THE FDA approved the use of I.V. acetaminophen in November 2010, but it has been commercially available in many countries outside the US since 2001.1 I.V. acetaminophen is indicated for managing mild-to-moderate pain, moderate-to-severe pain along with adjunctive opioid analgesics, and fever in adults and children as young as 2 years.2 This article examines the evidence supporting the use of acetaminophen and reviews important nursing considerations.

Research findings

In 2015, a meta-analysis of 11 clinical trials evaluating 740 patients showed that I.V. acetaminophen is an effective intervention to reduce post-op pain when used as a single-dose preventive regimen and helps reduce post-op nausea and/or vomiting, when compared with a placebo or no medication.3

Shaffer and colleagues conducted a retrospective cohort study that included 2,238,433 inpatient encounters across 297 hospitals, with 271,394 encounters involving I.V. acetaminophen.4 This investigation indicated that including I.V. acetaminophen in the plan for post-op pain management has the potential to decrease length of stay, opioid-related complications, and overall hospital costs.4

Nonaka and colleagues conducted a randomized controlled trial of 40 women who underwent partial mastectomies. The purpose was to compare the analgesic effect of I.V. acetaminophen to I.V. flurbiprofen, a nonsteroidal anti-inflammatory drug (NSAID).5 No significant difference in satisfaction ratings was found between the two groups of women. Because NSAIDs may increase renal, cardiovascular, and gastrointestinal adverse reactions and analgesic effects are comparable, the authors concluded that I.V. acetaminophen may be a better option than an NSAID.5

A recent clinical trial compared the antipyretic efficacy, safety, and tolerability of oral dexibuprofen (an NSAID) with I.V. acetaminophen in children between ages 6 months and 14 years admitted to the hospital for upper respiratory tract infection (URTI) with fever.6 This study's results also suggested that acetaminophen injection may be a safe and effective alternative to oral NSAIDs for pediatric patients with URTI who cannot take oral medications or who need faster fever control.6

Administration guidelines

I.V. acetaminophen is administered via infusion over 15 minutes.7 The initial dose may be repeated at intervals of at least 4 hours up to the recommended maximum dosage specified in the product labeling according to patient weight and/or age. Carefully review the warnings and precautions and do not exceed the maximum recommended daily dose for any patient. Administration of acetaminophen in doses higher than recommended may result in severe hepatic injury and death. I.V. acetaminophen has a boxed warning about the risk of medication dosing errors and hepatotoxicity.7

I.V. acetaminophen is contraindicated in patients with severe hepatic impairment or severe active liver disease. It is also contraindicated in patients with known hypersensitivity to acetaminophen or to any of the excipients in the I.V. formulation.7 It should be used with caution in patients with severe renal impairment (creatinine clearance <=30 mL/min), alcoholism, chronic malnutrition, or severe hypovolemia.7 The prescriber should consider longer dosing intervals and reduced daily doses.1 Consult the product labeling for details about potential drug interactions.

The most common adverse reactions in patients treated with I.V. acetaminophen include nausea, vomiting, headache, and insomnia in adult patients, and nausea, vomiting, constipation, and pruritus in pediatric patients.7

Advantages of I.V. acetaminophen

Because the I.V. formulation of acetaminophen is significantly more expensive than the oral formulation, many hospitals have adopted strict guidelines around when to use the I.V. form.8 However, compared with oral acetaminophen, I.V. acetaminophen can provide analgesic or antipyretic effects for children and adults who are vomiting, have intractable diarrhea, or experience other complications that prevent oral or rectal administration of acetaminophen. In addition, the drug takes effect faster when given I.V. than when administered orally or rectally.9 No dose adjustment is needed when converting between oral and I.V. acetaminophen in adults and adolescents who weigh 50 kg or more.

For some patients, I.V. acetaminophen may be safer than I.V. NSAIDs. For example, acetaminophen injection interferes less with platelet function than NSAIDs and may be safer to use in patients at risk for hemorrhage.6

I.V. acetaminophen also has advantages over opioid drugs because it does not cause some of the adverse reactions associated with opioids such as urinary retention, sedation, and respiratory depression, and it has less potential for abuse.3,9,10 Death related to misuse of prescription opioids is one of the nation's most serious public health problems.11

Summary

A review of the current evidence suggests that I.V. acetaminophen is useful when patients who have fever or pain cannot tolerate oral medication or when fever needs to be quickly alleviated. Although acetaminophen injection is more expensive than oral or rectal forms of the drug, it may decrease the need for opioid analgesics, avoiding opioid-related adverse reactions and thus decreasing overall costs related to post-op pain management.

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