When was acetaminophen invented

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Last updated: April 17, 2026

Quick Answer: Acetaminophen was first synthesized in 1877 by American chemist Harmon Northrop Morse. It was not widely used until it was rediscovered and introduced in the 1950s under brand names like Tylenol.

Key Facts

Acetaminophen was first synthesized in 1877 by Harmon Northrop Morse
It was rediscovered in 1948 during research at the University of Pennsylvania
Tylenol, the first major brand, was introduced in the U.S. in 1955
It became available over-the-counter in 1960 without a prescription
Acetaminophen is now found in over 600 medications in the U.S.

Overview

Acetaminophen, also known as paracetamol outside the U.S., is one of the most widely used over-the-counter pain relievers and fever reducers in the world. Though its widespread use began in the mid-20th century, its origins trace back to the late 19th century.

Initially overlooked, acetaminophen was rediscovered decades later and eventually became a staple in medicine cabinets globally. Its safety profile, when used correctly, and effectiveness in treating mild to moderate pain made it a preferred alternative to aspirin.

First synthesis in 1877 by American chemist Harmon Northrop Morse during experiments with acetanilide and coal-tar derivatives.
Not immediately adopted due to limited understanding of its benefits and the dominance of other analgesics like aspirin at the time.
Rediscovered in 1948 by Bernard Brodie and Julius Axelrod, who identified it as the active metabolite of acetanilide and phenacetin.
Introduced in prescription form in 1950 under the brand name Panadol in the UK, primarily for post-surgical pain.
Launched in the U.S. in 1955 as Tylenol Children’s Elixir, marketed for children due to its gentler gastrointestinal profile than aspirin.

How It Works

Acetaminophen functions differently from nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, making it a unique option for pain and fever management.

Mechanism of action:It inhibits COX enzymes in the central nervous system, reducing prostaglandin production and lowering pain and fever signals.
Metabolism:Processed primarily in the liver by glucuronidation and sulfation; a small fraction becomes toxic if overdose occurs.
Onset of effect:Takes 30–60 minutes to begin working after oral administration, with peak levels in about 1–2 hours.
Dosage limits:Maximum daily dose is 4,000 mg for adults, though lower limits are recommended for long-term use.
Side effects:Liver damage is the primary risk, especially when combined with alcohol or taken in excess of recommended doses.
Drug interactions:Enhances effects of warfarin and other anticoagulants, increasing bleeding risk even at therapeutic doses.

Comparison at a Glance

Here’s how acetaminophen compares to other common pain relievers:

Medication	Introduced	Primary Use	Key Risk	OTC Since
Acetaminophen	1877 (synthesized), 1955 (U.S. market)	Pain, fever	Liver toxicity	1960
Aspirin	1899	Pain, inflammation, antiplatelet	GI bleeding	1899
Ibuprofen	1961	Pain, inflammation	Stomach ulcers	1984
Naproxen	1976	Pain, inflammation	Kidney damage	1994
Codeine (combination)	1950s	Moderate pain	Dependence, drowsiness	Prescription only

This table highlights that while acetaminophen lacks anti-inflammatory properties, its safety for children and lower gastrointestinal risk made it ideal for widespread use. Unlike aspirin, it doesn’t increase bleeding risk, making it safer for many patients.

Why It Matters

Acetaminophen’s development marked a turning point in accessible, safe pain management, particularly for vulnerable populations like children and those with gastrointestinal sensitivities.

Available in over 600 products, including cold and flu formulations, making it one of the most common active ingredients in OTC medicine.
Recommended for children due to its lower risk of Reye’s syndrome compared to aspirin.
Used in hospitals for postoperative pain and fever control, often preferred in surgical recovery units.
Global impact: Sold in over 100 countries, with annual sales exceeding $1.5 billion worldwide.
Public health concern: Acetaminophen overdose is a leading cause of acute liver failure in the U.S., prompting FDA warnings.
Regulatory changes: In 2011, the FDA limited prescription combinations to 325 mg per dose to reduce overdose risk.

Today, acetaminophen remains a cornerstone of modern medicine, balancing efficacy with safety when used responsibly. Its history reflects both scientific persistence and the importance of pharmacovigilance in drug development.