Pharmacology Analgesic Agents

Question 1

What is pain?

Answer 1

Unpleasant sensory and emotional experience - primarily associated w/ tissue damage

Question 2

Pain modulation?

Answer 2

Amount of pain not always relate severity of tissue damage

Anxiety, cultural and contextual factors can increase pain

Question 3

What are some tx of dental pain?

Answer 3

NSAIDS, nerve block, option, physiological factors

Question 4

What is a placebo?

Answer 4

Pharmacologically and physiologically inter

- Not ineffective can have measurable effect

Question 5

What is step 1 on pain ladder - what does it tx and what is used?

Answer 5

Used for mild pain

Use paracetamol/NSAIDS - non opioid

Question 6

Explain mechanism of paracetamol and dosing

Answer 6

Inhibit synthesis of prostaglandins
Analgesics, antipyretic, not anti-infam
Ig every 4-6 hours - max dose 4g 24 hrs

Question 7

Explain mechanism of NSAID

Answer 7

Irreversible inhibition of cyclo-oxygenase

Inhibitor of prostaglandins and thromboxane

Question 8

Explain side effects of NSAIDs

Answer 8

GI - cause GI bleed and ulceration
Renal - decrease intra-renal blood flow
Platelet - COX inhib = bleeding tendency
Resp - aspirin sensitivity in asthmatic

Question 9

What is step 2 on pain ladder - what does it tx and what is used?

Answer 9

Used for moderate pain

Use weak option +/- non-opioid

Question 10

What opiod would you use for moderate pain?

Answer 10

Codeine/ di-hydrocodiene

–> both metabolised into morphine (variable depending on person dependent enzyme)

Question 11

Effect of weak opioid (codeine)

Answer 11

CV: reduced sympathetic outflow and increased vagal tone (bradycardia, hypotension)
Resp: resp depression - inhibit cough relex
GI: decreased motility - constipation and nausea

Question 12

What effect do opioid have on CNS - what negative effect can this have?

Answer 12

Sedation and euphoria
Spinal cord: reduce pain fibre transmission at kappa opioid receptor
Brainstem: reduce pain projection at mu opioid receptor
- cause reduced brainstorm response - hypoxia

Question 13

How to reverse opioids?

Answer 13

Naloxone 400mg I.V - reversal Mu receptors

Question 14

Problem w/ opioid dependency and how occurs?

Answer 14

Chronic opioid use - decrease effect as CNS becomes more tolerant

Withdrawal - hypertension, tachycardia, anxiety, diarrhoea

Question 15

What is tramadol?

Answer 15

Newer oral opioid - as effective as codeine with less variability

Question 16

What is example of weak opioid + non-opioid

Answer 16

Co-codamol

Question 17

What is step 3 on pain ladder and what would you use to tx?

Answer 17

Step 3 is management of severe pain

Tx w/ strong opioid +/- non-opioid

Question 18

Give example of strong opioid

Answer 18

Morphine, diamorphine, fentanyl patch

Question 19

How would you give post-op analgesia?

Answer 19

IV in recovery - 2mg increment every 3 min until comfortable - 10-20mg
Ward care - 10mg morphine SC 3 hourly w/ antiemetic

Question 20

What is step 4 on pain ladder and how would you tx?

Answer 20

Step 4 is management of severe chronic pain
Tx = oral morphine, S.C infusion of morphine or diamorphine and fentanyl patch

Other: antidepressant, physiological support and pain management

Question 21

Use of gabapentin and pregabalin?

Answer 21

Effective neurogenic pain - decrease central transmission and pain projection

Question 22

Use of antidepressants in chronic pain?

Answer 22

Useful for neurogenic pain