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Intravenous Versus Oral Acetaminophen for Pain Control in Neurocritical Care Patients
Intravenous Versus Oral Acetaminophen for Pain Control in Neurocritical Care Patients
Nichols DC, Nadpara PA, Taylor PD, Brophy GM. Neurocrit Care. 2016;25:400-6.
Study Question: How does intravenous (IV) compare to oral (PO) acetaminophen (APAP) in analgesic effect in neurocritical care patients?
Study Description: This single-center, retrospective study evaluated patients admitted to the neuroscience intensive care unit (NSICU) who received ≥ 1 dose of IV APAP between May 2012 and April 2013. Pain assessments were based on severity of pain, meaning a more frequent and detailed assessment would be used for pain scores ≥4. Thus, IV and PO APAP doses administered with a predose pain score ≥ 4 within 1 hour of dosing were compared in this study. Pain intensity difference (PID) was calculated as the change between pain score prior to the dose administered and the score at 30 min, 1, 2, 3, and 6 hours after dose administration. Pre- and post-dose morphine milligram equivalents (MME) were calculated within 6 hours of the APAP dose. All IV APAP doses were 1 g, whereas 94% of PO APAP were 650 mg and 6% were 325 mg.
Results: A total of 309 patients received 459 doses of IV and 440 doses of PO APAP. The median PID at 30 min post-dose was significantly higher among those receiving IV APAP compared to those receiving PO APAP (4 [IQR 3-5] vs. 1 [IQR 0-4]; p = 0.003). No significant difference in PID was seen at 1, 2, 3, or 6 hours. There was also no difference in MME between the two groups at 6 hours pre- or post-APAP dose (p = 0.456 and 0.684, respectively).
Conclusion(s): IV APAP was more effective than PO APAP at improving pain scores within 30 minutes of dosing, but no differences were seen at further time points. IV APAP also did not appear to reduce opiate requirements, compared to PO APAP.
Perspective: IV APAP has been studied in various ICU patient populations for the main attractive properties of being able to decrease opioid usage for pain relief. IV APAP is seen as a useful agent for multimodal analgesia when patients are NPO. The effectiveness in achieving rapid relief of pain with IV APAP can be largely attributed to the pharmacokinetic properties of the drug and its shorter time to achieve maximum concentration. Being intravenous, there is also better systemic absorption achieved compared with the PO formulation. Although this study shows the benefit of IV APAP achieving a significant difference in PID at 30 min, at 1, 2, 3, and even 6 hours after administration, there was no significant difference in outcomes. Given the high cost of this medication relative to PO APAP, caution should be used for this indication in patients who are not NPO. Further studies are needed to assess the benefit of this rapid onset of action and its potential long-term effects for neurocritical care patients.