Opioids

The opioid drugs include morphine and its synthetic derivatives. They are powerful analgesics, and have dose-dependent sedative properties.

Opioids have additional recognised effects. They:

• Decrease the sensitivity of the respiratory centres of the brain to carbon dioxide.
• Give potent cough suppression.
• Cause emesis.
• Constrict the pupils (miosis).
• Reduce gastro-intestinal motility.
• Lead to histamine release.

Opioid Antagonists

Naloxone is an antagonist to endogenous opioids. It is frequently used in human medicine to antagonise opioid narcotics in the incidence of overdose. Naloxone may be administered intravenously, intramuscularly, intrathecally or subcutaneously. It has a short duration of action (1-2 hours) and so repeated administrations may be necessary.