Analgesia Flashcards
1
Q
What you need to know when prescribing analgesia?
A
- Choose a limited number drugs and know them well
- Mechanism of action
- Doses
- Side effects
- Interactions
- Groups of patients to avoid
2
Q
What is the Arachidonic Acid pathway?
A
- Tissue injury
- Leads to Injury to Phospholipid Cell membrane
- Phospholipase A2 released and causes release of arachidonic acid from phospholipid membrane
- Leads to two pathways
Pathway 1 - Cyclooxygenase Pathway (COX-1, COX-2)
- Lead to Prostaglandin G2 (PGG2)
- Lead to Prostaglandin H2 (PGH2)
- Lead to Prostacyclin/ Prostaglandin which causes pain, inflammation/ Thromboxane cause platelet aggregation
Pathway 2 - 5- Lipoxygenase Pathway
- Lead to Leukotrienes which cause bronchoconstriction, asthma attacks and smooth muscle contraction
3
Q
How do Prostaglandins cause pain?
A
- Do not cause pain directly but
- Sensitise tissues to other inflammatory products such as leukotrienes
- If prostaglandin production decreases, this will moderate pain
4
Q
What is Aspirin?
A
- NSAIDs drug
- Effective for dental and TMJ pain
- Superior anti-inflammatory properties to paracetamol
- Less common in dentistry as Ibuprofen more common
- Can be bought over counter
5
Q
What are the Properties of Aspirin (Acetylsalicylic acid)?
A
- Analgesic
- Antipyretic
- Anti-inflammatory
- Metabolic
6
Q
What is the mechanism of action for Aspirin?
A
- Aspirin inhibits cyclo-oxygenases (COX-1 and 2)
- Therefore reduces production of Prostaglandin
- More effective at inhibiting COX-1
- COX-1 inhibition reduces platelet aggregation (predisposes to damage of gastric mucosa)
7
Q
What are Aspirins Analgesic Properties?
A
- Analgesic action of NSAIDs exerted both peripherally and centrally
- Peripheral actions predominate
- Analgesic action results from inhibition of prostaglandin synthesis in inflamed tissues (Cyclo-oxygenase inhibition)
8
Q
What are the Antipyretic properties of Aspirin?
A
- Aspirin prevents temperature raising effects of interleukin-1 and rise in brain prostaglandin levels
- So reduces elevated temperature in fever
- Doesn’t reduce normal temp
9
Q
What are the Anti-inflammatory properties of Aspirin?
A
- Prostaglandins are vasodilators therefore affect capillary permeability
- Aspirin good anti-inflammatory
- Reduces redness and swelling as well as pain at site of injury
10
Q
What are some problems with Aspirin?
A
- Adverse/side effect
- Groups to avoid
- Caution when prescribing
11
Q
What are some adverse effects of Aspirin?
A
- GIT problems
- Hypersensitivity
- Overdose (tinnitus, metabolic acidosis)
- Aspirin burns (mucosal)
12
Q
What is metabolic acidosis?
A
- Condition where excess acid in bodily fluids
- Causes rapid breathing, confusion, tiredness, headache, jaundice and increased heart rate
13
Q
What are the GIT problems associated with Aspirin?
A
- Mostly on mucosal lining of stomach
- Prostaglandins (PGE2 and PGI2)
- Inhibit gastric acid secretion
- Increase blood flow through gastric mucosa
- Help production of mucin by cells in stomach lining (cytoprotective action)
14
Q
Why do you need to take care with patients with GIT problems when prescribing aspirin?
A
- Patients may have ulcers or Gastro-oesophageal reflux
- Most pt taking aspirin will suffer some blood loss from GIT (not detectable macroscopically and asymptomatic)
15
Q
What reactions can occur with hypersensitivity adverse effects of apsirin?
A
- Acute bronchospasm/ asthma type attacks
- Skin rashes / urticaria/ angiodema
- Other allergies
- Take care when prescribing to asthmatics
16
Q
What can happen during overdose of aspirin?
A
- Hyperventilation
- Tinnitus, deafness
- Vasodilatation & sweating
- Metabolic acidosis (can be life threatening)
- Coma (Uncommon)
17
Q
What can happen during mucosal burn adverse effect of Aspirin?
A
- Direct effect of salicylic acid
- Aspirin applied locally to oral mucosa results in a chemical burns
- Aspirin has no topical effect.
*Ensure aspirin taken with water
18
Q
What groups should you avoid/ caution when prescribing Aspirin?
A
- Peptic Ulceration
- Epigastric pain
- Bleeding abnormalities e.g. Haemophilia
- Anticoagulants
- Pregnancy/breast-feeding
- Patients on steroids
- Renal/Hepatic impairment
- Children & Adolescents under 16 years
- Asthma
- Hypersensitivity to other NSAIDs
- Taking other NSAIDs
- Elderly
- G6PD-deficiency
19
Q
Why should you avoid groups with peptic ulceration when prescribing aspirin?
A
- Gastric or duodenal ulcer could result in perforation in people with peptic ulcer disease
20
Q
Why should you avoid groups with Epigastric pain when prescribing aspirin?
A
When History of epigastric pain / discomfort or gastro-oesophageal reflux but no ulcer diagnosed
21
Q
Why avoid prescribing Aspirin when patients taking Anticoagulants?
A
- Aspirin enhances warfarin and other coumarin anticoagulants
- Displaces warfarin from binding sites on plasma proteins
- Increases free warfarin
- The majority of warfarin is bound (inactive). If more is released this will become active increasing bleeding tendency
22
Q
Why avoid prescribing Aspirin in groups who are pregnant/lactation?
A
- Especially 3rd trimester:
- This is nearer delivery and may cause impairment of platelet function:
- Increased risk of haemorrhage
- Increased risk of jaundice in baby
- Can prolong/delay labour (don’t know why)
(contraindicated in breastfeeding – Reye’s syndrome)
23
Q
Why avoid prescribing Aspirin for patients on steroids?
A
- Approx. 25% of patients on long term systemic steroids will develop a peptic ulcer
- If they have an undiagnosed ulcer, Aspirin may result in perforation
24
Q
Why avoid prescribing Aspirin for patients with Renal/ Hepatic impairment?
A
- Aspirin metabolised in liver and excreted mainly in the kidney
- If renal impairment - excretion may be reduced/delayed
- Not a complete contraindication but administer with care/reduce dose and avoid if renal or hepatic impairment severe
25
What is Nephrotoxicity?
- Prostaglandins PGE2 and PGI2 are powerful vasodilators
- PGE2 synthesised in renal medulla
- PGI2 synthesised in glomeruli
- Both involved in control of renal blood flow and excretion of salt and water
- Inhibition of renal prostaglandin synthesis may result in;
- sodium retention
- reduced renal blood flow
- renal failure,
- NSAIDs may cause interstitial nephritis and hyperkalaemia.
26
Why should you avoid prescribing Aspirin to Children and Adolescents under 16years?
- Can cause Reye's syndrome which is very serious with up to 50% mortality
- Avoid during fever or viral infections in adolescents
27
What is Reye's Syndrome?
- Very rare
- Fatty degenerative process in liver
- Profound swelling in brain
- Can lead to liver damage and Encephalopathy
- Mortality rate 50% related to brain damage due to encephalopathy
28
Why should you avoid/caution patients with Asthma when prescribing Aspirin?
- NSAIDs not completely contraindicated as some asthmatics have no problem with them
- Ask the patient if they have used them before and if any problems
29
Why should you avoid patients with hypersensivity to other NSAIDs?
- Contraindicated in patients with history of hypersensitivity to Aspirin or any other NSAIDs
- Using a combo of NSAIDs will increase the risk of side effects
30
Why should elderly groups be avoided/cautioned when prescribing Aspirin?
- Elderly more susceptible to drug induced side effects in general
- They often smaller/ smaller circulating blood volume
- On other medications
- Have other medical problems
31
What deficiency should be avoided/cautioned when prescribing Aspirin?
- Glucose 6-phosphate dehydrogenase deficiency prevalent in individuals originating from parts of Africa/ Asia/ Oceana/ Southern Europe
- More susceptible to developing acute haemolytic anaemia on taking number of common drugs
- Aspirin carries poss risk of haemolysis in some deficient individuals
- Acceptable up to dose of at least 1g daily in most deficient individuals
32
What groups is Aspirin completely contraindicated in?
1. Children & Adolescents under 16 years; breast feeding (Reye’s Syndrome)
2. Previous or active peptic ulceration
3. Haemophilia
4. Hypersensitivity to Aspirin or any other NSAID
33
How does Ibuprofen effect gastric mucosa?
- Irritant to gastric mucosa but lower risk than aspirin
34
Why should you take care when prescribing Ibuprofen for asthmatics?
- May cause bronchospasm but not completely contraindicated
35
What is the max adults does of Ibuprofen?
- 2.4g
36
What groups should you take caution with Ibuprofen?
- Previous or active peptic ulceration
- The Elderly
- Pregnancy & lactation
- Renal, cardiac or hepatic impairment
- History of hypersensitivity to Aspirin & other NSAIDs
- Asthma
- Patient taking other NSAIDs
- Patients on long term systemic steroids
37
What are the side effects of Ibuprofen?
- GIT discomfort, occasionally bleeding & ulceration
- Hypersensitivity reactions e.g. rashes, angioedema & bronchospasm
- Others: headache, dizziness, nervousness, depression, drowsiness, insomnia, vertigo, hearing disturbance/tinnitus, photosensitivity, haematuria, blood disorders, fluid retention, renal impairment, hepatic damage, pancreatitis, eye changes, Stevens-Johnson syndrome & others (see BNF)
38
What are the potential drug interactions of Ibuprofen?
- ACE Inhibitors
- Other Analgesics
- Antibiotics
- Anticoagulants
- Antidepressants
- Antidiabetics
- Corticosteroids
- Cytotoxics
- Diuretics
- Beta-blockers
- Calcium-channel blockers
- Cardiac glycosides
- Ciclosporin
- Clonidine
- Clopidogrel (an antiplatelet drug)
- Lithium
- Tacrolimus
- Vasodilator Antihypertensives
(CHECK BNF)
39
What are the symptoms and treatment for Ibuprofen overdose?
- Nausea
- Vomiting
- Tinnitus (more serious toxicity very uncommon)
Activated charcoal followed by symptomatic measures are indicated if more than 400mg/kg has been ingested within the preceding hour.
40
What is paracetamol?
- AKA Acetaminophen
- Simple analgesic without anti-inflammatory activty
41
What are the benefits of Paracetamol?
- 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
42
What is the mode of action of Paracetamol?
- 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
43
What does Paracetamol mode of action result in?
- Analgesia
- Antipyretic action
- No reduction in peripheral inflammation
44
Where is the main site of action of Paracetamol?
- Reduction of prostaglandin in pain pathways of CNS, in thalamus
45
What is the alternative central mechanism for mode of action of Paracetamol?
- Reduced 5HT production
- Interference with the excitatory amino acid NMDA (N-Methyl-D-Aspartate) in spinal cord pathways
Exact mode of action still unclear
46
What cautions should take when prescribing Paracetamol?
- Hepatic impairment
- Renal impairment
- Alcohol dependence
47
What are the side effects of Paracetamol?
- Rare but can still occur
- Rashes
- Blood disorders
- Hypotension reported on infusion
- Liver damage (and less frequently kidney damage) following overdose
48
What drugs interact with Paracetamol?
- Anticoagulants (prolonged regular use of Paracetamol possibly enhances the anticoagulant effects of the coumarins)
- Cytotoxics
- Domperidone
- Lipid-regulating drugs
- Metoclopramide
49
What is the dosage of Paracetamol?
500mg tablets
- Adults: 1-2 tablets (0.5-1g) 4-6 hourly
Max. Dose: 4g daily (8 tablets)
- Children: Depends on weight/age – see BNF
Always warn patients of max dose and not to exceed this
50
What can happen if a patient has an overdose of Paracetamol?
- 10-15g (20-30 tablets) or 150mg/kg taken within 24hrs may cause severe hepatocellular necrosis, and less frequently, renal tubular necrosis
- Liver damage maximal at 3-4 days after ingestion - lead to liver failure then death
- Transfer to hospital immediately
51
How do opioid analgesics work?
- Act on spinal cord esp in dorsal horn pathways
- Central regulation of pain
- Produce their effects via specific receptors which are closely associated with the neuronal pathways that transmit pain to the CNS
BNF -'Opioid analgesics are relatively ineffective in dental pain'
52
What are some examples of Opioids?
- Fentanyl (extremely potent)
- Morphine
- Tramadol
- Codeine (weak)
53
What problems can arise from Opioid Problems?
Psychological and Physical Dependence - Withdrawal of the drug will lead to psychological cravings and the patient will also be physically ill
Tolerance - To achieve the same therapeutic effects the dose of the drug needs to be progressively increased
- Constipation (can occur after just a few doses)
- Urinary & bile retention
54
How do Opioid Analgesics effect CNS?
Depresses;
- Pain centre (alters awareness/perception of pain)
- Higher centres
- Respiratory centre
- Cough centre
55
What are the side effects of Opioids?
- Nausea, vomiting & drowsiness
- Larger doses produce respiratory depression & hypotension
- Dry mouth
- Hallucinations
- Sweating
- Dysphoria
- Facial flushing
- Mood changes
- Headache
- Dependence
- Vertigo
- Bradycardia
- Tachycardia
- Rashes/Urticaria/Pruritis
- Palpitations
56
What groups should you caution when prescribing Opioids?
- Hypotension
- Hypothyroidism
- Asthma
- Decreased respiratory reserve
- Pregnancy/Breast-feeding
- May precipitate coma in hepatic impairment (reduce dose or avoid)
- Renal impairment (reduce dose or avoid)
- Elderly & debilitated (reduce dose)
- Convulsive disorders
- Dependence
57
What are some contraindications of Opioids?
- Acute respiratory depression
- Acute alcoholism
- Raised intracranial pressure/head injury
- Interferes with respiration
- Affects pupillary responses vital for neurological assessment.
58
What is Codeine?
- A natural alkaloid found in opium poppy
- 1/12th the potency of morphine
- Effective orally
- Low dependence
- Usually in combination with NSAIDs or Paracetamol e.g. Co-codamol (8mg Codeine : 500mg Paracetamol)
- Effective cough suppressant
- Common side effect – constipation
- Available over the counter
59
What codeine combination is on the dental list?
- Dihydrocodeine
- Codeine phosphate is not
60
What is Dihydrocodeine?
- Potency similar to codeine
- Routes: SC / IM / Oral
- Only route on Dental List = Oral
- Oral Dose: 30mg every 4-6 hours as necessary
(40mg, 60mg, 120mg tablets not on the Dental List)
61
What are the side effects of Dihydrocodeine?
- Nausea/Vomiting
- Constipation
- Drowsiness
- Larger Doses: Respiratory depression, Hypotension, and many more
62
What are the two main drugs Dihydrocodeine interacts with?
- Antidepressants MAOIs
- Dopaminergics (Parkinsonism)
63
What groups should you caution when prescribing Dihydrocodeine?
- Hypotension
- Asthma
- Pregnancy/lactation
- Renal/Hepatic disease
- Elderly/Children
Remember: Never prescribe in raised intracranial pressure/suspected head injury
64
When should you use Dihydrocodeine?
- 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
- Patients look ill – very pale
- BNF also states that it is not very effective for post-operative dental pain
65
What can opioid overdose cause?
- Coma
- Respiratory depression
- Pinpoint pupils
66
What is the antidote for Opioid overdose?
- Naloxone if there is coma or bradypnoea
- Naloxone has a shorter duration of action than many opioids. Therefore, close monitoring and repeated injections/infusion may be necessary
67
What is included in the BNF category related to neuropathic and functional pain?
- Trigeminal neuralgia
- Post-herpetic neuralgia
- Functional – TMJ or Atypical facial pain
68
What drug can be used to control trigeminal neuralgia?
- Carbamazepine
- Proprietary brand e.g. Tegretol
- Anti-convulsant
- Gabapentin and Phenytoin can also be used but they are not on Dental List
69
What are the clinical features of Trigeminal Neuralgia?
- Severe spasms of pain: ‘Electric shock’, lasts seconds
- Usually unilateral
- Older age-group
- Trigger spot identified
- Females more than males
- Periods of remission
- Recurrences often greater severity
70
What is the dose of Carbamazepine for Trigeminal Neuralgia?
- 100 or 200 mg tablets
- Starting dose 100mg once or twice daily (but some patients may require higher initial dose)
- Increase gradually according to response
- Usual dose 200mg 3-4 times daily, up to 1.6g daily in some patients
