Recent research by a University professor shows that taking simple antihistamine drugs such as Allegra and Zantac can limit the sudden drop in blood pressure that causes some people to faint or become nauseous after exercise.
Human Physiology Professor John Halliwill’s research showed a link between the activation of histamine receptors in the body and the lower blood pressure that is known to occur during post-exercise recovery.
“For a long time we’ve been trying to understand what happens with the cardiovascular system as we recover from a bout of exercise,” Halliwill said.
Halliwill said initial experiments gave subjects Allegra and Zantac individually and measured their bodies’ responses. He said the Allegra had a stronger immediate effect, reducing the drop in blood pressure as soon as 30 minutes after the exercise. The Zantac had a more long term effect, Halliwill said, having the same effect over an hour after subjects began the recovery period.
Allegra is a common allergy medicine available by prescription. Zantac is an acid reflux medication available over the counter.
For the most recent study, Halliwill said, subjects received both drugs at the same time before they exercised. Here the results were more dramatic.
“We found out that we could completely wipe out the blood flow or blood pressure response during recovery from exercise,” Halliwill said, noting that these subjects experienced no drop at all in blood pressure.
Halliwill said the decrease in blood pressure after exercise can actually be good for some. While it may cause fainting or nausea in people with normal blood pressure levels, he said, it can also bring someone with extremely high blood pressure to begin with down to a normal level.
“Blood pressure change is kind of a two-edged sword,” Halliwill said.
Gary Klug, head of the human physiology department, said Halliwill’s studies are important to the department’s focus on research with practical application.
“Everyone in our department is working on that interface between basic science and clinical medicine,” Klug said. “I think John’s research definitely does that.”
For the initial exercise portion of the study, Halliwill asked 28 subjects to ride a stationary bike for one hour at a moderate pace.
“It’s hard enough that you know you’re exercising, but it’s not so hard you can’t carry on a conversation,” he said.
Halliwill and his researchers monitored subjects’ blood pressure, heart rate and blood flow during the exercise and during a 90-minute recovery period while they lay on a bed.
The experiment also used two separate groups of different athletic ability, Halliwill said. One was composed of well-trained runners and cyclists, and the other was made up of more modest athletes who said they exercise less than 30 minutes per week.
Halliwill said the drop in blood pressure was very similar between the two groups, but the decrease was more substantial in people with dangerously high blood pressure, or hypertension.
Jennifer McCord, a human physiology graduate student who assisted in the study, said the research still has potential to lead to a lot more.
“Now that we’ve been able to block the decrease in blood pressure, we’re going in a clinical direction,” she said.
McCord said the study could help prevent people from passing out after exercise or help people who may benefit from a drop in blood pressure.
“We’re also still looking at the anti-hypertension aspect,” McCord said.
Halliwill said there is more work to be done with the body’s basic response to exercise without the use of antihistamines.
“When we see something physiologically that is activated in every single person that we study again and again, it suggests to us that maybe it’s serving some purpose,” he said. “There may be some benefit to that response.”
The benefits of decreasing blood pressure and blood flow directed to working muscles, Halliwill said, may include developing blood vessels and adapting to exercise more intensely and for longer periods of time.
He also said antihistamines could have greater practical use by limiting changes in blood pressure.
“That’s one of the topics we’re currently exploring,” Halliwill said.
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