Paracetamol Flashcards
What are indications for paracetamol use?
- First-line analgesia
- Antipyretic
What is the mechanism of action of paracetamol?
Has at least two separate mechanisms of action, one on the COX pathway, and one on the cannabinoid system.
- COX pathway - thought to be a selective COX-2 inhibitor, meaning that in theory it does not block production of protective prostaglandins associated with COX-1, but does block the prostaglandins that are associated with COX-2 and ultimately the production of pain.
- Cannabinoid system - Paracetamol is metabolised to AM404 which has several effects; prevention of the neuronal uptake of a cannabinoid produced naturally, called anandamide, a compound which activates nociceptors and leads to the perception of pain.
How can paracetamol be given?
- Orally
- IV
- PR
What is the most serious complication of using paracetamol?
- Paracetamol toxicity
- Hepatotoxicity
How is paracetamol toxic to the liver?
Paracetamol is metabolised by cytochrome P450 enzymes to a toxic metabolite (N-acetyl-p-benzoquinone imine [NAPQI]), which is conjugated with glutathione before elimination. After overdose, this elimination pathway is saturated, and NAPQI accumulation causes hepatocellular necrosis
What are side effects of paracetamol?
Liver failure
When should you take caution with paracetamol use?
- Chronic alcohol use
- Malnutrition
- Low BMI
- Severe hepatic impairment
What is the usual dose of paracetamol in adults?
0.5-1g every 4-6 hours
What do you need to determine before administering paracetamol?
Patients weight
What weight would you consider reducing the dose of paracetamol?
<50kg
What dose of paracetamol would you prescribe if someone weighed less than 50kgs?
15mg/kg every 4-6 hours
How would you administer IV paracetamol?
Pre-prepared as a solution that can be infused undiluted over 15 minutes or diluted in 0.9% sodium chloride or 5% glucose solution before administration
