Paracetamol Made Out of Coal Tar – How Safe Is It?

From headaches to menstrual pain, muscle pain to back pain, arthritis, toothache, and the common cold and flu, Paracetamol works on everything. It is a great fever reducer and pain reliever. Do you know the funny thing about Paracetamol? It doesn't actually cure anything. And yet, in 2023 alone, 145 thousand tons of Paracetamol were sold around the world.

Paracetamol is effective in managing symptoms for a wide range of ailments. Billions of people take several doses each year of this medicine, also sold under the aegis of different brands like Tylenol, Panadol, and Calpol. You might also find Paracetamol in combination with other drugs present in Excedrin and NyQuil.

And that's not it. Paracetamol is also found in many other drugs, either in combination or in different shapes and forms. It's the world of Paracetamol, and we're just paying rent. But when was this wonder drug introduced into our lives, and what is its genesis?

Paracetamol first became used in 1893, became a prescription drug in the US in 1951, and became an OTC drug in 1955. But if you want to find out about its origins, you'll have to go way back. As early as ancient and medieval times, known antipyretic agents were compounds in white willow bark (salicins, basically aspirin) and cinchona bark. Attempts to refine and isolate salicin and salicylic acid occurred through the middle and late 19th century. But the cinchona tree wasn't going to last forever. When it became scarce in the 1880s, people began looking for alternatives.

Paracetamol, in its initial form, was derived from coal tar. The coal mining industry was booming, and the scientists were using the biproducts for research. Coal tar was refined to extract aniline, an aromatic amine. Chemists then used distillation and purification to isolate aniline from coal tar.

Late in the 19th century, aniline was used as a starting point to synthesize different derivatives, one among them being Paracetamol. Specifically, it involves the acetylation of p-aminophenol, which is related to aniline. Early paracetamol synthesis involved converting aniline to p-aminophenol, which was acetylated to form Paracetamol.

However, that is not the only way the drug was developed. In 1873, American chemist Harmon Northrop Morse synthesized Paracetamol by reducing p-nitrophenol with tin in glacial acetic acid.

But It was not until 1948 that Gerad R.A. Laurence and Walter M.G. Freeman were among the first to study and document this drug's analgesic and antipyretic properties, becoming widely known as a medical compound. In 1946, the Institute for the Study of Analgesic and Sedative Drugs gave the New York City Department of Health a grant to study the issues associated with analgesic agents.

Military strategist Bernard Brodie and future Nobel Prize winner Julius Axelrod were asked to find out why non-aspirin agents were associated with the development of methemoglobinemia, a potentially lethal condition that decreases the oxygen-carrying capacity of blood.

In 1948, the duo, with Dr. Frederick Flinn, linked acetanilide with methemoglobinemia and discovered that the analgesic effect of acetanilide was because of Paracetamol, its active metabolite. Three years later, the pharmaceutical company McNeil Laboratories (now a part of Johnson & Johnson) launched Tylenol, the brand name for acetaminophen.

From then on, it became widely commercially used. A few years later, in the 1960s, it started becoming a popular alternative to aspirin because of its low risk of causing irritation and bleeding in the stomach. This is when it began to be included in different over-the-counter medications.

Now that we have discussed the entire history of the drug, we can safely say that no coal miner stumbled upon a Paracetamol tablet in the middle of a coal mine. Then why are we discussing its relation with something that has no apparent semblance to the drug?

Coal tar is a byproduct of coal carbonization, and early pharmaceuticals, including many painkillers, were developed from it. Coal tar was a common source of various organic compounds in the 19th and early 20th centuries. Although its early development involved coal tar, contemporary production of Paracetamol does not use coal tar directly.

Coal tar, used historically in some medical treatments, is different from Paracetamol. You're more likely to have side effects if you use more than the recommended amount or use it more often than recommended.

Skin irritation- Research on coal tar treatments has reported that about 10-15% of patients may experience skin irritation.

Increased sensitivity to sunlight (photosensitivity)- In clinical practice, around 5-10% of patients using coal tar-based treatments might report some degree of photosensitivity.

Hair color changes— Specific incidence rates are not widely available, but hair color changes are less frequently reported than other side effects like skin irritation or photosensitivity. When they do occur, they are often reported in the context of prolonged use of coal tar shampoos or topical treatments.

Coming back to Paracetamol today, however, it is synthesized using more refined methods. It often starts with p-aminophenol - a chemical compound. This is a crucial intermediate in the synthesis of Paracetamol and is derived through a process involving the chemical reduction of nitrobenzene.

This compound is derived from benzene through nitration and has the chemical formula C₆H₅NO₂. A reduction process then converts nitrobenzene to p-aminophenol. The exact process involves converting the nitro group (-NO₂) on nitrobenzene to an amino group (-NH₂), resulting in p-aminophenol. This reduction can be performed through

Catalytic Hydrogenation - In which nitrobenzene is treated with hydrogen gas in the presence of a catalyst like palladium or platinum, to produce p-aminophenol.

Chemical reducing agents - Nitrobenzene may be reduced using chemical reducing agents like iron and hydrochloric acid, or sodium dithionite, to produce p-aminophenol, which is purified through filtration and crystallisation - by dissolving the crude product in a solvent and cooling it to obtain pure p-aminophenol crystals. The vital step in synthesising Paracetamol is the acetylation of p-aminophenol by reacting the chemical with acetic anhydride or acetyl chloride to form Paracetamol with acetic acid as a byproduct.

Coal tar refers to a complex mixture derived from the carbonisation of coal, containing different organic compounds, including polycyclic aromatic hydrocarbons (PAHs), phenols, and other tarry substances aligned with carbon (C), hydrogen (H), and oxygen (O) among others. Paracetamol, on the other hand, is a single chemical compound with the formula C₈H₉NO₂. It is a refined substance with well-defined properties and uses.

Despite coal tar's early prevalence in early medicine, Paracetamol was synthesized separately from coal tar and developed as a distinct chemical entity. Modern Paracetamol is produced from refined chemicals, specifically p-aminophenol. Paracetamol's modern synthesis avoids the complexities and potential risks associated with coal tar.

Paracetamol is a widely used analgesic that doesn't harm you until you take too much of it, which can lead to liver damage. It is used to tackle the symptoms of a litany of problems, from pain and fever to toothaches and menstrual cramps and everything in between.

Rest assured, coal tar is not used to produce pain relief medication, at least not directly. If you still have a headache, take a P650 and go about your day.