Analgesia Flashcards
Describe the pain pathway.
Tissue injury causes injury to the phospholipid cell membrane, causes release of arachidonic acid.
COX-1 and COX-2 are produced which causes production of prostaglandin.
Prostaglandin sensitises the tissues to make them more susceptible to feeling the pain.
5-lipoxygenas pathway also activated- produces leukotrienes- causes pain and inflammation.
What is aspirin?
NSAID- has analgesia, anti-inflammatory and antipyretic effects.
What is the mechanism of action of Aspirin?
Inhibits COX-1 and COX3- so prostaglandin production is decrease.
Why are people more at risk of bleeding if they take aspirin?
COX-1 is invovled in platelet aggregation.
What are the adverse effects of aspirin?
GIT problems- prostaglandins usually inhibit acid secretion in the stomach and increase blood flow through the gastric mucosa- this would be inhibited in aspirin.
Hypersensitivity- rashes, angiooedema, acute bronchospasm
Overdose
Mucosal burns- direct effect of salicylic acid
- Aspirin must be taken with water.
What groups of people should not take aspirin?
Peptic ulceration
Epigastric pain
Bleeding abnormalities
Anti-coagulants- enhances effect of warfarin
Pregnancy/breast feeding- risk of haemorrhage, may cause Reye’s syndrome in breast feeding.
Patients on steroids- because of peptic ulcer risk
Renal/hepatic impairment
Children and adolescents under 16 years old- because of the risk of Reye’s syndrome.
Asthma
Hypersensitivity to NSAIDs
Taking other NSAIDs
Elderly
G6PD-deficiency
What is Reye’s syndrome?
Fatty degenerative process in lover and profound swelling in the brain.
Encephalopathy
Liver damage
Which of these groups is aspirin completely contraindicated in?
Children and adolescents under 16 years of age
Breastfeeding
Previous or active peptic ulceration
Haemophillia
Hypersensitivity to aspirin
What dose of aspirin should be prescribed?
300mg, 40 tablets, 2 tablets 4 times a day for 5 days after food.
If paracetamol is not working and someone with a history of peptic ulceration requires an NSAID. What would you prescribe them?
Proton pump inhibitor.
Lansoprazole- 15mg, 1 capsule ones a day for 5 days.
What is Ibuprofen?
NSAID
Less effects on platelets than aspirin but still can be irritant to the gastric mucosa.
May cause broncho-spasm.
What is the recommended drug regime for Ibuprofen?
400mg tablets, 1 tablet four times a day for 5 days.
- Taken after food.
WHat is the maximum adult dose of Ibuprofen?
2.4mg in 24 hours.
In what groups of patients should you be cautious with prescribing Ibuprofen?
Asthmatics
Gastric irritation
Peptic ulceration
Previous sensitivity to NSAIDs
Elderly
Pregnant and lactation
Renal, cardia or hepatic impairment
Patients taking other NSAIDs
Patients on long term steroids.
What are the potential side effects of Ibuprofen?
GIT discomfort- bleeding and ulceration
Hypersensitivity reactions
Headache, dizziness, drowsiness, fluid retention, renal impairment, hepatic damage.
What are some of the potential drug interactions with Ibuprofen?
ACE inhibitors
Anticoagulants
Antidepressants
Corticosteroids
Beta-blockets
Calcium-channel blockers
Lithium
Tacrolimus
What is the mode of action of paracetamol?
Inhibits the positive feedback of COX by hydroperoxides.
- thus indirectly inhibiting COX.
What are the effects of paracetamol (in general terms)?
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
In which patients should you be cautious of prescribing paracetamol to?
Hepatic impairment
Renal impairment
Alcohol dependence
What are the side effects of paracetamol?
Rashes
Blood disorders
Hypotension reported on infusion
Liver damage
What is the recommended dosage of paracetamol?
500mg tablets, 2 tablets 4 times a day for 5 days.
- leave 4 hours in between doses
What is the maximum daily dose of paracetamol for an adult?
4g in 24 hours.
Always advise patients of the maximum daily dose and remind them that they do not exceed that.
What medication must you check first before you advise someone to take paracetamol?
Co-codamol
- Has paracetamol in it.
Anadin
Lemsip
What are opioid analgesics?
Act in the spinal cord- in the dorsal horn pathways.
- central regulation of pain.
What are some of the problems with opioids?
Dependence- withdrawal of the drug can lead to psychological cravings and the patient will become physically ill.
Tolerance- to achieve the same therapeutic effects the dose of the drug needs to be progressively increased.
Constipation
Urinary and bile retention
What are the CNS effects of opioid analgesics?
Respiratory depression
Cough centre
Pain centre- alters awareness/perception of pain
What are the potential side effects of opioids?
Nausea
Vomiting
Drowsiness
Headache
Bradycardia
Hallucinations
Dependence
Tolerance
What conditions are contraindicated to prescribe opioids?
Acute respiratory depression
Acute alcoholism
Raised intracranial pressure/head injury
What opioid analgesic can dentists prescribe?
Dihydrocodeine- 30mg every 4-6 hours as necessary
