Weak Opiods Flashcards
Give some examples of weak opioids
Codeine, Dihydrocodeine, Tramadol
How do weak opioids work?
Codeine and dihydrocodeien are metabolised in the liver to small amounts of morphine and dihydromorphine.
Why are some people immune to the effects of codeine?
10% of the Caucasian population do not have the enzyme CYP450 2D6 which is required for the metabolism of codeine so do not find it has an analgesic effect
What is tramadol?
Tramadol is a sunthesic analogue of codeine.
Tramadol and its metabolite are also mu receptor agonists.
Why is tramadol different to other weak opioids?
Unlike other opioids, tramadol also affects serotonergic and adrenergic pathways, where it is thought to act as a serotonin and noradrenaline reuptake inhibitor. This probably contributes to its analgesic effect.
What are the common uses of codeine?
- Mild to moderate pain relief when paracetamol and other analgesics are not enough. (Second on pain ladder)
- After operations
What are the contraindications of using weak opioids?
Tramadol lowers the seizure threshold so should not be used in uncontrolled epilepsy
When should weak opioids be used with caution?
Respiratory disease
Elderly
Hepatic and renal insufficiency
What are the common interaction with codeine and tramadol?
- Other sedative drugs (antipsychotics, TCAs and benzodiazapines)
- Alcohol
- Tramadol should not be used with pother drugs that lower the seizure threshold e.g. SSRIs and TCAs
- Cimetidine inhibits opioid metabolism
What are the common side effects fo weak opioids?
- Nausea - prescribe with anitimetic
- Constipation - prescribe with laxative
- Dizziness and drowsiness
- *CODEINE MUST NEVER BE GIVEN IV
Why should codeine never be given IV?
Causes an anaphylactic like reaction (mediated by histamine but not allergic)
Why might you see a patient after an operation with a red mark on their thigh?
Anaesthetists may sometimes give an IM injection of codeine towards the end of an operation, while the patient is still under general anaesthesia, to provide post- operative analgesia. This may cause a red patch to form at the injection site (which, for reasons of accessibility, is usually the lateral aspect of the thigh).
