Pharmacology of Opioids

Pharmacology of Opioids

This Daily Doodle represent the lecture on the pharmacology for acute pain with a focus on opioids. The lecture started off with a definition of pain, “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” (International Association for the Study of Pain). Pain is always subjective and everyone defines and expresses pain differently.

A few other definitions that we went over include:
– Narcotics = the original definition described any psychoactive drug that produce sleep
– Opiates = drugs that are derived from opium (from the opium poppy plant)
– Opioids = drugs that bind to opioid receptors

Sites of Action of Opioids include the Brain, Brainstem, Spinal cord, Primary afferent neurons, Medullary respiratory centre, Medullary chemoreceptor zone and the GI tract (hence all the GI side effects)

Central effects of opioids include:
• Analgesia
• Hyperalgesia (at high doses)
• Cough suppression
• Euphoria (also dysphoria)
• Sedation
• Respiratory depression (↓respiratory rate)
• Nausea & vomiting
• Pruritus (itching)
• Miosis (pupillary constriction)
• Truncal rigidity

Some of the peripheral effects of opioids include:
• Constipation
• Urinary retention
• Constriction of sphincter of Oddi (biliary colic)
• Bradycardia (no other significant direct effects on the heart)
• Hypotension (due to vasodilation)

Reference
1.  UBC Opioid Pharmacology Lecture, January 17, 2012

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