Strong opioid analgesic

Morphine and its derivatives make up the step 3 class of analgesics. This class of drugs is intended to treat intense pain which does not respond to the first two steps defined by the WHO. Morphine and its derivatives are very similar to step two drugs in both action mechanism and in possible side effects.

How do the strong opioid analgesics work ?

Opioid receptors control several functions in the brain including response to pain. Step 3 analgesics or strong opioids act directly on these receptors to relieve severe pain.

Do they have contraindications or precautions?

The side effects of these medicines are the same as those of the step 2 analgesics: constipation, drowsiness, nausea and vomiting. They can also cause dependency and for this reason their prescription is regulated.

Sources:

• Merck Manual – 4th edition;
• Principles of internal medicine, TR Harrison, ed. Flammarion.