Analgesics

Question 1

Define acute/nociceptive pain

Answer 1

short term pain, easily identifiable cause, responds well to medication

Question 2

Define chronic/neuropathic pain

Answer 2

pain which persists, no longer helps the body to prevent any further injury

Question 3

Define allodynia

Answer 3

pain from stimulus that does not normally cause pain

Question 4

Define parasthesis

Answer 4

painful feelings with no apparent stimulus

Question 5

Pain management

Answer 5

Assessments:

• type of pain (nociceptive/neuropathic)
• form of pain (acute/chronic)
• severity of pain (pain scores)
• routes of admission (iv/oral)

Question 6

Opioids

Answer 6

modify transmission of pain signal and the subjective perception of pain
act at the level of the spinal chord and CNS to:
- decrease neurotransmitter release and block post-synaptic receptors
- activate inhibitory pathways
mimic our endogenous pain killers ‘enkephalins’
3 types of receptors
act as suppressors

Question 7

Opioid advantages and disadvantages

Answer 7

Advantages:
- highly effective, variety of routes, range of duration of effects
Disadvantages:
- SE (dose related)
> nausea, vomiting, constipation
> drowsiness, respiratory depression, sedation, dependency
- cautions/contraindications:
> acute respiratory depression, acute alcoholism, head injury
- interactions:
> alcohol increases hypotensive and sedative effects
> MAOIs increase CNS excitation
- Carbamazepine decreases plasma concentration of the membrane

Question 8

Opioid receptors

Answer 8

Mu = found in CNS, spinal chord, peripheral sensory neurones, GI tract
responsible for most analgesic effects
responsible for SE
Kappa = found in CNS, spinal chord, peripheral sensory neurons
sedation and dysphoria, few SE, no dependance
Delta = found in CNS, peripheral sensory neurons, may contribute to analgesia

Question 9

Morphine

- opioid

Answer 9

oral, i.v, s.c
treats acute and chronic pain
SE = respiratory depression, sedation, constipation, nausea, vomiting, itching, dependence

Question 10

Diamorphine

-opioid

Answer 10

oral, i.v
acute and chronic pain
more rapid than morphine, metabolised to morphine
SE = respiratory depression, sedation, constipation, nausea, vomiting, itching, dependence

Question 11

Hydromorphone

-opioid

Answer 11

oral, i.v
acute and chronic]
less sedative, SE same as morphine

Question 12

Methadone

- opioid

Answer 12

oral
chronic pain
less euphoric, SE same as morphine

Question 13

Pethidine

- opioid

Answer 13

oral, i.v, i.m
acute and intense pain
SE = anticholinergic effects, risk of excitement and convulsion, same as morphine

Question 14

Anti-depressants and analgesia

Answer 14

SNRI = Serotonin and Noradrenaline Re-uptake inhibitors
- highly effective for neuropathic pain but not in all patients
- actions independent of anti-depressive effects
Eg. Venlafaxine, Duloxetine
SSRI = Selective Serotonin Re-uptake inhibitors
- not particularly effective GA
- appear to work well in disease environments eg diabetes
Eg. Paroxetine, Citalopram

Question 15

Duloxetine

- anti-depressant

Answer 15

prescribed for peripheral neuropathy, particularly diabetic neuropathy
SE = nausea, insomnia, dizziness
cautions/contraindications:
epilepsy, diabetes, cardiac disease, pregnancy/breast feeding
interactions:
alcohol increases sedation
NSAIDS/aspirin increase risk of bleeds
Tramadol increase risk of CNS toxicity

Question 16

Venlafaxine

- anti-depressant

Answer 16

prescribed for diabetic neuropathy
SE = nausea, sedation, headache and dizziness 
cautions/contraindications:
epilepsy, diabetes, cardiac disease, pregnancy/breast feeding
interactions:
alcohol increases sedation
NSAIDS/aspirin increase risk of bleeds
Tramadol increase risk of CNS toxicity

Question 17

Anti-epileptics and analgesia

Answer 17

inhibit voltage gated sodium channels 
inhibit voltage gated calcium channels 
inhibit GABA and glycerine receptors
> inhibit action potential firing
> prevent impulse transmission
> limit neuronal excitation
> enhance neuronal inhibition

Question 18

Carbamazepine

Answer 18

used to treat glossopharyngeal neuralgia, post hepatic neuralgia, diabetic neuropathies
SE: dizziness, fatigue, nausea, hepatotoxicity, renal impairments
cautions/contraindications:hepatic/ renal impairment, cardiac disease, pregnancy, history of bone marrow disease

Question 19

Gabapentin

Answer 19

used to treat various neuropathic pain states:
complex reginal syndrome, deafferentation neuropathy of the face,sciatic pain
drug of choice due to limited side effects
SE = anorexia, tremor
cautions: renal impairment, pregnancy

Question 20

Local anaesthetics

Answer 20

inhibit voltage gated sodium channels to prevent nerve-nerve cell communication
- inhibit firing
- prevent impulse transmission
Eg. Lidocaine, Ketamine

Question 21

Lidocaine

Answer 21

sodium channel blocker
effective in non-cancer patients
i.v
SE = CNS effects (confusion), respiratory depression, hypotension, bradycardia
cautions/contraindications= epilepsy, hepatic/respiratory impairment, atrial fibrillation, heart failure

Question 22

Ketamine

Answer 22

blocker of glutamate receptors
injectable, not favourable due to side effects
SE = hypertension, tachycardia, tremor, myocardial depression
cautions/contraindications = angina, hypertension, heart failure, aneurysm, psychotic disorders

Question 23

What are the 4 anti-depressants effective as analgesics?

Answer 23

Venlafaxine, Duloxetine = SNRI

Citalopram, Paroxetine = SSRI