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Pharmacist FAQ

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Answers from
The Pharmacists
America TrustsSM

Topic: Allergy
Question: My favorite over-the-counter allergy medicine now has phenylephrine instead of pseudoephedrine. What's the difference? Will it work as well as the old formula?

Answer:Both pseudoephedrine and phenylephrine are decongestants used to treat nasal congestion due to allergies, colds, sinus infections, etc. Since pseudoephedrine can be made into methamphetamine, the U.S. Senate passed a bill restricting its sale. Products containing phenylephrine can not be made into methamphetamine, so their sale is not restricted.

Unfortunately, no studies have been done to confirm whether these two decongestants are equally effective. There are some differences in the way the drugs are absorbed by the body:

§ The intestines will absorb only about 38 percent of the amount of phenylephrine in one tablet, while pseudoephedrine is 100 percent absorbed.

§ The effects of phenylephrine do not last as long as pseudoephedrine. Therefore, phenylephrine needs to be taken every four hours, while pseudoephedrine can be taken every four to six hours.

Since people will react differently to each medication, it is difficult to say whether they are equally effective. If you are considering trying either medication, discuss it with your doctor or pharmacist first. People with certain medical conditions such as diabetes, heart disease, high blood pressure, and overactive thyroid should not take products containing either of these ingredients. Also, people taking propranolol or certain antidepressants should avoid using these products.

Learn more about drug interactions.

Visit our Allergy Center.

View Allergy products.

View the Walgreens.com Pharmacist FAQ Archives for a list of all commonly asked questions.

DISCLAIMER: The information provided is not a substitute for medical advice. Consult your physician for diagnosis and treatment of your medical condition. Advances in medicine may cause this information to become outdated, invalid or subject to debate. Professional opinions and interpretations of the scientific literature may vary. Walgreens' terms of use and general warranty disclaimer apply to all services provided. If you are in need of immediate medical attention, contact your physician, poison control center or emergency medical professional. If you need to speak with a pharmacist for non-emergency matters, contact your local Walgreens pharmacist or call a Walgreens.com pharmacist toll-free at 1-877-250-5823.