynaptic inhibition of the release of
  tachykinins like substance P.
• Emotional response to pain altered by opioid
  actions on the limbic cortex
• Act presynaptically to block Ca2 uptake and
  consequently inhibit neurotransmitter release.
  Opioids have been shown to inhibit the release of
  many neurotransmitters, including substance P,
  acetylcholine, norepinephrine, glutamate, and
  serotonin.

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• PHARMACOTHERAPUTICS
• Opioids are prescribed to relieve severe pain in
  acute, chronic and terminal illnesses. They are
  also used to reduce anxiety, control diarrhea and
  suppress coughing.
• ADVERSE EFFECTS
• ACUTE
• Miosis, Respiratory Depression, Nausea and
  vomiting, Sedation, Skeletal muscle hypertonus,
  Euphoria, Constipation, Vasodilatation, Urinary
  retention, Bradycardia, Biliary Spasm, Morphine
  poisoning.
• CHRONIC
• Tolerance, Physical Dependence and Apnea (in
  newborns)

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• DRUG INTERACTIONS
• Drugs that may effect opioid analgesic activity
  include amitriptyline, diazepam, phenytoin,
  protease inhibitors and rifampin.
• Drugs that may be affected by opioid analgesics
  include carbamazepine, warfarin, beta-adrenergic
  blockers and calcium channel blockers.
• Use of opioid agonists with other drugs that
  decrease respiration, such as alcohol, sedatives,
  hypnotic and anesthetics, increase the risk of
  severe respiratory depression.
• Taking tricyclic antidepressants, phenothiazines,
  or anticholinergics with opioid agonists may
  cause sever constipation and urine retention.