Harvard Health Letter

Could a cold remedy make you sicker?


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Cold remedies may interact with other
medications you're already taking.
Talk to a pharmacist if you're unsure.

Over-the-counter painkillers, decongestants, antihistamines, and combination remedies can sometimes cause other health problems.

It's handy to walk into a drugstore for an over-the-counter (OTC) cold remedy. But some of the ingredients may cause adverse reactions. "I think people underestimate these medications because you can get them without a prescription. But they are still medications that can interact with other drugs and interfere with existing health problems," says Laura Carr, a pharmacist at Harvard-affiliated Massachusetts General Hospital.

It's crucial to read the active ingredient list of any OTC medication you consider taking, and talk to your pharmacist or doctor if you're not sure how it may affect you. Carr recommends that older adults pay close attention to the following.

Decongestants

  • What to look for: pseudoephedrine (Sudafed) or phenylephrine (Neo-Synephrine, Sudafed PE Nasal Decongestant)

  • How they help: Decongestants narrow the blood vessels, which can help reduce inflammation in your nasal passages and provide relief.

  • The risk: They can increase your blood pressure. Decongestants are also stimulants, which can increase your heart rate or cause anxiety or insomnia. The drugs aren't recommended for people with heart disease, high blood pressure, diabetes, or angina. Prolonged use of OTC decongestant nasal sprays can lead to greater swelling than you experienced initially.

  • What to do: "Check with your doctor or pharmacist before using them, as older adults can be more sensitive to the effects of these medicines," says Carr.

Acetaminophen

  • What to look for: acetaminophen (Tylenol)

  • How it helps: Acetaminophen relieves pain and reduces fevers.

  • The risk: Too much acetaminophen can be toxic to your liver, and alcohol can increase the toxicity. "Too much" is generally defined as more than 3,000 to 4,000 milligrams (mg) per day. Acetaminophen is a frequent ingredient in many pain relievers and cold remedies, and taking more than one cold remedy may mean you're taking too much acetaminophen.

  • What to do: "Do not take more than the recommended dose listed on the product. For example, if you have a cold remedy with 325 mg per tablet, you shouldn't take more than 10 pills in a day," says Carr. "And don't take high doses for several days. That's also been shown to harm your liver." If you're taking a combination drug, check the ingredients for acetaminophen. If it's listed, don't take separate acetaminophen pills to relieve pain, including prescription pain relievers. Don't drink alcohol while taking acetaminophen.

Antihistamines

  • What to look for: diphenhydramine (Benadryl, Unisom Sleep Gels), chlorpheniramine (Chlor-Trimeton), and doxylamine (Unisom)

  • How they help: Antihistamines decrease the production of histamine, a substance that leads to a runny nose, watery eyes, and sneezing. They also have a sedative effect and are frequently found in nighttime cold remedies to help you sleep.

  • The risk: Older adults don't metabolize this medication well. "If you take it at night, you might still feel groggy and confused in the morning, which can lead to falls and injuries. Then if you take more of the medication, there's an accumulation that makes the confusion and sedation even worse," says Carr. Antihistamines can also cause the retention of urine in the bladder, which can lead to urinary tract infections.

  • What to do: "Avoid medications with antihistamines, unless your doctor gives you approval to take them," recommends Carr. Most nighttime cold or pain remedies contain an antihistamine, so be sure to check the list of ingredients.

Combination medicines

  • What to look for: Dayquil, Nyquil, Tylenol Cold and Flu, Advil Cold and Sinus, or any cold remedy that treats more than one symptom

  • How they help: For convenience, these have two to four medications in one dose, such as a painkiller (acetaminophen, ibuprofen), a cough suppressant (dextromethorphan), and a decongestant (phenylephrine).

  • The risk: You may not need all of the medications. "Treating symptoms you don't have exposes you to medicine you don't need, and that puts you at risk for possible side effects unnecessarily," says Carr.

  • What to do: Look at the ingredient lists of potential OTC cold remedies, and make sure you select the one that treats only your symptoms and has only ingredients that are safe for you to use. If you are unsure which combination product is right for you, make sure you ask a pharmacist or your doctor for advice.