L69. Analgesia in Oral Surgery Flashcards
(67 cards)
1
Q
How does prostaglandin production effect perceived pain?
A
- Trauma/ infection lead to the breakdown of membrane phospholipids producing arachidonic acid;
- Arachidonic acid is broken down to form prostaglandins;
- Prostaglandins sensitise the tissues to other inflammatory products - pain;
- Reduction in prostaglandin production moderates pain.
2
Q
What type of analgesic is aspirin?
A
NSAID (non steroidal anti inflammatory drug)
3
Q
What is the active ingredient in aspirin?
A
Acetylsalicylic Acid
4
Q
What properties does aspirin offer?
A
- Analgesic;
- Antipyretic;
- Anti-inflammatory;
- Anti-platelet;
- Metabolic.
5
Q
What is the mechanism of action of aspirin?
A
- Reduces production of prostaglandins;
- Inhibits both COX-1 and 2 (150x more effective on COX-1);
- COX-1 inhibition reduces platelet aggregation and predisposes to damage of the gastric mucosa.
6
Q
How does aspirin work as an antipyretic?
A
- Prevents temperature raising effects of interleukin-1 and the rise in brain prostaglandin levels;
- This reduces elevation in temperature leading to a fever;
- Doesn’t reduce normal temperature.
7
Q
How does aspirin work as an anti-inflammatory?
A
- Inhibits prostaglandin production;
- Prostaglandins are vasodilators and effect capillary permeability;
- Reduces redness and swelling.
8
Q
What adverse side effects can be seen from aspirin?
A
- GIT problems;
- Hypersensitivity;
- Overdose: hyperventilation, vasodilation and sweating, tinnitus, metabolic acidosis, coma (uncommon);
- Aspirin burns - mucosal.
9
Q
How can aspirin cause GIT problems?
A
- Effects mucosal lining of the stomach;
- Prostaglandins (PGE2 and PGI2);
- Inhibit gastric acid secretion;
- Increase blood flow through the gastric mucosa;
- Help production of mucin by cells in stomach lining (cytoprotective action).
10
Q
How can aspirin cause mucosal burns?
A
Direct effect from salicylic acid when applied directly to mucosa (take with water!)
11
Q
What groups should be avoided when prescribing aspirin?
A
- GIT patients (previous or active peptic ulcers [risk of perforation!];
- Pregnant (especially third trimester) [can impair platelet function/ effect timing of labour];
- Breast feeding [Reye’s syndrome];
- Children and <16s [Reye’s syndrome];
- Hypersensitivity to aspirin or any other NSAIDs;
- Bleeding abnormalities (e.g. haemophilia);
- Anticoagulated patients [enhances warfarin/ coumarin anticoagulants by displacing warfarin binding sites and creating more free warfarin - increased bleeding tendency].
N.B. Normally, most warfarin is bound (inactive)
12
Q
Why groups should you be cautious about when prescribing aspirin?
A
- Asthmatics (ask if they’ve used NSAIDs before);
- Renal/ hepatic impairment [aspirin metabolised in liver and excreted by kidneys - either can be delayed with impairment - only a contraindication when impairment is severe];
- Patients on steroids (~25% of pts. on long-term steroids will develop a peptic ulcer, could be undiagnosed - risk of perforation);
- Patients with epigastric pain;
- Patients taking other NSAIDs [combination of NSAIDs will increase the risk of side effect, like seen in GIT];
- Patients with G6PD-deficiency [can develop acute haemolytic anaemia but up to 1g daily is usually acceptable in these patients];
- Elderly (more susceptible to drug-induced side effects in general due to smaller blood volume/ being on other medications/ medical problems).
13
Q
Why can aspirin effect asthmatics?
A
- Can cause hypersensitivity (acute bronchospasm/ asthma type attacks);
- Hypersensitivity can also lead to minor skin rashes/ other allergies.
14
Q
What is Reye’s syndrome?
A
- Fatty degenerative process in liver (and to a lesser extent in kidneys);
- Profound swelling in the brain;
- Clinically: initially nausea, vomiting, lethargy then seizures and coma later;
- Can lead to mortality (50%) due to brain damage by encephalopathy.
15
Q
What dose of aspirin should be prescribed for odontogenic pain?
A
- 300mg;
- 2 tablets, up to 4 times a day.
16
Q
What dose of aspirin should be given for thrombotic prophylaxis (cerebrovascular/ cardiovascular event)?
A
- Single dose of 150-300mg given ASAP;
- 75mg maintenance treatment.
17
Q
What drug is commonly prescribed with aspirin?
A
- Proton-pump inhibitor;
- e.g. Omeprazole 20mg, once a day;
- e.g. Lansoprazole 15mg, once a day.
18
Q
What property does ibuprofen not offer, that aspirin does?
A
Anti-platelet (less effect so not used therapeutically for this)
19
Q
What dose of ibuprofen should be prescribed for odontogenic pain/ post-operative pain?
A
- 400mg;
- 1 tablet, up to 4 times a day;
- After food.
20
Q
What is the maximum daily dose of ibuprofen for an adult?
A
2.4g
21
Q
Why groups should you be cautious about when prescribing ibuprofen?
A
- Previous or active peptic ulceration;
- The elderly;
- Pregnancy and lactation;
- Renal, cardiac or hepatic impairment;
- History of hypersensitivity to aspirin and other NSAIDs;
- Asthma;
- Patients taking other NSAIDs;
- Patients on long-term systemic steroids.
22
Q
What side effects can be seen from ibuprofen?
A
- GIT discomfort (occasionally bleeding and ulceration);
- Hypersensitivity reactions e.g. rashes, angioedema, bronchospasm;
- Others: headache, dizziness, nervousness, depression, drowsiness, insomnia, vertigo, haematuria, blood disorders, fluid retention, renal impairment, hepatic damage, pancreatitis, eye changes, Stevens-Johnson syndrome and others (see BNF).
23
Q
What drugs can ibuprofen potentially interact with?
A
- ACE inhibitors;
- Other analgesics;
- Antibiotics;
- Anticoagulants;
- Antidepressants;
- Antidiabetics;
- Corticosteroids;
- Cytotoxics;
- Diuretics;
- Beta-blockers;
- Calcium-channel blockers;
- Cardiac glycosides;
- Ciclosporin;
- Clonidine;
- Clopidogrel (anti-platelet drug);
- Lithium;
- Tacrolimus;
- Vasodilator antihypertensives;
- CHECK BNF.
24
Q
What are the symptoms of an ibuprofen overdose?
A
- Nausea;
- Vomiting;
- Tinnitus (more serious toxicity - very uncommon).
25
How is an ibuprofen overdose treated?
Activated charcoal followed by symptomatic measures are indicated if >400mg/kg has been ingested within the preceding hour
26
What does COX-1 do?
- Cyclo-oxygenase;
- Catalyses the reaction that produces prostaglandins associated with platelet aggregation and protection of the gastric mucosa.
27
What does COX-2 do?
- Cyclo-oxygenase;
| - Generation of most of the inflammatory prostaglandins (although in some situations COX-1 also involved).
28
What do the actions of prostaglandins depend on?
- The pathological situation;
- Whether they are formed from COX-1 or COX-2;
- Whether they are formed in excessive amounts.
29
Provide an example of a selective COX-2 inhibitor:
Celecoxib (Celebrex)
[used to treat the pain and inflammation in osteoarthritis, acute pain in adults, rheumatoid arthritis, ankylosing spondylitis, painful menstruation, and juvenile rheumatoid arthritis]
30
Why might a selective COX-2 inhibitor be chosen?
- COX-1 in gastric tissues release PGE2 (a prostaglandin) as a protective effect;
- COX-1 inhibition can have gastric effects (like aspirin);
- Are therefore contraindicated in patients with current or hx of peptic ulceration;
- Selective COX-2 inhibitors should be chosen to manage dental pain of patients at high risk of gastric or duodenal ulceration;
- These also have no effect on platelets so may be better tolerated by patients with clotting disorders.
31
What is the active ingredient in paracetamol?
Acetaminophen
32
Why is paracetamol not considered an NSAID?
No anti-inflammatory activity
33
What properties does paracetamol offer?
- 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.
34
What is the mechanism of action of paracetamol?
- Not fully known;
- 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;
- All NSAIDs reduce prostaglandin production of the CNS, such as the thalamus, but this is the main site for paracetamol;
- Results in analgesia and antipyretic action.
35
Why does paracetamol have little to no effect on gastric mucosal irritation?
Does not appear to have much effect on peripheral prostaglandin pathways
36
What groups should you be cautious about when prescribing paracetamol?
- Hepatic impairment;
- Renal impairment;
- Alcohol dependence.
37
What adverse side effects can be seen from paracetamol?
[rare!]
- Rashes;
- Blood disorders;
- Hyptension reported on infusion;
- Liver damage (and less frequently kidney damage), following overdose.
38
What drugs can paracetamol potentially interact with?
- Anticoagulants (prolonged regular use of paracetamol possibly enhances the anticoagulant effects of the coumarins);
- Cytotoxics;
- Domperidone;
- Lipid-regulating drugs;
- Metoclopramide.
39
What dose of paracetamol should be prescribed for odontogenic pain/ post-operative pain?
- 500mg;
| - 2 tablets, up to 4 times a day (every 4-6 hours).
40
What is the maximum daily dose of paracetamol for an adult?
4g (8 tablets)
41
What is classed as a paracetamol overdose?
- 10-15g (20-30 tablets);
- OR 150mg/kg, taken within 24 hours;
- May cause severe hepatocellular necrosis (and less frequently renal tubular necrosis).
42
What are the signs and symptoms of a paracetamol overdose?
1. Anorexia, nausea and vomiting (early features, usually settle within 24 hours);
2. Persistence of these beyond 24 hours is often associated with abdominal pain (usually indicates development of hepatic necrosis);
3. Liver damage is maximal at 3-4 days after ingestion and may lead to jaundice, renal failure, haemorrhage, hypoglycaemia, encephalopathy, cerebral oedema and death.
43
What should you do if you suspect a paracetamol overdose?
Immediate hospital referral
44
What opioid analgesia can dentists prescribe?
Dihydrocodeine
[- aka dihydrocodeine tartrate and DF118 Forte (trade name);
- Potency similar to codeine;
- Routes: SC or IM (controlled) or oral (not controlled)]
45
Where do opioid analgesics target?
- Spinal cord [dorsal horn pathways associated with paleo-spinothalamic pathway];
- Central regulation of pain in periaqueductal grey matter, nucleus reticular paragigantocellularis, raphe magnus nucleus;
- They produce their effects via specific receptors which are closely associated with the neuronal pathways that transmit pain to the CNS.
46
What are the problems with opioid analgesics?
- Relatively ineffective for dental pain;
- Dependence: psychological and physical;
- Tolerance: only to depressant effects;
- Dose of drug needs to be progressively increased, for same pain relief, as tolerance increases.
47
What common side effects are there of opioid analgesics?
- Effects on smooth muscle: constipation;
| - Urinary and bile retention.
48
What effects do opioid analgesics have on the CNS?
Depresses:
- Pain centre (alters awareness/ perception of pain);
- Higher centres;
- Respiratory centre;
- Cough centre;
- Vasomotor (hypotension).
Stimulates:
- Vomiting centre (dihydrocodeine often causes nausea and vomiting which limits its value in dental pain);
- Salivary centre;
- Pupillary constriction.
49
What side effects can be seen from opioid analgesics?
- 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/ pruritus.
50
What can the effects of opioids be enhanced by?
Alcohol
51
What groups should you be cautious about when prescribing opioid analgesics?
- Hypotension;
- Hypothyroidism;
- Asthma;
- Decreased respiratory reserve;
- Prostatic hyperplasia;
- Pregnancy/ breast-feeding;
- Hepatic impairment (may precipitate coma - reduce dose or avoid);
- Renal impairment (reduce dose or avoid);
- Elderly and debilitated (reduce dose);
- Children;
- Convulsive disorders;
- Dependence;
- Suspected head injury.
52
When are opioid analgesics contraindicated?
- Acute respiratory depression;
- Acute alcoholism;
- Raised inter cranial pressure/ head injury (interferes with respiration, affects pupillary responses vital for neurological assessment).
53
What is codeine derived from?
Opium poppies
54
How potent is codeine, compared to morphine?
1/12th
55
What properties can codeine offer?
- Effective orally;
- Low dependence;
- Usually in combination with NSAIDs or paracetamol e.g. co-codamol (8mg codeine, 500mg paracetamol);
- Effective cough suppressant;
- Available OTC.
56
What is a typical dose for oral dihydrocodeine?
- 30mg;
| - Every 4-6 hours, as necessary.
57
What drugs can dihydrocodeine potentially interact with (serious)?
- Antidepressants MAOIs;
| - Dopaminergics (Parkinsonism).
58
What signs and symptoms are there of an opioid overdose?
- Varying degrees of coma;
- Respiratory depression;
- Pinpoint pupils.
59
What antidote drug is indicated if there is a coma or bradypnoea (as a result of opioid overdose)?
Naloxone
[shorter duration of action than many opioids so close monitoring required and repeated injections/ infusions may be necessary according to respiratory rate and depth of coma]
60
What neuropathic or functional pain might be seen in dentistry?
Neuropathic:
- Trigeminal neuralgia;
- Post-herpetic neuralgia.
Functional:
- TMJ pain;
- Atypical facial pain.
61
What drug can dentists prescribe for neuropathic or functional pain?
Carbamazepine (Tegretol)
[anti-convulsant]
62
What other drugs are used to treat trigeminal neuralgia? (not on dental list)
- Gabapentin;
| - Phenytoin.
63
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 sensitivity.
64
What dose of carbamazepine should be prescribed for trigeminal neuralgia?
Initially:
- 100 or 200mg tablets (starting dose 100mg but some patients require higher);
- 1 or 2 times daily;
- Gradually increase according to response.
Usual dose:
- 200mg;
- 3-4 times daily;
- Up to 1.6g daily in some patients.
65
What side effects can be seen with carbamazepine?
- Dizziness;
- Ataxia;
- Drowsiness;
- Leucopenia and other blood disorders;
- SEE BNF.
[Patient blood monitoring: blood count and liver fn]
66
When is carbamazepine contraindicated?
- AV conduction abnormalities (unless paced);
- History of bone marrow depression;
- Porphyria.
67
What groups should you be cautious about when prescribing carbamazepine?
- Hepatic/ renal/ cardiac disease;
- Skin reactions;
- History of haematological reactions to other drugs;
- Glaucoma;
- Pregnancy/ breast-feeding;
- Avoid abrupt withdrawal.
