What are the active ingredients in Tylenol PM?

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Tylenol PM Active Ingredients

Tylenol PM contains two active ingredients: acetaminophen 500 mg (pain reliever/fever reducer) and diphenhydramine HCl 25 mg (antihistamine/sleep aid).

Active Ingredient Details

Acetaminophen Component

  • Acetaminophen 500 mg serves as the analgesic and antipyretic component 1
  • Functions through multiple mechanisms including cyclooxygenase inhibition and effects on the endocannabinoid system 2
  • Maximum daily dose should not exceed 3000-4000 mg from all sources combined 3

Diphenhydramine Component

  • Diphenhydramine HCl 25 mg is the sedating antihistamine that promotes sleep 4
  • Acts as the primary sleep-inducing agent in over-the-counter sleep medications 4
  • Causes drowsiness through antihistamine effects on the central nervous system 4

Critical Safety Considerations

Acetaminophen Dosing Warnings

  • Risk of unintentional overdose is substantial when combining multiple acetaminophen-containing products 5
  • 45.6% of adults demonstrate they would overdose by "double-dipping" with two acetaminophen products simultaneously 5
  • Confusion exists regarding maximum daily dosing, with recommendations ranging from 3000-4000 mg depending on tablet strength and manufacturer 3
  • Severe hepatotoxicity can occur with overdose, though early treatment with N-acetylcysteine prevents liver damage 1

Antihistamine Precautions

  • Not recommended during pregnancy or nursing 4
  • Use with caution in elderly patients due to increased risk of falls and cognitive impairment 4
  • Additive sedative effects occur when combined with other CNS depressants or alcohol 4
  • Contraindicated in patients with narrow-angle glaucoma, urinary retention, or severe respiratory compromise 4

Common Pitfalls to Avoid

  • Never combine Tylenol PM with other acetaminophen products including prescription combinations with opioids (hydrocodone/acetaminophen, oxycodone/acetaminophen, codeine/acetaminophen) 4
  • Check all current medications for hidden acetaminophen content, as over 200 million acetaminophen-containing prescriptions are dispensed annually 3
  • Avoid use in patients already taking sedating medications including benzodiazepines, opioids, or other antihistamines 4
  • Limited literacy patients face 1.65 times higher risk of acetaminophen overdose errors 5

References

1
Research

Paracetamol: past, present, and future.

American journal of therapeutics, 2000

2
Research

Paracetamol - An old drug with new mechanisms of action.

Clinical and experimental pharmacology & physiology, 2021

4
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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