Strong Opiods Flashcards
Name a common strong opioid
Morphine
How does morphine work?
Activates the opiod (mu) receptor in the CNS
Activation of the mu receptor causes:
- Decreased neuronal activity and pain transmission
- Decrease response to hypercapnoea and hypoxia in the medulla
- Reduced sympathetic fight or flight response
- Depression of cough centre
- Increased smooth muscle tone in large bowel and reduced bowel motility
What are the common uses of morphine?
- Acute severe pain: MI/ Post operative
- Chronic pain: on analgesic ladder when paracetamol, NSAIDs and mild opioids dont work
- Relief of breathlessness in palliative care
- Relief of breathlessness in acute pulmonary oedema: along with oxygen, furosemide and nitrates
When should morphine be used with caution?
- Renal/Hepatic insufficiency (elimination this way)
- Elderly
- Respiratory failure - unless paliative
What are the contraindications of using morphine?
Avoid in biliary colic: may cause construction of sphincter of oddi and worsen symptoms
What are the common interactions with morphine?
- Other sedative drugs e.g. TCAs, antipsychotics and benzodiazepines
- Alcohol: enhances sedative effects
- Cimetidine: inhibits opioid metabolism
What are the common side effects of using morphine?
- Euphoria
- Dissociation
- Respiratory depression
- Tolerance
- Addiction
- Constipation (increase SM tone in large bowel and reduced motility)
- Nausea and vom (stimulation of chemoreceptor trigger zone)
- Pin prick pupils (edinger westfelt nucleus)
- Sweating, vasodilation, itching and uticuria of skin due to histamine release
- Withdrawal reaction (opposite to clinical effects - anxiety, breathlessness and pain)
When do you give morphine IV and when do you give it orally?
IV: acute pain
Oral: chronic pain
How is morphine excreted?
Hepatic metabolism
Biliary and urine excretion
