Analgesics Flashcards
What is acute nociceptive pain?
Short term pain with an easily identifiable cause
What is chronic neuropathic pain?
Persisting pain that has outlived its purpose as it no longer helps the body prevent further injury.
What is allodynia?
Pain from a stimulus that does not normally cause pain.
What is parenthesis?
Painful feelings with no obviously stimulus (pins and needles)
Where is inflammation experienced in the pain pathway?
In the spinal cord.
What is the role of opioids?
Agonists.
Modify transmission of pain signals.
Opioids decrease neurotransmitter release in the brain stem and activate inhibitory pathways.
What are the roles of antidepressants and anti epileptics?
Trigeminal neuralgia
Used to treat neuropathic pain (pain that opioids can’t treat).
What are the disadvantages of opioids?
Side effects- dose related nausea, vomiting, constipation, drowsiness, hypotension, respiratory depression, sedation and dependence.
Interactions- Mixing with alcohol increases hypotension and sedation.
MAOIs increases CNS excitation/inhibition.
Carbamazepine- decreases plasma concentration of methadone.
What is the neuropharmacology of opioids?
Mimic endogenous ligands “enkephalin”- the bodys natural analgesia.
Act as agonists at opioid receptors u,k,a
Where do a opioids target?
CNS and peripheral sensory neurones. Can contribute to analgesia.
Where do u opioids target?
Most analgesic opioids are u-recceport agonists.
Target CNS, spinal cord, peripheral sensory neurons, GI tract.
Responsible for most side effects
What do k opioids target?
Spinal cord and peripheral sensory neurones.
Casues sedation and dysphoria but few side effects.
Does not contribute to dependency.
What are the actions of antidepressants?
Serotonin and noradrenaline for part of the body’s natural analgesia. Serotonin and noradrenaline mediate descending inhibition of pain pathways in the brain and spinal cord.
Antidepressants inhibit the reputake of these substances, making their effects last longer.
What are SNRIs?
Serotonin and Noradrenaline Reuptake Inhibitors (SNRIs)
Highly effective for neuropathic pain
What are examples of SNRIs?
Venafaxine and Duloxetine
What are SSRIs
Selective Serotonin Reuptake Inhibitors.
Not particularly effective analgesics.
Work well in the disease environment- e.g with patients with HIV
What are examples of SSRIs?
Paroxetine and Citalopram
What are the disadvantages of SNRIs?
Side effects- nausea, somonolence, insomnia and dizziness, headache.
Cautions- not to be used with epilepsy, glaucoma, cardiac disease, pregnancy.
Interaction- Alcohol-Increased sedation. NSAIDS/aspirin- increased risk of bleeding.
Tramadol- Increased CNS toxicity.
What are the actions of anti-epileptic agents?
Inhibit voltage gates sodium and calcium channels.
Inhibit glutamate, GABA and glycine receptors.
Inhibit action potential firing and prevent impulse transmission.
What are examples of anti-epileptic drugs?
Carbamazine and Gabapentin.
Gabapentin is the drug of choice, however is not to be used during pregnancy.
What are the side effects of anti epileptic drugs?
Dizziness, diplopa, drowsiness, hepetoxicity, renal impairment, dyspepsia and tremour.
What are the mechanisms of actions for local anaesthetics?
Prevent nerve-nerve cell communication- inhibit sodium channels on NMDA receptors.
Lidocane- a sodium channel blocker
Ketamine- blocker of glutamte receptors.
What are the side effects of local anaesthetics?
Lidocane- Confusion, respiratory depression, convulutions, hypotension, bradycardia.
Ketamine- hypertension, tachycarida, tremor, diplopia and myocardial depression.
