Pharmacology

Question 1

Opiod receptors

Answer 1

MOR, DOR ad KOR type
they are found in the CNS, PAG, dorsal horn and peripheral tissues including GIT
Receptors are coupled with G protein, they inhibit the nerve by reducing intracellular cAMP or K+ efflux (hyperpolarisation) leading to reduction in neuronal excitability

Question 2

Peripheral mechanism of opiods

Answer 2

hyperpolarisation of nerve, makes it less easily excitable and reduces pain transmission

Question 3

Central mechanism of opioids

Answer 3

inhibit substance P release from 1st order neuron in dorsal horn, hyperpolarisation of 2nd order neurond

Question 4

Supraspinal mechanism of opiods

Answer 4

euphoria- alters pain perception

and activation of descending pathways

Question 5

Adverse reaction of opioids

Answer 5

drowsiness, repsiratory depression, bradycrdia, nausea, constipation,

Question 6

Opiod receptor antagonists

Answer 6

Bind to receptors causing receptor to become non-functional and preventing agonists from interacting with same receptor
e.g. Naloxone- strong affinity for opioid receptors, it reverses opioid overdoses, used in cases of respiratory arrest in heroin overdoses.
Can buy agonist- antagonist preparations to offset side effects

Question 7

NSAID mechanism of action and types

Answer 7

Normally, arachodonic acid becomes prostaglandins vis cyclo-oxygensae enzymes. NSAID blocks these enzymes
COX1-prostaglandins for homeostasis
COX2- prostaglandins for inflammation

Question 8

Side effects of NSAIDs

Answer 8

GIT upset, rash, renal failure, hypertension

Question 9

Paracetomal mechanism of action

Answer 9

inhibits prostaglandin synthesis centrally and modulates pain via serotongeric and cannabinoid receptors

Question 10

Paracetamol side effects

Answer 10

less side effects than NSAIDs, taken in excess can lead to hepatoxicity

Question 11

Pregabalin mechanism of action

Answer 11

reduce synpatic release of subsance P, glutamate and noreadrenalin. aka lyrica

Question 12

Gabapentin mechanism of action

Answer 12

may activate GABA neurons or inhibit NMDA receptors

Question 13

Carbbamezaepine mechanism of action

Answer 13

tegretol- firsst line therapy for trigeminal neuralgia. Promotes sodium efflux and delays rate of recovery of voltage gated sodium channels from inactivated state.

Question 14

Tricyclic antidepressants mechanisms

Answer 14

e.g. amitryptiline. Blocks the pump on the presynaptic terminal responsible for serotonin and NA reuptake
Increased levels of these neurotransmitters = descending pain modulation

Question 15

Corticosteroids

Answer 15

Steroid based= can enter cell
Bind to corticosteroid receptors in the nucleus and interact with DNA to alter gene expression
-Produce anti-inflammatory proteins (e.g. lipocortin, inhibits phospholipidase)
-Decreased production of inflammatory mediators and enzymes (e.g. less COX gene expression

Question 16

Muscle relaxants

Answer 16

Stimulates GABA receptors in the spinal cord and also blocks release of substance P.

Question 17

Local anaesthetic

Answer 17

Bind to receptors om membrane-bound channels and block influx of sodium= blocked transmission of pain signals to second order neuron

Question 18

Anti-depressant side effects

Answer 18

nausea, impaired sexual function, dry mouth, fatigue, insomnia, drowsiness, blurred vision

Question 19

Neuropathic pain recommendation

Answer 19

Offer a choice of amitriptyline, duloxetine, gabapentin or pregabalin as initial treatment for neuropathic pain
• Consider tramadol only if acute rescue therapy is needed.
• Consider capsaicin cream for people with localised neuropathic pain who wish to avoid, or who cannot tolerate, oral treatments.

Question 20

Managment of acute LBP

Answer 20

1. reassurance, exercise, education, non-pharmalogical
2. NSAIDs with adjunct
3. NSAIDs with weak opiods (e.g. codeine, tramadol, oxycodone) with adjunct
4. NSAIDs + strong opiods (fentanyl, morphine)
5. Local corticosteroid injection if very cute

Question 21

Tramadol mechanism of action

Answer 21

Opiod receptor agonist + SSRI/ SNRI

Question 22

Chronic LBP management

Answer 22

CBT, exercise, reassurane, NO OPIOIDS (opiod induced analgesia and tolerance) NO paraceetomal, NSAIDs short term, antidepressants

Question 23

CRPS

Answer 23

hyperalgesia, allodynia, chnages in skin colour, blood supply, temperature, sweating, motor changes, changess in urine or other systems, affects widespread areas,

Question 24

Diazepam

Answer 24

binds to benzodiazpam receptor > enhances GABA and chloride influx (hyperpolarisation)

Question 25

Capsacin

Answer 25

activates TRPV1 receptors and depletes the neurons of SP therefore inhibiting pain