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IV paracetamol provides similar level of analgesia to NSAIDs and opiates for acute pain in ED

IV paracetamol provides similar analgesic relief to other treatments used for acute pain in emergency care, but might not be the best first-line drug, a new study has found.

Use of intravenous (IV) paracetamol for patients presenting at an emergency department (ED) with acute pain, irrespective of the aetiology, provides a similar level of analgesia after 30 minutes as both IV NSAIDs or opiates. However, NSAIDs require less rescue analgesia than paracetamol, suggesting that in the absence of contra-indications, the former would be a better first-line choice. This is according to the findings of a meta-analysis by Qatarian researchers.

Pain is a common presenting complaint within an ED. For instance, a review of 1,665 visits to ED found that in 61.2% of cases, pain was documented somewhere on the chart. IV paracetamol is a commonly used analgesic, with some, albeit limited evidence of efficacy according to a review of 14 studies. Nevertheless, many of the studies included in the review had several methodological flaws, hence lowering the certainty of the findings.

Given these flaws, the researchers undertook the current study to update the earlier review, particularly as over 20 studies had been published since the original review in 2016. The team examined the comparative analgesia provided by IV paracetamol, NSAIDs (intravenous or intramuscular) or IV opioids all used alone, in adults attending an ED with acute pain due to various causes.

The primary outcome was the mean difference (MD) in pain reduction for each group (i.e. IV paracetamol, NSAIDs or opiates), 30 minutes (T30) post-dose. Secondary outcomes were the MD in pain reduction after 60 (T60), 90 (T90) and 120 (T120) minutes. The team also considered the need for rescue medication at the different time points for the three treatment interventions.

Analgesic effect of IV paracetamol

The review identified 27 trials with 5,427 patients and of which, 25 trials had data for use in the meta-analysis.

There was no significant difference in the mean pain reduction at T30 between IV paracetamol and opiates (MD = −0.13, 95% CI −1.49 to 1.22). Similarly, the difference between paracetamol and NSAIDs was also non-significant (MD = −0.27, 95% CI −1.0 to 1.54). However, while there were no important analgesic differences between the treatments, the researchers did identify significant heterogeneity across trials for all comparisons (p < 0.001 in all cases).

Despite the similar analgesic effects, the need for rescue analgesia at T30 was higher in the paracetamol compared to NSAID group (risk ratio, RR = 1.50, 95% CI 1.23 – 1.83) but not for paracetamol and opiates (RR = 1.07, 95% CI 0.67 – 1.70). Furthermore, adverse effects were 50% lower with paracetamol in comparison to opiates (RR = 0.50, 95% CI 0.40 – 0.62) but not different compared to NSAIDs (RR = 1.30, 95% CI 0.78 – 2.15).

At T60, T90 and T120, there was no difference between paracetamol and opiates though paracetamol was inferior to NSAIDs at T60.

These findings led the authors to conclude that while reductions in pain from IV paracetamol after 30 minutes were similar to the other two drug classes, since NSAID use was associated with a lower need for rescue analgesia, these drugs should be considered as a first-line treatment option unless there are contra-indications.