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NEUROLOGY > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What are the various mechanisms that analgesics use to reduce pain?

A
  • act at site of injury to decrease nerve sensitisation
  • suppress nerve conduction
  • suppress synaptic transmission in dorsal horn
  • activate descending inhibitory controls
  • targeting ion channels upregulated in nerve damage
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2
Q

How do NSAIDs reduce nociception and pain at the injury site?

A
  • blocking synthesis of prostaglandins (PGE2 and PDE2)

- prostaglandins usually make afferent nerve terminal more sensitive to pain signals

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3
Q

How do local anaesthetics suppress nerve conduction to reduce pain and nociception?

A

blocking/inactivating voltage-activated Na+ channels

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4
Q

How do opioids and some anti-depressant drugs work to relieve pain and nociception?

A
  • suppress synaptic transmission of nociceptive signals in dorsal horn of the spinal cord
  • activate descending inhibitory controls
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5
Q

What are the three levels on the WHO analgesic ladder and give an example of drugs in each level.

A

3) STRONG opioid (e.g. morphine, oxycodone, heroin, fentanyl)
2) WEAK opioid (e.g. codeine, tramadol)

1) NSAIDs (e.g. aspirin, diclofenac, ibuprofen, naproxen)
+ paracetamol

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6
Q

What levels of the WHO ladder are appropriate to combine?

A

1+2
1+3

Don’t combine 2 and 3 as these act on ame receptors => combination makes little difference

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7
Q

WHat is the difference between Opiates and Opioids?

A

Opiates - substances extracted from opium

Opioids - any agent acting on opioid receptors (including substances made in the body)

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8
Q

What is Supraspinal anti-nociception?

A

Descending controls which are modifying th eperception of pain and nociception

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9
Q

What areas of the brain are involved in Supraspinal anti-nociception?

A
  • parts involved in pain perception and emotion
    => cortex, amygdala, thalamus, hypothalamus
    These project signals to specific brainstem nuclei
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10
Q

WHat areas of the brainstem are involved in creating the efferent signals to the spinal cord (which will eventually modify afferent inputs)?

A
  • the periaqueductal grey matter (PAG) (midbrain)
  • locus ceruleus (pons)
  • nucleus raphe magnus (NRM) (medulla)
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11
Q

Excitation of the PAG in the brainstem by what two components has the potential to inhibit nociceptve transmission in the spinal cord?

A

Electrical signals from neurones or by opioids (these can even be endogeneous)

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12
Q

After its own excitation, PAG excites the NRM in the medulla to send signals along what neurones?

A

serotonergic and enkephalinergic neurones (=> ones releasing serotonin (5HT) and enkephalins)

These project to the dorsal horn resulting in nociceptive suppression

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13
Q

What type of receptor is the opioid receptor?

A

G protein-coupled receptors

signal to Gi or Go

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14
Q

What are the main functions of binding to the opioid receptor?

A
  • Prevent neurotransmitter release (less Ca2+ intake)

- hyperpolarise post synaptic terminal => less likely APs

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15
Q

What are the main classifications of opioid receptor?

A

μ - responsible for most opioid analgesic action
- BUT these can have major adverse effects

δ - contributes to analgesia but can cause convulsion

κ - contributes to analgesia at spinal and peripheral level
- activation associated with sedation, dysphoria and hallucinations

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16
Q

What is the main adverse effect of opioids?

A

Respiratory depression

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17
Q

Morphine can be used for both acute severe pain and chronic pain. TRUE/FALSE?

A

TRUE

18
Q

Describe how morphine is metabolised?

A
  • metabolised in the liver at positions 3 and 6 on molecule
  • yields M3G that is inactive
  • also yields M6G which retains analgesic activity and is excreted by the kidney
19
Q

Give an example of immediate and sustained release preparations of morphine

A 
Immediate (e.g. Oramorph)
Sustained release (e.g. MST Continus)
20
Q

How long do sustained release morphine preparations usually last for?

A

12-24 hours

21
Q

What opioids are agonists of the opioid receptor?

A 
AGONISTS:
morphine
heroin
Codeine
Fentanyl
Pethidine
Buprenorphine
Tramadol
Methadone
22
Q

What opioids are antagonists of the opioid receptor?

A 
Naloxone
Naltrexone (longer 1/2 life)
23
Q

What is diamorphine (heroin) used for clinically?

A
  • more lipophilic than morphine
    => when administered IV it enters CNS rapidly
    => can be used for severe post-operative pain
24
Q

How is codeine metabolised and what is it metabolised to?

A
  • hepatic metabolism to morphine
  • completed by CYP2D6 and CYP3A4
    => if patients have low levels of these, they may struggle to metabolise the drug to the active form
25
Q

How is codeine normally delivered?

A

Orally

26
Q

What other functions can codeine have?

A

anti-diarrhoeal (opiates cause constipation)

antitussive activity => relieves cough

27
Q

When is fentanyl used?

A
  • Given IV during some surgeries to reduce the amount of general anaesthetic required
  • Transdermal patches used in chronic pain
28
Q

How much more potent is fentanyl than morphine?

A

75-100 times more potent

29
Q

When is Pethidine used for pain, and how is it delivered?

A
  • acute pain, particularly labour
  • short duration of action => not suitable for chronic pain
  • Given IV, IM, or SC
30
Q

What drug class should not be given in combination with Pethidine and why?

A

MAO inhibitors (powerful antidepressant)

Combination causes excitement, convulsions, hyperthermia

31
Q

What is buprenorphine used for and how is it given?

A
  • chronic pain with patient-controlled injection systems
  • may have slow onset, but used due to long duration of action
  • Given by injection or sublingually
32
Q

Tramadol should be avoided in what group of patients?

A

Epileptic patients

33
Q

What is methadone used for, and why is it helpful that the half life is long?

A
  • assists in withdrawal from ‘strong opioids’ e.g. heroin
  • short acting opioids = more addictive => this helps patients to withdraw
  • given orally
  • long duration of action also useful in treating patients with chronic pain in terminal cancer
34
Q

Naloxone is an antagonist at which of the opioid receptors?

A

antagonist at μ-receptors

35
Q

When is naloxone used?

A
  • reverse opioid toxicity associated with ‘strong opioid’ overdose
  • may be given to a newborn with opioid toxicity due to administration of pethidine to mother during labour
36
Q

Why is the short half life of naloxone impractical if a patient has opioid toxicity?

A
  • may need frequent dosing of naloxone to completely reverse toxicity (=> dont leave patient)
  • beware of opioid addicts as short duration of naloxone may trigger a very acute withdrawal response
37
Q

What are the side effects of NSAIDs and COX-2 inhibitors?

A

NSAIDs - gastrointestinal damage

COX-2 - prothrombotic

38
Q

What conditions can cause neuropathic pain?

A
  • trigeminal neuralgia
  • diabetic neuropathy
  • post-herpetic neuralgia
  • phantom limb pain
39
Q

How do neuropathic pain drugs such as Gabapentin and pregabalin act to reduce pain and nociception?

A
  • reduce expression of a subunit (α2δ) of some voltage-gated Ca2+ channels
  • These channels are upregulated in damaged sensory neurones => release more neurotransmitter/signals

=> less upregulated channels = decrease of neurotransmitters (glutamate and substance P) from nociceptive neurones

40
Q

Hod do tricyclic antidepressants aim to deal with neuropathic pain?

A
  • E.g. Amitriptyline, nortriptyline
  • act centrally by decreasing the reuptake of noradrenaline
  • duloxetine and venlafaxine also decrease reuptake of 5-HT
41
Q

What drug is used to control pain in trigeminal neuralga and how does it achieve this?

A

Carbemazepine

  • blocks subtypes of voltage-activated Na+ channel that are upregulated in damaged nerve cells
  • prevents number of attacks in TN

NEUROLOGY (29 decks)

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