Pain Flashcards
Drugs
Paracetamol
Opioids: Weak – codeine, tramadol Strong – morphine, fentanyl, (heroin)
Co-amoxiclav
Lactulose
Paracetamol action
Still not totally clear.
At peripheral sites, may inhibit a peroxidase enzyme which is involved in the conversion of arachidonic acid to prostaglandins (1st step in this pathway involves the enzyme, cyclooxygenase). The ability of paracetamol to inhibit peroxidase can be blocked if excessive levels of peroxide build up (as is commonly seen in inflammation)
Activation of descending serotonergic pathways possibly via 5HT3 receptor activation.
Inhibits reuptake of endogenous endocannabinoids, which would increase activation of cannabinoid receptors - this may contribute to activation of descending pathways.
Paracetamol target
Unclear.
5HT3 receptors/Cannabinoid reuptake proteins/Peroxidase
Paracetamol side effects
Relatively safe drug with few common side effects.
OVERDOSE:
Liver damage and less frequently renal damage.
Nausea and vomiting early features of poisoning (settle in 24h).
Onset of right subcostal pain after 24hindicates hepatic necrosis.
Paracetamol other
Analgesic and anti-pyretic.
Does NOT possess anti-inflammatory activity.
A number of medications contain paracetamol, so care must be taken to avoid accidental overdose. Legal restrictions on sales of paracetamol have significantly reduced the number of fatalities from overdose in the UK although, regrettably, ingestion of large amounts of paracetamol remains a common method of suicide.
In 2020, paracetamol was the 14th most commonly prescribed drug in the West London area.
Probably the most commonly prescribed over the counter (OTC) medicine in the world.
Opioids action
Over-arching mechanism at a cellular level is a depressant effect on cellular activity. Multiple sites within pain pathway, where activation of the opioid receptor leads to decreased perception or increased tolerance to pain.
Anti-tussive effect due to decreased activation of afferent nerves relaying cough stimulus from airways to brain
Opioids target
Opioid receptor
Opioid side effects
Mild – nausea & vomiting (increase activity in chemoreceptor trigger zone) and constipation (opioid receptors in GIT can reduce gut motility)
OVERDOSE - respiratory depression (direct and indirect inhibition of respiratory control centre.)
Opioid other
Prescriptions for opioids in the UK have more than doubled in the last 20 years.
In 2020, several ‘weak’ opioids or weak opioid/paracetamol combinations were among the most commonly prescribed drugs in the West London area.
Co-codamol (paracetamol + codeine) = 26th
Co-dydramol (paracetamol + dihydrocodeine) = 60th
Tramadol = 69th
Co-amoxiclav action
Amoxicillin (like all penicillin like drugs) binds to bacterial penicillin binding proteins. This prevents transpeptidation (the cross linking process for bacterial cell wall synthesis)
Clavulanate is an inhibitor of beta lactamase. Beta lactamase is a bacterial enzyme that can degrade beta lactam anti-biotics and thus confer resistance to these anti-biotics.
Co-amoxiclav target
Amoxicillin = penicillin binding proteins Clavulanate = beta lactamase
Co-amoxiclav side effects
Amoxicillin is well tolerated. Most common side effects are nausea and diarrhoea.
Co-amoxiclav other
Amoxicillin is a semisynthetic antibiotic with a broad spectrum of bactericidal activity against many gram-positive and gram-negative microorganisms
Hypersensitivity to penicillins is relatively common. Usually associated with rash but can lead to anaphylactic reactions.
Co-amoxiclav is a commonly prescribed antibiotic in hospital settings.
Lactulose action
Lactulose is a non-absorbable disaccharide. It reaches the large bowel unchanged. This causes water retention via osmosis and an easier to pass stool. It can also be metabolised by colonic bacteria. The colonic metabolism of sugars has an additional laxative effect.
Lactulose target
None
