Study aims to find if IV acetaminophen can lead to lower doses of opioids after hip replacement surgery

When considering joint replacement, many patients worry about how much pain they'll experience after surgery. It's a valid concern. Pain control is important not only to avoid discomfort. It's also essential to get a handle on pain early on so patients can move around and engage in a physical therapy program.

"At Hospital for Special Surgery, we've studied pain control at length and have excellent pain management protocols for patients who have joint replacement," explains Geoffrey Westrich, MD, research director of the Adult Reconstruction and Joint Replacement Service at Hospital for Special Surgery (HSS). "We generally strive to lower patients' use of narcotic medications, known as opioids. Although these medications do a good job at controlling pain, they can have side effects such as nausea, vomiting, dizziness, drowsiness and constipation, which are not only unpleasant, but can make physical therapy more difficult."

Dr. Westrich and colleagues have launched a study to see if intravenous (IV) acetaminophen can reduce the amount of opioid pain medicine needed after hip replacement surgery. Currently, joint replacement patients generally receive opioid medication along with the pill form of acetaminophen, commonly known as Tylenol.

"We decided to undertake this study because research shows that acetaminophen in IV form reaches a higher peak concentration in the blood much faster than oral acetaminophen, and therefore crosses the blood-brain barrier much more quickly. The brain is the target organ where acetaminophen works to reduce pain," Dr. Westrich explained. "We hypothesize that the intravenous form will be better at alleviating pain after hip replacement than the oral pill form."

Dr. Westrich and colleagues aim to determine if patients in the IV acetaminophen group have sufficient pain relief to be able to substantially reduce their opioid medication intake and accompanying side effects, and if they achieve physical therapy goals more quickly. So far, patients have been very receptive to participating in the study.

All patients will receive the standard pain control protocol, with one group getting IV acetaminophen, while the other group receives the oral pill form. Since it is a randomized, double-blinded study, neither the patients nor their doctors will know which individuals are receiving intravenous vs. oral acetaminophen. Patients receiving the IV acetaminophen will also receive a placebo in pill form, and those receiving oral acetaminophen will receive a placebo IV solution.

In addition to seeing if IV acetaminophen leads to lower doses of opioid medication, researchers will be measuring sedation effects, the achievement of physical therapy milestones, and length of hospital stay in patients given intravenous vs. oral acetaminophen.

"Because of its efficacy, general safety profile and lower risk of adverse effects compared to other pain medications, intravenous acetaminophen could be an attractive component of the overall pain management plan," Dr. Westrich said. "If we find that the IV form safely reduces the need for opioid medication, it would be advantageous for hip replacement patients."