OS- Analgesia Flashcards
When should a patient start taking analgesics?
Before the local anaesthetic wears off
What causes the formation of prostaglandins?
Trauma and infection.
What do prostaglandins do?
They sensitise the tissues to other inflammatory products causing pain.
What do hydroperoxides do?
These exert a positive feedback to stimulate COX activity (used for the production of prostaglandins)
Describe how aspirin works?
It works as an analgesic- inhibiting cyclo-oxygenases (COX-1 & COX-2) to reduce prostaglandin production.
Antipyretic- to prevent:
- the temperature raising effects of interleukin-1
- The rise in brain prostaglandin levels
- The elevated temperature in fever.
Anti-inflammatory- Reduces redness and swelling at the site of injury (by reducing vasodilation and capillary permeability)
Anti-platelet- reduces risk of another myocardial infarction.
Metabolic- It increases base metabolic rate, reducing blood sugar.
What are the side effects of aspirin?
- The reduction in prostaglandins makes patients more likely to develop ulcers and GORD.
- Asymptomatic blood loss from the GIT
- Hypersensitivity reactions
- Overdose- Hyperventillation/ Tinnitus/ Vasodilation and sweating.
- Can cause chemical burns- as it has no topical effect.
What patients should avoid aspirin and why?
Patients with peptic ulcers (as it could cause ulcer perforation)
Patients with bleeding abnormalities (it causes GI bleeding)
Children under 16 (It can cause Reye’s syndrome)
Patients with hypersensitivity to aspirin or other NSAIDS
History of epigastric pain
Those being treated with anticoagulants- (aspirin interacts)
Pregnancy (aspirin may cause impaired platelet function affecting baby)
Patients on steroids (25% of patients on steroids develop a peptic ulcer
Renal/ hepatic impairement (metabolism & excretion problems)
Patients taking other NSAIDs ( combination of NSAIDs increases side effects)
Elderly (are more suceptible to drug induced side effects as they are smaller)
G6PD deficiency- patient is predisposed to blood cells breaking down .
What is reye’s syndrome
Where there is a fatty degenerative process in the liver and swelling in the brain.
It has a 50% mortality rate.
How does aspirin interact with warfarin?
Through displacing warfarin from the binding sites.
This causes an increase in free warfarin which increases the tendency to bleed.
What is the dosage used for prescribing patients with aspirin.
40 x300mg tablets
2 tablets
4 times a day after food
For 5 days
Maximum daily dose- 4g
How does a patient with peptic ulcer disease affect your aspirin prescription?
A protein pump inhibitor should be prescribed for protection
e.g.
5x15mg lansoprazole capsules
1 capsule
once a day.
How does ibruprofen work?
It has a similar effect to aspirin however with a lower risk of gastric mucosa irritation
Discuss the side effects of ibruprofen.
GIT- discomfort/occasional bleeding/ ulceration
hypersensitivity reactions
Overdose.
What patients should avoid ibuprofen?
- Previous or active peptic ulceration
- Elderly
- Pregnancy and lactation
- Renal/cardiac/ hepatic impairement
- History of hypersensitivity to aspirin and other NSAIDs
- Asthma
- Patients taking other NSAIDs
- Patients on long term systemic steroids.
What is the adult dose presrcibed for ibruprofen
20x400mg tablets
1 tablet
4 times a day
5 days
Maximum daily dose 2.4g
How does paracetamol work?
It blocks the positive feedback of hydroperoxide causing inhibition of COX- reducing prostaglandin production in the pain pathways.
This causes- analgesia/ antipyretic.
It is not anti-inflammatory.
Discuss the side effects of paracetamol
Rashes
Blood disorders
Hypotension on infusion
Overdose- damages the liver
10-15g (20-30 tablets taken within 24 hours can cause overdose)
What patients should not be prescribed paracetamol?
Patients with:
Hepatic impairment
Renal impairment
Alcohol dependance.
What drugs interact with paracetamol?
Cytotoxics
Domperidone (anti-sickness drug used to treat nausea)
Metocloparmide
Lipid regulating drugs.
What is the adult dose for paracetamol?
40x 500mg tablets
2 tablets
4 times daily (i.e. 8 tablets)
For 5 days
Max dail dose 4g.
Discuss the problems with prescribing opiods.
The patient can become dependent on the opioid.
The patient will become tolerant to the drug. (progressively needs more to achieve the same effect)
How do opioids work?
These act in the spinal chord (relatively ineffective in dental pain)
Depressing the:
- Pain centre
- Higher centres
- respiratory centres
- Cough centre
- Vasomotor
Stimulating :
- Vomiting centre
- Salivary centre
- Pupilary constriction
What are the side effects of opioids?
Nausea and vomiting.
Drowsiness
Larger doses produce respiratory depression and hypotension.
Constipation/urinary and bile retention.
Overdose-can cause a coma.
What patients should you avoid prescribing opioids to?
Those with:
- Acute respiratory depression
- Acute alcoholism
- Raised intercranial pressure/head injury- opiods interfere with respiration and affect pupillary responses that are vital for neurological assessment.
What drugs interact with opiods?
Interacts with:
Alcohol
Antidepressants (MAOIs)
Dopaminergics (parkinsonism)
What opiod do we prescribe in dentistry and what is the dose?
Dihydrocodeine
30mg every 4-6 hours
(As necessary)
How do we treat neuropathic and functional pain?
Carbamazepine
How does carbamazepine work?
It is a sodium channel blocker which prevents the firing of an action pottential.
What are the side effects of cabamazepine?
Dizziness
Ataxia- disease with behaviour similar to being drunk
Drownsiness
Leucopenia and other blood disorders.
What patients should carbamazepine be avoided in?
AV conduction abnormalities (unless the patient has a pacemaker)
Patients with a history of bone marrow depression
Porphyria.
What dose of Carbamazepine shoudl be used to treat trigeminal neuralgia?
100mg once or twice daily to begin with.
Increase dose according to response
(200mg tablet 3-4 times daily- 1.6g daily max)
