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BDS3 - Oral Surgery > Analgesia Part 2 > Flashcards

Analgesia Part 2 Flashcards

1
Q

what do NSAIDs do

A

• Inhibit cyclo-oxygenases and so reduce prostaglandins (which sensitise the tissues to other inflammatory mediators resulting in pain)

• The NSAIDs (aspirin and ibuprofen) inhibit COX-1 and COX-2
○ Predominantly COX-1 inhibition
○ Aspirin is 150 times more effective at inhibiting COX-1 than COX-2

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2
Q

what is COX-1 / what does it do

A

COX-1 is the cyclo-oxygenase predominantly responsible for catalysing the reaction that produces prostaglandins associated with:
○ Platelet aggregation
○ Protection of the gastric mucosa

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3
Q

what is COX-2 / What does it do

A

COX-2 is the enzyme responsible for the generation of the inflammatory prostaglandins
Although in some situations COX-1 is also involved

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4
Q

the amount of aspirin needed to have sufficient anti-inflammatory effects by inhibition of COX-2 will cause what

A

Amount of aspirin needed to have sufficient anti-inflammatory effects by inhibition of COX-2 will cause gastric damage due to the amount of COX-1 inhibition

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5
Q

what does the action of the formed prostaglandins depend on

A

○ The pathological situation
○ Whether they are formed by COX-1 or COX-2
○Whether they are formed in excessive amounts

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6
Q

what is generated in low physiological amounts by COX-1 and what does this do

A

PGE2 is generated in low physiological amounts by COX-1 in gastric tissues and has a protective effect

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7
Q

when are prostaglandins generated in excessive amounts

A

Prostaglandins (especially PGE2) are generated in excessive amounts during inflammation via elevated COX-2 levels

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8
Q

what does PGE2 in large amounts produce

A

PGE2 in large amounts produces increased vasodilation, increased vascular permeability and sensitises pain fibre nerve endings to bradykinin, 5HT and other mediators

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9
Q

why does it make sense to have COX-2 selectives

A

Since the analgesic actions of NSAIDs appear to result from the inhibition of COX-2 (mainly, although COX-1 may be involved) it would make sense to have selective COX-2 inhibitors and spare COX-1
Therefore less gastric effect

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10
Q

are cox-2 inhibitors associated with a higher or lower risk of serious upper GIT side effects compared with non-selective NSAIDs

A

selective COX-2 Inhibitors are associated with a lower risk of serious upper GIT side effects compared with non-selective NSAIDs

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11
Q

what is celecoxib and what does it do

A

selective cox-2 inhibitor
Useful anti-inflammatory actions and fewer GIT damaging actions compared with non-selective NSAIDs

Note: this view may be too simplistic
Some data suggests that COX-2 generated prostaglandins may also contribute to gastric mucosal integrity and damage repair

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12
Q

what patients are all NSAIDs including COX-2 inhibitors contraindicated in

A 
All NSAIDs (including selective COX-2 Inhibitors) are contraindicated in patients with active peptic ulceration
Non-selective NSAIDs are contraindicated in patients with a history of peptic ulceration
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13
Q

what does the BNF recommend with regards to NSAIDs

A

do not use more than one oral NSAID at a time (including selective COX-2 inhibitors)

Regarding dental and orofacial pain - COX-2 selectives should be chosen to manage dental pain only in patients at high risk of gastric or duodenal ulceration (eg those with a history of peptic ulcer)

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14
Q

why are selective cox-2 inhibitors thought to be better tolerated by patients with clotting disorders

A

Highly selective COX-2 inhibitors do not have an effect on platelet aggregation and so many be better tolerated by patients with clotting disorders

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15
Q

what is another name for paracetamol

A

Acetaminophen

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16
Q

is paracetamol an NSAID

A

Paracetamol is traditionally included under the banner of NSAIDs although in reality it is a simple analgesic without anti-inflammatory activity

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17
Q

what are the properties of paracetamol

A
  • Analgesic
  • Antipyretic
  • Little or no anti-inflammatory action
  • No effects on bleeding time
  • Does not interact significantly with warfarin
  • Less irritant to GIT
  • Suitable for children
  • Relatively safe analgesics ~ very commonly used
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18
Q

explain the mode of action of paracetamol

A
  • Hydroperoxides are generated from the metabolism of arachidonic acid by COX and exert a positive feedback to stimulate COX activity
  • This feedback is blocked by paracetamol, thus indirectly inhibiting COX - especially in the brain

• Results in:
○ Analgesia
○ Antipyretic action
○ No reduction in peripheral inflammation

• A small component of the analgesic action of all NSAIDs is the reduction of prostaglandins in the pain pathways of the central nervous system, such as in the thalamus
○ This is the main site of action of paracetamol

  • Alternative central mechanisms have also been proposed including reduced 5HT production or interference with the excitatory amino acid NMDA (N-Methyl-D-Aspartate) in spinal cord pathways
  • Exact mode of action still unclear
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19
Q

why does paracetamol cause only little / no gastric mucosal irritation

A

Since it does not appear to have much effect on peripheral prostaglandins there is little / no gastric mucosal irritation

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20
Q

is paracetamol a safe analgesic

A

It is described as a ‘safe analgesic’ although it causes severe problems in overdose

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21
Q

when do you need to take caution when prescribing paracetamol

A
  • Hepatic impairment
  • Renal impairment
  • Alcohol dependence
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22
Q

what are the side effects of paracetamol

A

these are rare

  • rashes
  • Blood disorders
  • Hypotension reported on infusion ~Reduced blood pressure particularly if given IV
  • Liver damage (and less frequently kidney damage) following overdose
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23
Q

what does paracetamol interact with

A

• Anticoagulants
○ Prolonged regular use of paracetamol possibly enhances the anticoagulant effects of the coumarins
○ Fairly minimal

  • Cytotoxics
  • Domperidone
  • Lipid-regulating drugs
  • Metoclopramide
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24
Q

how should you recommend odontogenic pain should be managed with paracetamol

A

For mild to moderate odontogenic or post-operative pain, an appropriate 5-day regime:

• Paracetamol tablets, 500mg
Send: 40 tablets
Label: 2 tablets 4x daily

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25
Q

what are the dosages recommended for children with paracetamol

A

For children: paracetamol tablets or soluble tablets, 500mg or oral suspension 120mg/5 ml or 250 mg/5 ml

○ 6months-2 years = 120mg 4x daily (max. 4 doses in 24 hours)

○ 2-4 years = 180mg 4x daily (max. 4 doses in 24 hours)

○ 4-6 years = 240mg 4x daily (max. 4 doses in 24 hours)

○ 6-8 years = 250mg 4x daily (max. 4 doses in 24 hours)

○ 8-10 years = 375mg 4x daily (max. 4 doses in 24 hours)

○ 10-18 years = 500mg 4x daily (max. 4 doses in 24 hours)

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26
Q

what advice should be given to patients regarding the dose of paracetamol

A

Advise patient that paracetamol can be taken at 4-hourly intervals but not to exceed the recommended daily dose
○ Maximum 4g for adults

• Overdose with paracetamol is dangerous because it can cause hepatic damage that is sometimes not apparent for 4-6 days
○ As little as 10-15g taken within 24 hours can cause severe hepatocellular necrosis
○ Transfer patients who have taken an overdose to hospital

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27
Q

what is the maximum dose of paracetamol for adults

A

Maximum dose = 4g daily (8 tablets

Always warn patient with regard to maximum dose and emphasise that they should not exceed this

28
Q

what is the maximum dose of paracetamol for children

A

Depends on weight / age

See BNF

29
Q

what are the side effects of overdose

A

As little as 10-15g (20-30 tablets) or 150mg/Kg of paracetamol taken with 24 hours may cause severe hepatocellular necrosis, and less frequently, renal tubular necrosis

• Anorexia, nausea, vomiting
○ Only early features of poisoning
○ Usually settle within 24 hours

  • Persistence of these features beyond 24 hours is often associated with abdominal pain: right subcostal pain and tenderness, usually indicates development of hepatic necrosis
  • Liver damage is maximal at 3-4 days after ingestion and may lead to jaundice, renal failure, haemorrhage, hypoglycaemia, encephalopathy, cerebral oedema and death

Therefore, despite a lack of significant early symptoms, patients who have taken an overdose of paracetamol should be transferred immediately to hospital

30
Q

what is the name of teh opioid analgesia in the dental practitioners forumulary

A

Dihydrocodeine

31
Q

where does opioid analgesics act

A

Act in the spinal cord
Especially in the dorsal horn pathways associated with paleo-spinothalamic pathway
Ie act centrally on opioid receptors

32
Q

opioid analgesia causes central regulation of pain in what

A

○ Periaqueductal grey matter
○ Nucleus reticularis paragigantocellularis
○ Raphe magnus nucleus

33
Q

how do opioid receptors produce their effects

A

They produce their effects via specific receptors which are closely associated with the neuronal pathways that transmit pain to the CNS

34
Q

what is opioid a term used for

A

Opioid is a term used for both naturally occurring and synthetic molecules that produce their effects by combining with opioid receptors

35
Q

are opioid analgesics useful for dental pain

A

Opioid analgesics are relatively ineffective in dental pain

36
Q

what are the problems with opioid analgesics

A

• Dependence
○ Psychological and physical
○ Withdrawal of the drug will lead to psychological cravings and the patient will also be physically ill

• Tolerance - only to depressant effects
○ As the body becomes more tolerant to the drug the patient is going to require more and more to get the same effect
○ To achieve the same therapeutic effects the dose of the drug needs to be progressively increased

• Effects on smooth muscle:
○ Constipation
§ Can occur after few doses of dihydrocodeine
○ Urinary and bile retentiob
○ Long term can make patients uncomfortable

37
Q

what effect does opioid analgesics have on the CNS

A 
• Depresses
○ Pain centre ~ Alters awareness / perception of pain
○ Higher centres
○ Respiratory centre
○ Cough centre ~Cough suppression
○ Vasomotor

• Stimulate
○ Vomiting centre ~ Dihydrocodeine often causes nausea and vomiting which limits it value in dental pain [If they cannot ingest the drug then they are not going to absorb very much of the drug]
○ Salivary centre
○ Pupillary constriction

38
Q

What are the common side effects of opioids

A

○ Nausea
○ Vomiting
○ Drowsiness
○ Larger doses produce respiratory depression and hypotension

39
Q

what are the other side effects of opioids

A 
○ Difficulty with micturition 
○ Ureteric or biliary spasm
○ Dry mouth
○ Sweating 
○ Facial flushing
○ Headache 
○ Vertigo
○ Bradycardia
○ Tachycardia 
○ Palpitations 
○ Postural hypotension
○ Hypothermia 
○ Hallucinations 
○ Dysphoria 
○ Mood changes
○ Dependence 
○ Miosis
○ Decreased libido or potency 
○ Rashes / urticaria / pruritis
40
Q

what enhances the effects of opioids

A

effects of opioids enhanced by alcohol

41
Q

what are the cautions with opioid use

A 
• Hypotension
• Hypothyroidism 
• Asthma 
• Decreased respiratory reserve
• Prostatic hyperplasia 
• Pregnancy / breast-feeding
• May precipitate coma in hepatic impairment
	○ Reduce dose or avoid
• Renal impairment
	○ Reduce dose or avoid
	○ Cannot excrete the drug fully
• Elderly and debilitated 
	○ Reduce dose
	○ Considerable reduction in dose if it is needed
• Convulsive disorders
• Dependence
42
Q

what are the contraindications to opioid use

A
  • Acute respiratory depression
  • Acute alcoholism

• Raised intracranial pressure / head injury
○ Interferes with respiration
○ Affects pupillary responses vital for neurological assessment

43
Q

what is codeine

A

A natural alkaloid found in opium poppy

1/12th the potency of morphine

44
Q

what are the properties of codeine

A
  • Effective orally
  • Low dependence

• Usually in combination with NSAIDs or paracetamol
○ Eg co-codamol ~ this is over the counter
§ 8mg codeine
§ 500mg paracetamol
○ 30mg codeine and 500mg paracetamol is prescription only formula but we cannot prescribe as dentists

  • Effective cough suppressant
  • Available over the counter
45
Q

what is a common side effect of codeine

A

Common side effect = constipation

46
Q

is codiene availalble on teh dental list

A

Codeine phosphate not on dental list

The only codeine combination on the dental list is dihydrocodeine

47
Q

what is dihydrocodeine known as

A 
Dihydrocodeine Tartrate
DF118 Forte (trade name)
48
Q

what is the potency of dihydrocodeine

A

Potency similar to codeine

49
Q

what routes can dihydrocodeine be taken

A

SC (subcutaneous) or IM (intra-muscular) = controlled drug

Oral (tablet form) = not controlled

50
Q

what is the dose of dihydrocodeine

A

Oral: 30mg every 4-6 hours as necessary
(40, 60, 120mg tablets are not available on the Dental List)
Oral is the only route on the dental list

51
Q

what are the side effects of opioids

A

The same as general opioids side effects:
• Nausea / vomiting
• Constipation
• Drowsiness

Larger doses:
	• Respiratory depression
	• Hypotension
	• Ureteric spasm
	• Biliary spasm
	• Many more
52
Q

what are dihydrocodeine interactions

A

many ~ see BNF

serious interactions =
• Antidepressants MAOIs
• Dopaminergics (Parkinsonism)

53
Q

what are the cautions of dihydrocodiene

A 
Same as general opioid cautions:
	• Hypotension
	• Asthma
	• Pregnancy / lactation
	• Renal / hepatic disease
	• Elderly / children
Never prescribe in raised intracranial pressure / suspected head injury
54
Q

when is dihydrocodeine used

A

○ Moderate to severe pain
○ However BNF states that due to the side effects of nausea and vomiting it is of little value for dental pain
○ Not very effective for post-operative dental pain

55
Q

what can overdose of opiods cause

A
  • Opioids cause varying degrees of coma, respiratory depression, & pinpoint pupils
  • The specific antidote Naloxone is indicated if there is coma or bradypnoea

• Naloxane has a shorter duration of action than many opioids
○ Therefore close monitoring and repeated injections / infusion may be necessary according to respiratory rate and depth of coma

56
Q

what are the different types of neuropathic and functional pain in dental treatment

A

○ Trigeminal neuralgia
○ Post-herpetic neuralgia
○ Functional: TMJ or atypical facial pain

57
Q

what drug on the dental list can treat neuropathic and functional pain

A

• At present the only drug on the dental list is carbamazepine
○ Proprietary band eg Tegretol
○ Anti-convulsant [Emergency drug for epilepsy]
○ Can also be used to control trigeminal neuralgia

58
Q

what drugs can treat trigeminal neuralgia

A

• Carbamazepine on dental prescribers’ formulary

• Other drugs used for trigeminal neuralgia include:
○ Gabapentin
○ Phenytoin
At present these are not included on the dental list

59
Q

what are the clinical features of trigeminal neuralgia

A

○ Severe spasms of pain
§ ‘electric shock’
§ Lasts seconds

○ Usually unilateral

○ Older age group

○ Trigger spot identified
§ Triggers could be washing face or cold wind hitting face
§ Recurrence of symptoms usually means greater severity

○ Females more than males

○ Periods of remission

○ Recurrences often greater severity

○ Tends to only affect one branch of the trigeminal nerve but can affect more

60
Q

how would you prescribe carbamaxepine to treat trigeminal neuralgia

A

○ 100 or 200mg tablets

○ Starting dose 100mg once or twice daily
§ But some patients may require higher initial dose

○ Increase gradually according to response of patient
§ Step ladder increasing dose

○ Usual dose: 200mg 3-4x daily
§ Up to 1.6g daily in some patients

○ Maintenance dose = 200mg 3-4x daily

○ Maximum dose = 1.6g daily

61
Q

what are the side effects of carbamazepine

A 
Extensive list - see BNF
• Dizziness 
• Ataxia 
• Drowsiness
	○ As it is usually prescribed to older patients want to be wary of this as it might mean an increased risk of falls
• Leucopenia and other blood disorders
62
Q

how is needed if a patient is on carbamzepine

A

Patient blood monitoring needed

  • Blood count
  • Liver function tests
  • As a minimum these tests should be asked for to get a baseline to see if there are any pre-existing issues before the patient starts this drug
63
Q

what are contrainidcations of carbamazepine

A

• AV conduction abnormalities
○ Unless paced
• History of bone marrow depression
• Porphyria

64
Q

what are the cautions of prescribing carbamazepine

A
  • Hepatic / renal / cardiac disease
  • Skin reactions
  • History of haematological reactions to other drugs
  • Glaucoma
  • Pregnancy / breast-feeding
  • Avoid abrupt withdrawal
65
Q

what are the 6 analgesic drugs to be familiar with in the dental practitioners formulary

A
  • Aspirin (NSAID)
  • Ibuprofen (NSAID)
  • Diclofenac (NSAID)
  • Paracetamol
  • Dihydrocodeine (opioid)
  • Carbamazepine

BDS3 - Oral Surgery (7 decks)

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