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Acetaminophen / caffeine / phenyltoloxamine Side Effects

For the Consumer

Applies to acetaminophen / caffeine / phenyltoloxamine: oral capsule

Get emergency medical help if you have any of these signs of an allergic reaction while taking acetaminophen / caffeine / phenyltoloxamine: 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:

  • fast or pounding heartbeat;

  • easy bruising or bleeding, unusual weakness;

  • bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds;

  • trouble swallowing, increased thirst and urination;

  • severe diarrhea or stomach pain;

  • confusion, ringing in your ears, hearing problems;

  • a light-headed feeling, like you might pass out;

  • little or no urinating;

  • muscle weakness, loss of coordination; or

  • nausea, pain in your upper stomach, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of your skin or eyes).

Common side effects may include:

  • dizziness, drowsiness, memory problems;

  • nervous feeling, sleep problems (insomnia);

  • blurred vision, dry mouth, nose or throat;

  • upset stomach, constipation; or

  • mild itching or skin rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to acetaminophen / caffeine / phenyltoloxamine: oral capsule


Cardiovascular side effects have included palpitations, hypotension, and cardiac stimulation.[Ref]


Gastrointestinal side effects have included epigastric distress, diarrhea, intestinal cramps, nausea, xerostomia, and dryness of mouth, throat, and nose.[Ref]


Dermatologic side effects have included urticaria and rash. Acetaminophen has been associated with a risk of rare but potentially fatal serious skin reactions know as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP).[Ref]


Hypersensitivity side effects have included allergic reactions.[Ref]


Hematologic side effects have included thrombocytopenia and agranulocytosis.[Ref]


Musculoskeletal side effects have included muscular weakness.[Ref]


Genitourinary side effects have included urinary retention.[Ref]

Nervous system

Nervous system side effects have included dizziness, drowsiness, disturbed coordination, inability to concentrate, insomnia, tremors, nervousness, convulsions, irritability, and dependence.[Ref]


Ocular side effects have included blurred vision.[Ref]


Renal side effects have included nephrotoxicity.[Ref]


Metabolic side effects have included hyperglycemia.[Ref]


1. "Product Information. Flextra (APAP/caffeine/phenyltoloxamine)." Poly Pharmaceuticals Inc, Quitman, MS.

Not all side effects for acetaminophen / caffeine / phenyltoloxamine may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.