Theraflu vs Dayquil For Coughs: Differences & Side Effects

Theraflu Flu & Sore Throat 

It is a combination of acetaminophen, pheniramine, and phenylephrine which relieves multiple cold and flu symptoms.

Phenylephrine is a decongestant which shrinks blood vessels in the nasal passages. Dilated blood vessels can cause nasal congestion.

Pheniramine is an antihistamine which reduces the natural chemical histamine in the body that can produce symptoms of sneezing, watery eyes, itching, and runny nose. Acetaminophen is a pain reliever and a fever reducer.


This medicine is typically used for reducing symptoms like pain, cough, fever, runny nose, sinus congestion, and sneezing caused by the flu or colds and upper respiratory infections.

Unlike other over-the-counter flu drugs, Tamiflu doesn’t just treat flu symptoms but it can shorten how long you have the flu, by inhibiting the growth of the virus.


Take the medicine every 4 hours, while symptoms persist.

Note – do not take more than 6 packets in 24 hours unless directed by a healthcare provider.

Side Effects and Precautions

Common side effects may include:

  • headaches;
  • constipation or diarrhea;
  • drowsiness;
  • upset stomach;
  • dizziness.

Rare side effects may include:

  • vomiting;
  • excitability;
  • weakness;
  • loss of appetite;
  • tightness in the chest;
  • nausea;
  • difficulty urinating or inability to urinate;
  • nervousness or anxiety;
  • hallucinations;
  • seizures;
  • rash;
  • confusion;
  • hives;
  • severe or persistent trouble sleeping;
  • itching;
  • severe nervousness, dizziness, or headaches;
  • difficulty breathing;
  • severe drowsiness;
  • swelling of the mouth, lips, face, or tongue;
  • vision changes;
  • irregular heartbeat;
  • tremor;
  • mental changes;
  • yellowing of the skin or eyes;
  • right-upper stomach pain;
  • persistent loss of appetite;
  • pale stools.


Avoid drinking alcohol since it may alter the way the medicines work. Furthermore, consuming alcoholic beverages may increase the risk of side effects.

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Drug Interactionsantibiotics pill

It may negatively interact with other medications, especially:

  • furazolidone;
  • anticoagulants (warfarin);
  • sodium oxybate (GHB);
  • digoxin or droxidopa;
  • reserpine;
  • beta-blockers (propranolol);
  • methyldopa;
  • catechol-o-methyltransferase (COMT) inhibitors;
  • mecamylamine;
  • indomethacin;
  • guanethidine;
  • MAOIs (phenelzine);
  • guanadrel;
  • tricyclic antidepressants (e.g., amitriptyline);
  • hydantoins (phenytoin).

Pregnancy & Breastfeeding

There are no well-done studies in women for determining the risk of using this medicine during pregnancy or while breastfeeding. Consult with your healthcare provider to weigh the potential benefits and risks before taking this medication.

Dayquil Cold & Flu

It is a combination of acetaminophen, dextromethorphan, and phenylephrine that is used for nasal congestion, sore throat, cough, headache, fever, minor aches and pains.

Phenylephrine belongs to a group of drugs called nasal decongestants, that shrink blood vessels in the nasal passages. Dilated blood vessels can cause nasal congestion.

Dextromethorphan is a cough suppressant that affects the signals in the brain which trigger the cough reflex.

Acetaminophen belongs to a group of drugs called analgesics, which are believed to work by blocking pain signals from reaching the brain.


This over-the-counter medication is used to treat the symptoms associated with a cold or the flu, including a sore throat, nasal congestion, cough, fever, headache, and minor aches and pains.

Note – it will not treat a cough which is caused by asthma, smoking, or emphysema.


4 doses in 24 hours are the maximum daily amount for this product.

Side Effects and Precautions

Common side effects may include:

  • upset stomach;
  • mild headache;
  • feeling nervous, irritable, restless, or anxious;
  • weakness;
  • sleep problems (insomnia);
  • dizziness;
  • dry nose, mouth, or throat;
  • diarrhea.

Rare side effects may include:

  • seizure (convulsions);
  • uneven heart rate;
  • little or no urinating;
  • jaundice (yellowing of the skin or eyes);
  • chest pain;
  • clay-colored stools;
  • hallucinations;
  • dark urine;
  • loss of appetite;
  • seizure;
  • confusion;
  • a feeling like you might pass out;
  • anxiety;
  • severe dizziness;
  • upper stomach pain;
  • mood changes;
  • buzzing in your ears;
  • blurred vision;
  • nausea;
  • dangerously high blood pressure.
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Ask a healthcare provider if it’s safe for you to take this drug if you have other medical conditions, particularly:

  • diabetes;
  • coronary artery disease;
  • chronic bronchitis;
  • liver disease;
  • glaucoma;
  • if you drink more than 3 alcoholic beverages per day;
  • overactive thyroid;
  • pheochromocytoma (an adrenal gland tumor);
  • heart disease;
  • bladder obstruction;
  • high blood pressure;
  • emphysema;
  • epilepsy or other seizure disorder;
  • a cough caused by smoking;
  • a cough with mucus;
  • asthma or chronic obstructive pulmonary disease.


Avoid drinking alcoholic beverages since alcohol may increase the risk of liver damage or other side effects.

Drug Interactions

It may negatively interact with other medications, especially:

  • melatonin;
  • Aleve (naproxen);
  • prednisone;
  • Benadryl (diphenhydramine);
  • Tylenol (acetaminophen);
  • ibuprofen;
  • eligard;
  • Relief (phenylephrine ophthalmic);
  • omeprazole;
  • alka seltzer;
  • naproxen.

Pregnancy & BreastfeedingGood For Pregnant Women

This medication may pass into breast milk and can negatively affect an infant. In addition, it may slow breast milk production. Do not use this drug without a healthcare professional’s advice if you are breastfeeding an infant.

Moreover, it is not known precisely whether this medication will harm the fetus. Do not use this medicine without a doctor’s advice if you are pregnant.

Bottom Line – Theraflu vs Dayquil

Theraflu Flu & Sore Throat (active ingredients – acetaminophen, pheniramine, and phenylephrine) is a combination medicine which is used to treat headaches, stuffy nose, runny nose, sneezing, sinus congestion, or watery eyes, caused by allergies, the common cold, or the flu.

DayQuil Cold & Flu (active ingredients – acetaminophen, dextromethorphan, and phenylephrine) is a combination medicine that is used to treat headaches, stuffy nose, fever, body aches, cough, and sinus congestion caused by allergies, the common cold, or the flu.

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In conclusion, both medicines are useful in treating cold and flu symptoms but they have plenty of side effects.

For instance, according to New Zealand researchers, over-the-counter cold remedies which combine acetaminophen with phenylephrine can bring on serious side effects, including dangerously high blood pressure, an irregular heartbeat, and tremors.


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