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Cough medicine creates dangerous interaction

Cough medicine creates dangerous interaction


Joe Graedon and Dr. Teresa Graedon

Question: I experienced serotonin syndrome once, even though I used a drug interaction checker. Unfortunately, it was hard to use. As a result, I had a scary experience.

Being a wary person, I went to an online interaction checker and typed in “Prozac.” When it told me that it found no drug interactions, I typed in “fluoxetine.” Again, nothing.

So, I, a Prozac patient, went ahead and took my cough medicine. Before long, I was frazzled, agitated, trembling and saying things that made no sense. Luckily, this subsided after a few hours.

Suspecting an interaction, I went back to that interaction checker and typed in “fluoxetine dextromethorphan.” Presto! I saw that this combination could have sent me to the hospital. Why isn’t this better known?

Answer: Many antidepressants, including fluoxetine (Prozac), paroxetine (Paxil) and sertraline (Zoloft), can interact with cold medicines containing the cough suppressant dextromethorphan (DM) or the antihistamine chlorpheniramine (British Journal of Clinical Pharmacology, December 2010). This potential interaction is not widely recognized.

The resultant serotonin syndrome can be life-threatening. Symptoms may include confusion, agitation, diarrhea, nausea or vomiting, rapid heart rate, muscle spasms, fever, overactive reflexes, hallucinations and rapid changes in blood pressure.

Investigators found that nearly 8% of the patients in an intensive care unit met criteria for serotonin syndrome, though none of them had been diagnosed (Journal of Critical Care, June 2021). Most of these patients had taken at least two serotonergic drugs, including ondansetron (Zofran), tramadol (Ultram), dextromethorphan or chlorpheniramine.


Question: My Medicare Advantage Plan is always trying to get me to have my medicines mailed because it is cheaper. Instead, though, I get my prescriptions filled locally, where I know my pharmacist.

One time, a doctor prescribed me a new drug. Since I was in a hurry, I stopped at the nearest pharmacy. However, when they quoted the price, I said, “Oh no!”

I drove a few blocks further and went to my usual pharmacist. When he looked at the prescription, he told me my insurance would not cover it. However, they would cover an alternative, and he named it. Then he advised me to call the doctor to see if that would work as a substitute.

I did, and she prescribed it. I am still using this medicine, which is working well. That’s the reason I refuse to buy my medicines through the mail. The slight extra cost is well worth it.

Answer: Having a vigilant pharmacist who is watching out for potential drug interactions as well as what your insurance will and won’t cover is invaluable. Finding an affordable alternate medication can sometimes be challenging.

If there is no substitute, there are a couple of options. Consumer Reports mentions that Costco has good prices at their pharmacies, which you can use without becoming a member. They also suggest checking to learn the drug’s fair price. Coupons found there can sometimes save you quite a bit.


Question: I saw a television commercial for cold medicine that is safe for people with high blood pressure. I can’t remember what it was. Can you help me out?

Answer: The problem with multisymptom cold, flu and cough medicines is that they often contain decongestants. Ingredients such as phenylephrine or pseudoephedrine are vasoconstrictors. That means they narrow small blood vessels, which can in turn raise blood pressure.

Because pseudoephedrine (found in Sudafed and other products) can be used illicitly to make methamphetamine, it is no longer available on pharmacy shelves. Pseudoephedrine is sold “behind the counter” though, and does not require a prescription.

You may have seen a commercial for Coricidin HBP Cold & Flu. It contains acetaminophen to lower a fever and the antihistamine chlorpheniramine to help dry out nasal secretions. Other formulas contain dextromethorphan to calm a cough.

There are lots of cold remedies that do not contain the decongestant phenylephrine. They should not raise your blood pressure.

Whether any of them will actually speed recovery from an upper respiratory tract infection, though, remains controversial.

Joe Graedon is a pharmacologist; Dr. Teresa Graedon is a medical anthropologist and nutrition expert. Questions for the Graedons can be sent to them using their website,, or by writing to the following address: Graedons’ People’s Pharmacy, King Features, 628 Virginia Drive, Orlando, FL 32803.

The Tri-State Neighbor Weekly Update

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Joe Graedon is a pharmacologist; Dr. Teresa Graedon is a medical anthropologist and nutrition expert.

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