Maryland Researchers Find Anti-Fever Drugs May Prolong Flu

In a series of vaccine studies conducted between 1978 and 1987 at the University's Center for Vaccine Development, 54 volunteers were injected with Influenza A, 45 with S. sonnei, and 21 with R. rickettsii. During these studies, some of the subjects were given aspirin or acetaminophen for relief of symptoms such as fever. The current study compared the duration of illness in those who received the medication with those who did not.

"The analysis suggests that anti-fever therapy prolonged illness in subjects infected with Influenza A, but not shigellosis or Rocky Mountain spotted fever," says Philip A. Mackowiak, MD, one of the study's principal investigators and chief of the Medical Care Clinical Center, V.A. Maryland Health Care System and professor at the School of Medicine.

"Our research suggests that fever may have different roles in the resolution of bacterial and viral infections," says Karen I. Plaisance, PharmD, associate professor at the School of Pharmacy, the study's other lead investigator.

"The original studies weren't designed to look at anti-fever drugs," says Mackowiak. "They were designed to study the potency of several experimental vaccines. We examined the study after the fact to determine to impact of anti-fever drugs on the outcomes of infections."

Study results indicate that participants infected with Influenza A- and S. sonnei had the illness of a longer duration, but also higher maximum temperatures during this illness, and more symptoms of infection on the day of the maximum temperature.

"These findings suggest that anti-fever drugs might have been associated with prolonged illness simply because aspirin and acetaminophen were given to the sickest subjects. But an analysis of the relationship between the duration of the illness and the antipyretic therapy was considered along with several other clinical and demographic variables, and only those who were administered the drugs exhibited a statistically significant relationship with the duration of the illness in influenza A and S. sonnei-infected patients," says Mackowiak.

According to Mackowiak, further analysis suggested that anti-fever drugs caused influenza A to be prolonged but were more likely the result of prolonged illness in subjects injected with S. sonnei; in the former instance they were administered early in the course of the illness, and in the latter, late in the course of the illness.

In short, says Mackowiak, "the good news is that anti-fever drugs make people feel better when they have infections. The bad news is that they may cause the illness to linger longer. It doesn't mean people shouldn't take anti-fever drugs. It means that they should be aware that anti-fever drugs have a modest cost associated with relief and that cost is that they may be sick longer."