Note: This document contains side effect information about acetaminophen / dextromethorphan / phenylephrine. Some dosage forms listed on this page may not apply to the brand name Theraflu Warming Relief Daytime Severe Cold & Cough.

Applies to acetaminophen / dextromethorphan / phenylephrine: oral capsule, oral tablet.

Serious side effects

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
• Not able to pass urine or change in how much urine is passed.
• A very bad skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may happen. It can cause very bad health problems that may not go away, and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.

Other side effects

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Dizziness.
• Feeling nervous and excitable.
• Trouble sleeping.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

For Healthcare Professionals

Applies to acetaminophen/dextromethorphan/phenylephrine: oral capsule, oral liquid, oral powder for reconstitution, oral suspension, oral syrup, oral tablet.

Hepatic

Very rare (less than 0.01%): Hepatic dysfunction (acetaminophen)^[Ref]

Nervous system

Serotonin syndrome has been reported with concomitant use of dextromethorphan and either a monoamine oxidase inhibitor (MAOI) or a serotonergic drug such as a selective serotonin reuptake inhibitor (SSRI). Serotonin syndrome causes changes in mental status, restlessness, myoclonus, hyperreflexia, diaphoresis, shivering, tremor, and hypertension.^[Ref]

Uncommon (0.1% to 1%): Drowsiness, dizziness, fatigue, dystonias (dextromethorphan)

Frequency not reported: Headache, dizziness, insomnia (phenylephrine)

Postmarketing reports: Serotonin syndrome (dextromethorphan)^[Ref]

Hypersensitivity

Rare (less than 0.1%): Allergic reactions (e.g. rash, urticaria, allergic dermatitis) (phenylephrine)

Very rare (less than 0.01%): Anaphylaxis, cutaneous hypersensitivity reactions (including skin rashes, angioedema, and Stevens Johnson syndrome) (acetaminophen)

Postmarketing reports: Allergic reactions (e.g. rash, urticaria, angioedema) (dextromethorphan)^[Ref]

Cardiovascular

Rare (less than 0.1%): Tachycardia, palpitations (phenylephrine)

Frequency not reported: Increased blood pressure, arrhythmias (phenylephrine)^[Ref]

Gastrointestinal

Uncommon (0.1% to 1%): Gastrointestinal disturbance, nausea, vomiting, abdominal discomfort, constipation (dextromethorphan)

Frequency not reported: Nausea, vomiting (phenylephrine)^[Ref]

Psychiatric

Frequency not reported: Nervousness, anxiety (phenylephrine)^[Ref]

Respiratory

Very rare (less than 0.01%): Bronchospasm (especially in patients sensitive to aspirin/other NSAIDs) (acetaminophen)^[Ref]

Genitourinary

Rare (less than 0.1%): Dysuria, urinary retention (phenylephrine)^[Ref]

Dysuria and urinary retention are most likely to occur with preexisting bladder outlet obstruction (e.g. prostatic hypertrophy)^[Ref]

Hematologic

Very rare (less than 0.01%): Thrombocytopenia (acetaminophen)^[Ref]

Ocular

Rare (less than 0.1%): Mydriasis, acute closure glaucoma (phenylephrine)^[Ref]

Phenylephrine is most likely to cause mydriasis and acute closure glaucoma in patients with pre-existing closed angle glaucoma.^[Ref]