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Paracetamol: it’s all about the dose

Updated: Jun 30, 2022

Paracetamol is one of the most under-used drugs in veterinary medicine. I’m talking here specifically about analgesia for dogs in the acute setting.

But there’s no evidence, right? Wrong! We now have a good amount of evidence that provides us clear direction regarding dose. I’ve explored this evidence in a recent webinar entitled ‘Paracetamol in dogs: the evidence in black & white’.

This pain update is a quick read – for a comprehensive understanding please watch our webinar.

When discussing paracetamol, the dose clearly differs between oral and IV use – which from basic pharmacokinetics, makes sense.

Paracetamol 15 mg/kg IV has been compared to meloxicam 0.2 mg/kg IV or carprofen 4 mg/kg IV in dogs undergoing ovariohysterectomy. In this study the outcome measures were pain scores and the use of rescue analgesics. These investigators showed that paracetamol at this dose was as effective as meloxicam or carprofen for controlling pain following this surgical procedure. The dogs were studied for 48 hrs with paracetamol administered every 8 hours during the study. No adverse events were noted in this study. Although a commonly used dose IV is 10 mg/kg, we don’t have evidence to support that dose so perhaps 15 mg/kg should become the new normal?

Original work examining the anti-inflammatory effect of paracetamol showed that at approx. 25 mg/kg TID per os paracetamol was analgesic in dogs, but lacked significant anti-inflammatory effect. When 10 mg/kg PO was trialled in the same study design an analgesic effect was not demonstrated. These studies were from 1988 and 1991 so it is not clear where the commonly used 10mg/kg PO came from – it’s probably not effective in the majority of dogs. These studies were rudimentary in design and lacked a sample size calculation.

Many years later a study examining paracetamol in combination with hydrocodone showed that a dose of 13-18 mg/kg did not provide acceptable analgesia following stifle surgery.

A recent study compared oral paracetamol/codeine (Pardale-V – the licensed UK product) with meloxicam given orally prior to surgery. Paracetamol was dosed at 33mg/kg PO TID (the licensed dose) and meloxicam at 0.2mg/kg PO initially followed by 0.1 mg/kg. Both drugs were given for 3 days. Non-inferiority was demonstrated between Pardale V and meloxicam. This provides us with useful evidence regarding oral dosing and gives us options for those dogs that cannot tolerate an NSAID but are undergoing surgery. It should be noted that these dogs received methadone as premedication and buprenorphine every 8 hours post op.

For considerations when using paracetamol for chronic pain click here for our pain update.

So it is clear that when using paracetamol we need to think dose and route of administration. I hope you enjoy the webinar!

References within webinar.

This post was written by Matt Gurney. Matt & Carl established Zero Pain Philosophy to provide educational resources to veterinary professionals enabling optimal management of pain. Matt Gurney is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and works at Anderson Moores Veterinary Specialists. Matt is President of the European College of Veterinary Anaesthesia & Analgesia. Carl Bradbrook is an RCVS & European Specialist in Veterinary Anaesthesia & Analgesia and is President of the Association of Veterinary Anaesthetists. Carl works at Anderson Moores Veterinary Specialists.

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