Diphenhydramine could have role as adjunctive sedative in colonoscopy for some

Last Updated: 2018-05-07

By Will Boggs MD

NEW YORK (Reuters Health) - Diphenhydramine does not reduce the need for procedural sedatives in patients on chronic opioid therapy undergoing colonoscopy, but it improves the quality of sedation, researchers report.

"We and others have found use of diphenhydramine as adjunct sedative effective in clinical practice, and our results provide proof of concept," Dr. Salman Nusrat from the University of Oklahoma Health Sciences Center and the Veterans Affairs Medical Center, in Oklahoma City, told Reuters Health by email.

Dr. Nusrat and colleagues investigated whether the addition of diphenhydramine 50 mg to conventional sedatives would reduce the dose of fentanyl and midazolam used during colonoscopy in individuals on chronic opioids in a randomized, double-blind, placebo-controlled trial of 120 patients whose daily opioid dose ranged from 5 to 385 morphine equivalents.

Neither the mean dose of fentanyl nor the mean dose of midazolam used for colonoscopy differed significantly between the diphenhydramine and placebo groups, they report in Gastrointestinal Endoscopy, online April 21.

Most patients in both groups were adequately sedated, and qualitative analysis by physicians and nurses showed no significant difference between groups.

When measured independently using a 7-point scale, however, the quality of sedation scores were significantly better with diphenhydramine than with placebo, though physicians' and nurses' scores differed by 1 point or less between the groups.

Mean patient-reported scores for pain and amnesia were significantly better in the diphenhydramine group, with differences of 1.04 for pain and 1.3 for amnesia on a scale from 1 to 10. Median patient-reported scores for pain and amnesia did not differ between the groups, however.

Adverse event rates were low in both groups, and there were no major adverse events in either group.

"Our results suggest that the use of diphenhydramine would improve the experience of this group of patients who have traditionally been difficult to sedate," the researchers conclude. "Further studies to identify the characteristics of patients with inadequate sedation and doses outside the recommended range, despite use of diphenhydramine as an adjunct, will help to better streamline the care of these patients."

"Chronic opioid therapy doesn't mandate deep sedation, and in most patients on chronic opioid therapy adequate sedation can be achieved using a combination of fentanyl, midazolam, and diphenhydramine," Dr. Nusrat said.

"Timing of diphenhydramine administration might be important," he said. "Our results support identification of patients at risk of poor sedation and administration of diphenhydramine at the start of the procedure, rather than waiting for conventional sedatives to fail."

SOURCE: https://bit.ly/2rpwg3n

Gastrointest Endosc 2018.