Low-Dose Ketamine May Be a Safe Opioid Alternative, Review Confirms

Marcia Frellick

July 20, 2018

Low-dose ketamine was as effective as morphine for controlling acute pain, according to a new literature review, and should be considered as an alternative to opioids for short term pain relief in emergency departments (EDs), researchers say.

Nicholas Karlow, MPHS, a medical student at the Washington University School of Medicine in St. Louis, Missouri, and colleagues, published their findings July 17 in Academic Emergency Medicine. The researchers identified and included three randomized, controlled trials, with a total of 261 patients, in their analysis. They excluded studies in which the participants had taken opioids before ketamine.

Intravenous ketamine was not inferior to intravenous morphine in terms of pain scale reduction in a patient-level data analysis (relative reduction, 0.42; 95% confidence interval,  –0.70 to 1.54.)

The trials all tested short-term efficacy (less than 60 minutes) of ketamine given as a one-dose, single-agent bolus in adults aged 18 to 65 years in the ED. The doses were similar in the trials, as were the doses of morphine.

The authors note that because of differences in the study designs, they could not perform a meta-analysis on need for rescue medications or adverse events.

The studies suggest, however, that "ketamine has lesser risk of severe adverse reactions than morphine, but a greater risk of emergence phenomenon and dizziness," the authors write.

Opioids, the paper notes, are linked with vomiting, itching, nausea, low blood pressure, respiratory depression, and hypoxia, along with the danger of misuse and addiction.

The authors do caution that ketamine is also potentially addictive and abuses have been reported.

The authors say a less-well-known side effect of ketamine use is lower urinary tract symptoms. The symptoms seem to improve after stopping use of ketamine, they write, but could be an important consideration if patients repeatedly present to the ED needing treatment for pain.

In addition, they note that prior trials and reviews have typically studied patients receiving both ketamine and opioids because ketamine is often considered an adjunct treatment to opioids. However, that confounds direct comparisons.

Last month, the first-ever guidelines were released on ketamine use for acute pain management in a variety of settings, as Medscape Medical News reported.  

The American College of Emergency Physicians released a policy statement   earlier this year that lists low-dose ketamine as an alternative to opioids.

The authors of the current analysis say they are not suggesting that ketamine should replace opioids in the ED, and they acknowledge opioids may still be the best choice in certain cases.

"However, we do believe that it is important to establish that alternatives such as ketamine are comparable to opioids so that if a clinician decides to order it instead, they can be confident that the patient obtains appropriate analgesia in a comparable time frame," they write.

The authors have disclosed no relevant financial relationships.

Acad Emerg Med. Published online July 17, 2018.  Abstract   

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