Tylenol (acetaminophen) Side Effects, Warnings, and Interactions

Tylenol (acetaminophen) is an analgesic and antipyretic to relieve fever, aches, and pains. It may be used for conditions such as mild arthritis, but it does not reduce inflammation, redness, or swelling of the joint. Tylenol is as effective as aspirin for pain relief when inflammation is not present. It is also comparable to ibuprofen in relieving pain caused by osteoarthritis of the knee. Side effects with appropriate use of Tylenol are rare.

The side effects of Tylenol may include rash, nausea, and headache.

Other important side effects of Tylenol include:

• hypersensitivity reactions
• serious skin reactions
• kidney damage
• anemia
• low platelets in the blood (thrombocytopenia)

Chronic alcohol use can increase the risk of stomach bleeding. The most serious side effect of Tylenol is liver damage due to large doses, chronic use, or concomitant use with alcohol or other drugs that also harm the liver. Additional serious side effects of Tylenol include:

• bleeding in the intestines and stomach
• angioedema
• Stevens-Johnson syndrome
• kidney damage
• reduced white blood cell counts

Tylenol is often used during pregnancy for short-term treatment of fever and minor pain. It is excreted in breast milk in small amounts, but it appears to be safe for use by nursing mothers.

What are the important side effects of Tylenol (acetaminophen)?

Side effects with appropriate use of acetaminophen are rare.

The most common side effects are rash, nausea, and headache.

Other important side effects include:

• Hypersensitivity reactions
• Serious skin reactions
• Kidney damage
• Anemia
• Reduced number of platelets in the blood (thrombocytopenia)

Chronic alcohol use can increase the risk of stomach bleeding. The most serious side effect is liver damage due to large doses, chronic use, or concomitant use with alcohol or other drugs that also harm the liver.

Other serious side effects that have been reported include bleeding in the intestines and stomach, angioedema, Stevens-Johnson syndrome, kidney damage, and reduced white blood cell counts.

Tylenol (acetaminophen) side effects list for healthcare professionals

The following serious adverse reactions are discussed elsewhere in the labeling:

• Hepatic Injury
• Serious Skin Reactions
• Allergy and Hypersensitivity

Clinical Trial Experience

Because clinical trials are conducted under varying conditions, adverse reaction rates observed cannot be directly compared to rates in other clinical trials and may not reflect the rates observed in practice.

Adult Population

A total of 1,020 adult patients have received acetaminophen in clinical trials. Most patients were treated with acetaminophen 1,000 mg every 6 hours. All adverse reactions that occurred in adult patients treated with acetaminophen or placebo in repeated dose, placebo-controlled clinical trials at an incidence = 3% and at a greater frequency than placebo are listed in Table 3. The most common adverse events in adult patients treated with acetaminophen (incidence = 5% and greater than placebo) were nausea, vomiting, headache, and insomnia.

Other Adverse Reactions Observed During Clinical Studies of Acetaminophen in Adults

The following additional treatment-emergent adverse reactions were reported by adult subjects treated with acetaminophen in all clinical trials (n=1,020) that occurred with an incidence of at least 1% and at a frequency greater than placebo (n=525).

Blood and lymphatic system disorders: anemia

General disorders and administration site conditions: fatigue, infusion site pain, edema peripheral

Investigations: aspartate aminotransferase increased, breath sounds abnormal

Metabolism and nutrition disorders: hypokalemia

Musculoskeletal and connective tissue disorders: muscle spasms, trismus

Psychiatric disorders: anxiety

Respiratory, thoracic and mediastinal disorders: dyspnea

Pediatric Population

A total of 355 pediatric patients have received acetaminophen in clinical trials. Pediatric patients received acetaminophen doses up to 15 mg/kg on a schedule of every 4 hours, every 6 hours, or every 8 hours. The most common adverse events (incidence = 5%) in pediatric patients treated with acetaminophen were nausea, vomiting, constipation, pruritus, agitation, and atelectasis.

Other Adverse Reactions Observed During Clinical Studies of Acetaminophen in Pediatrics

The following additional treatment-emergent adverse reactions were reported by pediatric subjects treated with acetaminophen (n=355) that occurred with an incidence of at least 1%.

Blood and lymphatic system disorders: anemia

Cardiac disorders: tachycardia

Gastrointestinal disorders: abdominal pain, diarrhea

General disorders and administration site conditions: injection site pain, edema peripheral, pyrexia

Investigations: hepatic enzyme increase

Metabolism and nutrition disorders: hypoalbuminemia, hypokalemia, hypomagnesemia, hypophosphatemia, hypervolemia

Musculoskeletal and connective tissue disorders: muscle spasm, pain in extremity

Nervous system disorders: headache

Psychiatric disorders: insomnia

Renal and urinary disorders: oliguria

Respiratory, thoracic and mediastinal disorders: pulmonary edema, hypoxia, pleural effusion, stridor, wheezing

Skin and subcutaneous tissue disorders: periorbital edema, rash

What drugs interact with Tylenol (Acetaminophen)?

Effects of Other Substances on Acetaminophen

Substances that induce or regulate hepatic cytochrome enzyme CYP2E1 may alter the metabolism of acetaminophen and increase its hepatotoxic potential. The clinical consequences of these effects have not been established. Effects of ethanol are complex, because excessive alcohol usage can induce hepatic cytochromes, but ethanol also acts as a competitive inhibitor of the metabolism of acetaminophen.

Anticoagulants

Chronic oral acetaminophen use at a dose of 4,000 mg/day has been shown to cause an increase in international normalized ratio (INR) in some patients who have been stabilized on sodium warfarin as an anticoagulant. As no studies have been performed evaluating the short-term use of acetaminophen in patients on oral anticoagulants, more frequent assessment of INR may be appropriate in such circumstances.

Summary

Tylenol (acetaminophen) is an analgesic and antipyretic to relieve fever, aches, and pains. It may be used for conditions such as mild arthritis, but it does not reduce inflammation, redness, or swelling of the joint. Side effects with appropriate use of Tylenol are rare.