Opioids Flashcards
What are opiates?
Drugs derived from poppy opium
What are opioids?
Drugs that work in a similar way to opiates but are not directly derived from poppy opium
What are the three classes of opioids?
Natural, semi-synthetic and synthetic
Comment on the acute efficacy of opioids
Highly efficacious and with few side-effects
Which opioid characteristic is linked to dependency?
The higher efficacy, the more likely to cause dependency
Do opioid receptors show stereoselectivity?
Yes. Levorphanol and dextromethorphan are examples
Where in the body are most opioid receptors found?
In the CNS
Are opioid receptors metabotropic or ionotropic?
GPCR metabotropic
What is the mu-type receptor positively and negatively coupled to?
An opioid receptor that when activated results in K+ channels being opened.
What differentiates mu, kappa and delta opioid receptors?
They have different pharmacology and are expressed differently in different neuronal regions
What is a non-selective opioid antagonist?
Naloxone
Name is a pure opioid agonist?
Levorphanol
What form do endogenous opioid ligands take?
Peptides
Name the three primary endogenous opioid ligands
1) Met and Leu enkephalins
2) Dynorphin
3) Endorphin
Morphine most similarly resembles which endogenous ligand?
Met enkephalin
What do endogenous ligands act to do?
Reduce neurotransmission on the presynaptic membrane in central pathways
Where do endogenous opioid ligands act to produce analgesic effects?
Neurotransmission at the dorsal horn
What are some other effects of opioids?
Anti-tussive properties, hyposensitivity of primary CO2 respiratory centre, Induce histamine release, depressed spinal reflex, miosis, reduced gastric motility
Side effects are driven predominantly by which receptor?`
Mu-type opioid receptor
What is opioid tolerance?
The more frequently opioids are taken, the greater the dose required to produce the same effect due to physiological desensitisation
How does overdose occur with regard to tolerance?
When the dose required to produce a response is greater than the lethal dose
What is dispositional tolerance
Pharmacokinetic tolerance refers to a reduction of drug reaching the target
What is direct tolerance?
Direct pharmacodynamic tolerance refers to a reduction in target receptors or a reduction in the efficacity of target receptors
What is indirect tolerance?
Indirect pharmacodynamic tolerance refers to a reduction in downstream targets and how efficacious the intracellular messengers are
What is the difference between drug-induced dependence and addiction?
Dependence is the physiological dependence whereby withdrawal may result in serious physical effects on the body. Addiction, however, is a behavioural dependence
Which neural pathway must be present for the reward effects to take place?
The mesolimbic pathway MUST be present.
