Routine monitoring unneeded for most patients on oral dermatophyte therapy

Last Updated: 2018-10-30

By Marilynn Larkin

NEW YORK (Reuters Health) - Healthy adults and children treated with oral terbinafine or griseofulvin for dermatophyte infections don't need to be monitored for liver or blood abnormalities, researchers say.

These drugs "are helpful treatments when systemic therapy is indicated for patients with fungus disorders of the skin, hair and nails," Dr. Erik Stratman of Marshfield Clinic in Wisconsin told Reuters Health by email.

"In my experience, many patients have been scared away from even considering oral terbinafine because of prescribers' fearing the liver toxic effects of the medication," he noted.

"For those who receive the oral antifungal treatments, laboratory monitoring is often performed, as this is what the drug package insert and textbooks instruct prescribers to do," he said.

But, he added, he prescribes these medications regularly and in his experience, "test after test" is either normal or minimally abnormal with no clinical impact on the patient or treatment course.

Dr. Stratman and colleagues reviewed data on 4,985 patients (mean age, 42.8; 45.9% women) who received 4,309 courses of terbinafine, 634 courses of griseofulvin microsize, and 159 courses of griseofulvin ultramicrosize from 2006 through 2016.

"We found that...laboratory abnormalities are incredibly uncommon (and) are actually more likely to occur with patients taking regular doses of acetaminophen," Dr. Stratman said.

As reported online October 17 in JAMA Dermatology, 212 (93.4%) of the abnormalities were grade 1 and did not require subsequent laboratory testing or medication discontinuance.

Elevations in alanine aminotransferase were infrequent during monitoring and were comparable to baseline detection rates in this patient population: 3.5% versus 3.6% for terbinafine; 2.1% versus 3.7% for griseofulvin microsize; and 0 versus 5.0% for griseofulvin ultramicrosize.

Rates of elevated aspartate aminotransferase, anemia, lymphopenia, and neutropenia were also infrequent and equivalent to baseline rates.

"Routine interval laboratory test result monitoring appears to be unnecessary in adults and children without underlying hepatic or hematologic conditions taking terbinafine or griseofulvin for dermatophyte infections," the authors state.

"We still plan to check baseline blood work to ensure that we are beginning treatment with a patient who does not already have an unknown underlying liver or blood count abnormality," Dr. Stratman noted. "We plan to...stop routinely checking regular monitoring bloodwork in healthy patients doing well on therapy."

Dr. Nima Majlesi, Director of Medical Toxicology at Staten Island University Hospital in New York City, commented, "This study does not differentiate subsets of patients who take the medications for more than eight weeks (and) who are most at risk for the complications they are studying."

Further, he said in an email to Reuters Health, "I do not believe this is a large enough sample size (for) evaluating the highest risk patients."

"In addition," he noted, "one major limitation of all of these studies, which the authors addressed, is the issue of compliance. The inability to confirm whether these patients were actually taking the medication as prescribed will always limit the interpretation of the results."

"But overall, I do agree with the conclusion that routine laboratory monitoring is not required for those patients taking a short course of these medications," he said. "It is well known that courses less than eight weeks do not require routine laboratory monitoring."

"I would still caution physicians to consider laboratory monitoring in those patients who will take the medication for a prolonged period of time - i.e., over 8 weeks," he added.

"Probably more useful than laboratory monitoring is patient education in terms of symptoms to be aware of while taking the medication, such as upper abdominal pain, dark urine, black stools, change in the color of skin, excessive itching, fever, rash, etc.," Dr. Majlesi concluded.

SOURCE: http://bit.ly/2OgmjhZ

JAMA Dermatol 2018.