UF Researcher: Don’t Be Quick To Pick Cough Syrup Just Because It’s Thick

February 13, 1997

GAINESVILLE, Fla.—Commercials and advertisements aside, thick may not be better than thin when it comes to cough syrup, University of Florida researchers say.

“It’s the drug and the dose that make the difference — not the thickness of the cough syrup,” says Don Bolser, assistant professor of physiological sciences at UF’s College of Veterinary Medicine.

Most cough preparations have two components that help reduce coughing: syrup and active drug ingredients, says Bolser, who studies the cough reflex. Despite marketing studies that show most people believe the better cough preparation is the one with the thicker syrup, the truth is syrup components of all cough preparations are virtually equally effective.

“There are rows and rows of these preparations now available for purchase over-the-counter,” Bolser says. “The marketing folks promoting these products tend to focus on things people can see, things with little or no relevance to the product’s effectiveness.”

“Coughing is a common health problem and its cause is often difficult to diagnose,” says Dr. Sidney Breyman, professor of medicine at Brown University and pulmonary division director at Rhode Island Hospital in Providence.

“Sinusitis is the most common culprit, but asthma, chronic bronchitis and the common cold also are factors.”

When faced with a persistent cough, most people turn to over-the-counter preparations for relief. If a cough persists more than a few days, however, a physician should be consulted.

“Now we are focusing our research on both over-the-counter and prescription drugs — what they do and how they act,” Bolser says. “By learning more about how these drugs act to inhibit cough, we hope to design newer, more effective drugs relatively free of side effects.”

Many consumers have misconceptions about cough preparations. The next time you’re at the drugstore mulling product labels, here are a few things you should know:

  • Drugs that inhibit cough are classified into two groups: those that act in the lungs and airways, known as peripheral drugs, and those that act in the brain, known as central drugs. Central drugs, such as codeine, often are more effective but are associated with side effects such as drowsiness and constipation. Codeine also can be addictive.
  • Not all antihistamines inhibit coughing, though they may help alleviate other cold symptoms. If the drug’s name ends in ‘amine’, it probably contains an antihistamine.
  • Have realistic expectations of expectorants. Just because a medicine contains an expectorant — to promote the coughing up of secretions — don’t expect it to make your cough go away. An expectorant commonly found in cough suppressants is guaiphenesin.
  • If you want a cough suppressant that doesn’t make you sleepy, look for preparations containing only dextromethorphan. The dose of this drug should be 15 milligrams or higher to ensure cough