Pain

Question 1

Name 6 drug interactions with NSAIDs

Answer 1

• Warfarin: increased anticoagulation- bleeding
• methotrexate toxicity: displacement from albumin and reduced renal clearance
• digoxin toxicity: reduced renal clearance
• lithium: reduced renal clearance - tremors and seizures
• ace-i: inhibit pg mediated vasodilation - treatment fail ht
• diuretics: salt and water retention -treatment fail ht

Question 2

What is underlying cause scolene apnea?

Answer 2

Some patients (especially Caucasians) unable to hydrolyse scolene with pseudo/burtyryl- cholinesterase leading to prolonged muscle paralysis

Question 3

Codeine is metabolised to morphine by which CyP 450 isoenzyme?

Answer 3

Cyp2d6

Question 4

Define allodynia

Answer 4

Non-painful stimuli perceived as painful

Question 5

Name the 2 primary sensory fibres that carry afferent signals for pain.

Answer 5

• A delta fibres: thinly myelinated, acute productive pain, rapid activation
• C fibres: unmyelinated thus slow, diffuse dull chronic pain

Question 6

Name and describe 3 types nociceptors

Answer 6

• Mechanosensitive nociceptors of A delta fibres: intense mechanical stimulation eg pinching with pliers or injury to tissues
• thermosensitive nociceptors of A delta fibres: temperature
• polymodal nociceptors of c fibres: noxious stimuli which are mechanical, thermal or chemical.

Question 7

Name 5 chemical mediators of the pain response.

Answer 7

• Potassium, released by damaged cells
• histamine, by mast cells
• prostaglandins, damaged cells
• serotonin, platelets activated by injury
• bradykinin, blood plasma

Question 8

Name 4 functions prostaglandins.

Answer 8

• Activate inflammatory response, pain and fever
• blood clots formation (thromboxane a2) when BV damaged
• induce labour and other reproductive processes
• other organs: giT inhibit acid synth and increase secretion protective mucous; increase blood flow kidneys; leukotrienes promote bronchoconstriction associated with asthma

Question 9

How is bradykinin produced?

Answer 9

By action of kallikrein, trypsin or plasmin on high-molecular-weight kininogen, a plasma a2 globulin.

Question 10

Which 5-ht receptors are present on c fibres?

Answer 10

5ht3 and 5ht2a

Question 11

What causes mast cells to release histamine?

Answer 11

Nociceptor’s release “substance p” which causes mast cells to release histamine and in turn stimulate nociceptors

Question 12

Name 3 neurotransmitters that transmit pain impulses

Answer 12

• Nociceptin: hypothalamus and brainstem
• substance p : spinal cord
• glutamate: dominant in acute pain

Question 13

Name 3 neurotransmitters that suppress pain signals

Answer 13

• Serotonin
Opioids (in CNS: met-enkephalin, leu-enkephalin, dynorphin, beta-endorphin)
• glycine