November 28, 2021

Antihistamine improves quality of sedation during colonoscopy

ORLANDO – The use of diphenhydramine (Benadryl) in addition to conventional sedatives decreased pain and improved the quality of sedation during colonoscopy, a researcher reported here.

The results of a randomized, double-blind study involving more than 100 patients indicated that, compared to placebo, the addition of diphenhydramine significantly improved the mean sedation scores assessed separately by physicians (mean of 6.2 vs. 5 , 3 on a scale of 1 to 7; P= 0.0002) and nurses (5.6 vs. 5.1; P= 0.04), reported Salman Nusrat, MD, of the Oklahoma Health Sciences Center in Oklahoma City.

  • Note that this study was published in summary form and presented at a conference. These data and conclusions should be considered preliminary until their publication in a peer-reviewed journal.

Diphenhydramine also appeared to improve patient comfort without increasing the number of adverse events, he said during his presentation on Monday afternoon at the World Congress of Gastroenterology at ACG2017.

Nusrat explained that as opioid use becomes more prevalent in the general population with the associated development of tolerance, patients may be less sensitive to conventional opioid sedatives, making sedation a challenge. “Patient tolerance is important to the success and safety of colonoscopy and results in increased compliance and a willingness to undergo a new procedure,” he said.

“Our results showed that although the use of diphenhydramine did not decrease the dose of conventional sedative used, it improved the quality of sedation as rated by the patient, nurses and physicians,” said declared Nusrat.

Nusrat and colleagues randomized 119 patients to Oklahoma City Veterans’ Medical Center from July 2014 to November 2016. All patients used chronic opioids (defined as at least 5 mg of morphine or its equivalent for at least 3 days per week for more than 3 months) and had to undergo a colonoscopy. Those who were pregnant, had a history of colon resection or severe cardiopulmonary disease were excluded.

In addition to receiving intravenous fentanyl and midazolam before the procedure, patients were given a 1: 1 ratio to receive either 50 mg of diphenhydramine or a placebo.

The quality of sedation was then assessed both categorically (inadequate, adequate, over-sedated) and quantitatively on a seven-point scale (from no effect to optimal sedation) separately by a physician and a nurse. Patients rated their pain on 10-point scales (1 = no pain; 10 = severe pain) and amnesia (1 = full memory; 10 = no memory) the next day.

The researchers found that diphenhydramine improved patient scores for pain (mean of 2.05 with diphenhydramine versus 3.09 for placebo) and amnesia (7.8 versus 6.5, respectively; P= 0.047 for both comparisons), although categorical assessment showed no significant difference between groups.

Hypotension episodes were more common in patients in the placebo group. There was no statistical difference in induction time, procedure duration, or recovery time between the diphenhydramine and placebo groups.

One of the main limitations of the study was that the majority of patients were over the age of 55 and were Caucasian males. Additionally, the analysis was limited to patients who were taking chronic opioids and undergoing outpatient colonoscopies.

Nusrat called for further studies to identify the optimal use of diphenhydramine as an adjunct to standard sedation.

Last updated on October 17, 2017


The researchers did not report any financial disclosures of interest.

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