Allergy medications like antihistamines can provide relief during autumn, but a new study suggests they may be lethal to victims of the opioid epidemic.
Researchers at the Centers for Disease Control and Prevention identified approximately 92,000 drug overdose deaths in 43 states and D.C. between 2019 and 2020, and found at least 18% involved or tested positive for antihistamines.
More than 71% of those deaths included diphenhydramine, commonly known by its brand name Benadryl, according to the study published last week in the agency’s Morbidity and Mortality Weekly Report.
Only 90 deaths – fewer than .1% – involved antihistamines as the sole drug, while more than 82% of the deaths co-involved opioids.
“It’s a good wake up call for us to continue checking what other potential drug combinations happen in overdoses” and to monitor more closely, said Dr. Silvia Martins, professor of epidemiology and director of the Substance Use Epidemiology Unit at Columbia University Mailman School of Public Health, who is unaffiliated with the study.
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Sedating antihistamines, like diphenhydramine, can exacerbate opioid-induced respiratory depression, which is characterized by decreased breathing and the most common cause of death during an overdose, Martins said.
Naloxone can typically reverse the effects of an opioid overdose, including opioid-induced respiratory depression, but it has no effect on antihistamines.
“Because antihistamines do not respond to naloxone, co-involved opioid and antihistamine overdoses might require naloxone administration plus other immediate medical response measures to prevent death,” said lead author Amanda T. Dinwiddie, a health scientist at the National Center for Injury Prevention and Control’s division of overdose prevention.
The study doesn’t capture why people took antihistamines with opioids, but Martins said there are reasons that go beyond enhancing the opioids’ effects.
Some may have taken antihistamines to alleviate side effects related to long-term opioid use, she said, like itching, nausea and disordered sleeping. Others may have taken the medication to treat their allergies.
“Some might have tried to self-medicate side effects (with antihistamines) and inadvertently got more sedated,” Martins said.
The illicit drug supply may have also been tainted by antihistamines without the user’s knowledge, Dinwiddie said .
Although it’s unclear how they were consumed, health experts say it’s important for users to be aware of the dangers associated with taking antihistamines and for providers to be mindful when treating opioid overdoses.
“We need to have educational campaigns at the practitioner level and the general population level so people understand the risk of combining different substances,” Martins said.
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
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