Pharmacology Flashcards
What are the steps in the WHO analgesiac ladder?
- Paracetamol
- NSAIDs
- Weak Opiod (e.g. codeine, tramadol)
- Strong Opiod (e.g. morphine, oxycodone, heroin)
What is the difference between opiates and opioids?
Opiates- substance extracted from opium or of a similar structure to those in opium
Opioids- any agent (including endogenous peptides- endorphines/enkephalins) that act upon opioid receptors
What are some important brainstem regions involved in pain?
The periaqueductal grey (midbrain)
Locus ceruleus (pons)
Nucleus raphe magnus (medulla)
What is the role of the brainstem regions in regulating pain?
- The PAG is excited which produces analgesia. Either through electrical stimulation or by endogenous opioids or morphine.
- Activated PAG project into the NRM. This results in serotonergic and enkephalinergic neurones projecting into the dorsal horn, supressing the nociceptive transmission
- Morphine also excited the NRM neurones
- The LC is also excited. Noradrenergic neurones project into the dorsal horn, inhibiting transmission
How is opioid action mediated?
By G protein-coupled opiod receptors
What are the classifications of opioid receptors? (3)
- µ- responsible for most of the analgesiac action of opioids but also have some major adverse effects
- ð (delta)- contributes to analgesia but activation can be proconvulsant
- k (kappa)- contributes to analgesia at the spinal and peripheral level and activation associated with sedation, dysphoria and hallucinations
What are some side effects of opioids?
- Respiratory- apnoea
- CV- Orthostatic hypotension
- GI- Nausea, vomitting, constipation, increased intrabilliary pressure
- CNS- confusion, euphoria, dysphoria, hallucinations, dizziness, myoclonus, hyperalgesia (with excessive use)
How is morphine metabolised and excreeted?
Metabolised in the liver by glucuronidation
Excreeted by the kidney
How is morphine administered?
IV in high dependency areas or IM, SC, oral in general wards
In chronic pain, oral adminisatration is the most appropriate
Can be given by epidural and intrathecal routes by specialists
For what kind of pain is codeine given?
Its a naturally occuring opioid and is given in those with mild/moderate pain
How is codeine administered?
Orally
Why might codeine be a bad drug of choice in those with constipation?
It has additional anti-diarrhoeal and antitussive activity that may be useful in some cases but adverse causing constipation
What are some semi-synthetic derivitives of codeine with higher potencies?
Oxycodone and Hydrocodone
Through which routes can Fentanyl be given?
IV- to provide analgesia in mantience anesthesia
Also sutibal for transdermal and buccal delivery in chronic pain states (not in acute)
When might Pethidine be used?
In acute pain, particulalrly in labour
