Acetaminophen / Dextromethorphan / Diphenhydramine / Phenylephrine Side Effects
Medically reviewed by Drugs.com. Last updated on Mar 7, 2025.
Applies to acetaminophen / dextromethorphan / diphenhydramine / phenylephrine: oral tablet, oral tablet extended release.
Important warnings
This medicine can cause some serious health issues
Do not use this medicine if you have taken an MAO inhibitor in the past 14 days.
A dangerous drug interaction could occur.
MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.
Do not take more of this medication than is recommended. An overdose of acetaminophen can damage your liver or cause death. Call your doctor at once if you have nausea, pain in your upper stomach, itching, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of your skin or eyes).
In rare cases, acetaminophen may cause a severe skin reaction. Stop taking this medicine and call your doctor right away if you have skin redness or a rash that spreads and causes blistering and peeling.
Get emergency medical help if you have any of these signs of an allergic reaction while taking acetaminophen / dextromethorphan / diphenhydramine / phenylephrine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
In rare cases, acetaminophen may cause a severe skin reaction that can be fatal. This could occur even if you have taken acetaminophen in the past and had no reaction. Stop taking this medicine and call your doctor right away if you have skin redness or a rash that spreads and causes blistering and peeling. If you have this type of reaction, you should never again take any medicine that contains acetaminophen.
Stop using this medicine and call your doctor at once if you have:
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fast, slow, or uneven heart rate;
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chest pain, rapid pulse, feeling like you might pass out;
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severe dizziness or anxiety, mood changes, confusion, hallucinations;
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little or no urinating;
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nausea, pain in your upper stomach, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of your skin or eyes); or
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dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, seizure).
Common side effects may include:
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dizziness, drowsiness, mild headache;
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dry mouth, nose, or throat;
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constipation, diarrhea, upset stomach;
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blurred vision;
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feeling restless or irritable; or
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sleep problems (insomnia).
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.
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More about acetaminophen / dextromethorphan / diphenhydramine / phenylephrine
- Check interactions
- Compare alternatives
- Dosage information
- Drug class: upper respiratory combinations
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Further information
Acetaminophen/dextromethorphan/diphenhydramine/phenylephrine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.