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Fibromyalgia, IBS patients linked to multiple-drug intolerance

UTSW study findings may help physicians diagnose patients who would benefit from drug allergy evaluations

Senior woman taking prescription
(Photo credit: Getty Images)

DALLAS – May 20, 2024 – Patients with fibromyalgia and irritable bowel syndrome (IBS) who take multiple medications are more likely to develop severe drug intolerance than healthy patients, UT Southwestern Medical Center researchers reported. Their findings, published in The Journal of Allergy and Clinical Immunology: In Practice, could help health professionals prescribe drugs for patients and identify treatment plans for multiple drug intolerance syndrome (MDIS). 

“Fibromyalgia and IBS patients are often prescribed a variety of medications, and it’s reasonable to expect that they may have more medication-related difficulties. Our study found that these patients have a higher risk of developing MDIS,” said David Khan, M.D., Professor of Internal Medicine and Pediatrics and a member of the Division of Allergy and Immunology at UT Southwestern.

David Khan, M.D.
David Khan, M.D., is Professor of Internal Medicine and Pediatrics and a member of the Division of Allergy and Immunology at UT Southwestern.

According to the researchers, MDIS affects about 2% to 6% of the U.S. population and is more prevalent among older women. Patients with MDIS often experience multiple health issues, including anxiety, depression, and a reduced quality of life.

Diagnosing MDIS requires identifying the number of medications that patients have adverse reactions to and determining the type of reactions, including intolerance and allergies. Drug intolerance reactions, such as headaches, nausea, or diarrhea, are often misidentified and mislabeled in medical records as drug allergies induced by immune system overreactions.

UTSW researchers categorized the medications and reactions to understand the severity of patients’ intolerance to treatments. They searched medical records from August 2019 to July 2020 for UT Southwestern patients diagnosed with fibromyalgia and IBS, then classified the records according to the types of drugs used. If patients reported adverse effects of three or more types of drugs, they were categorized as having MDIS or severe MDIS.

If a patient had multiple adverse reactions to the same medication, researchers counted each as a distinct occurrence. Using this labeling method, researchers identified patients with severe MDIS as those who had adverse reactions to 10 or more medications.

After analyzing 16,789 record entries, researchers used statistical methods to determine whether MDIS is more prevalent in fibromyalgia and IBS than in healthy patients with similar demographics. They found that patients with fibromyalgia and IBS were 12 and 3 times more likely, respectively, to develop severe MDIS than patients of the same ages and genders without the disorders.

The study confirmed that polypharmacy, or taking multiple medications, increased the chances of developing MDIS. This may result from prolonged exposure to a single drug or the prescribing of several less effective drugs to manage side effects.

Opiates caused the highest reported drug intolerance in fibromyalgia and IBS patients, a finding that differs from other MDIS studies in which antibiotics or anti-inflammatory medications often have been the most common, Dr. Khan said.

This study highlights the need for effective delabeling strategies for patients with multiple comorbidities and ensuring adequate treatment options for MDIS.

“Patients diagnosed with fibromyalgia and IBS, particularly those with multiple drug allergy labels listed in their medical records, might benefit from evaluations assessed by an allergy specialist to tailor effective treatment,” Dr. Khan said.

According to Dr. Khan, this study was conceived and carried out independently by first author Alicia Alvarez, M.D., a former fellow in the UTSW Division of Allergy and Immunology, with guidance and mentorship from Dr. Khan and Jayme Palka, Ph.D., Assistant Professor of Psychiatry.

Dr. Khan is also the Director of UTSW’s Allergy and Immunology Fellowship program and Director of the Allergy and Asthma Clinic at Parkland Health.

About UT Southwestern Medical Center 

UT Southwestern, one of the nation’s premier academic medical centers, integrates pioneering biomedical research with exceptional clinical care and education. The institution’s faculty members have received six Nobel Prizes and include 25 members of the National Academy of Sciences, 21 members of the National Academy of Medicine, and 13 Howard Hughes Medical Institute Investigators. The full-time faculty of more than 3,100 is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide care in more than 80 specialties to more than 120,000 hospitalized patients, more than 360,000 emergency room cases, and oversee nearly 5 million outpatient visits a year.