opoid pharmacology Flashcards
what are the simple chemical modifications?
Diamorphine Oxycodone Dihydrocodeine
what are natural occurring opioids from the opium poppy?
morphine
codeine
what are the routes of administration?
Pharmacokinetics
Oral
Bioavailability
first pass metabolism by the liver
describe first pass metabolism
First pass metabolism by the liver – 50% of oral morphine is metabolized by the first pass metabolism. Halve the dose if given IM/ IV etc.
how long does a single dose of morphine last for?
3-4 hours
A. Sub-cutaneous
B. IM
C. IV
Which will be the fastest?
IV then IM
what does opium contain?
morphine and codeine
what is the current legislation for controlled drug use ( CDs) ?
Misuse of drugs act 1971
what class are opioid drugs?
class A
what are the practical issues with CDs?
Secure storage
CD books - two signatures needed
how do opioids work?
they use the existing pain pathway
natural endorphins ( endogenous and morphine) and enkephalins
Descending inhibition of pain
Part of the fight or flight response
Never designed for sustained activation
what acts via second messengers in the path pathway?
G protein coupled receptors- amplifies the effect
what do opioids do?
Inhibit the release of pain transmitters at spinal cord and midbrain - and modulate pain perception in higher centres - euphoria - changes the emotional perception of pain
what does sustained activation lead to with opioids?
tolerance and addiction
what do kappa agonists do?
cause depression instead of euphoria
what agonists are currently used?
μ agonists
define potency
whether a drug is ‘strong’ or ‘weak’ relates to how well the drug binds to the receptor, the binding affinity.
define efficacy
the concept of full or partial agonists
- does it work
define tolerance
down regulation of the receptors with prolonged use. Need higher doses to achieve the same effect
define dependence
psychological – craving, euphoria
define opioid withdrawal
starts within 24 hours, lasts about 72 hours
side effects of opioid use
Respiratory depression
Sedation
Nausea and vomiting
Constipation
Itching
Immune suppression
Endocrine effects
how are opioids delivered?
sometimes are delivered epidurals but mostly given systemically
where are opioid receptors located?
do exist outside of the pain system
e.g. digestive tract, respiratory control centre
