Are you hoarding hydroxychloroquine, dosing on dexamethasone or running around looking for remdesivir? Or alternately going down the herbal route with potions like the Kabasura Kudineer that Tamil Nadu is handing out, or even controversial Coronil from Baba Ramdev. Or are you just going to pop a paracetamol?Despite the many medicines being touted to tackle Covid, for most people it is that most common Over The Counter (OTC) product that they are likely to take. Paracetamol, or acetaminophen as it is known in some countries, is the world’s most popular pain-killer, and it has never been more in use.People who have, or think they have, a mild case of Covid are staying at home and taking it. And those who don’t want to be thought to have Covid are taking it too, like travellers who don’t want a temperature check to lead to them being quarantined, so they take a precautionary paracetamol just before they set out.Sudden demand for paracetamol has been taken to be a possible clue to people concealing Covid at home. In Tamil Nadu pharmacists were asked to submit details of people asking for paracetamol and cough syrups. Pharmacists pointed out, with justification, that to be effective such an order also had to apply to general retailers who could sell these as OTC products.It is hard to imagine how paracetamol’s origins lie in a mistakenly applied product and then years of neglect in the shadow of what was once the world’s top selling analgesic – aspirin. Diarmuid Jeffreys' book Aspirin: the Story of a Wonder Drug, also tells the story of paracetamol, the drug that would displace it.Aspirin is, in one sense, the older drug by far. Its key ingredient, acetylsalicylic acid, is found in willow trees and was used as a traditional anti-fever medicine for over 2,400 years. A more exotic source was castoreum, a secretion from beavers, probably because of their consumption of willow. But by the 19th century, medical science was looking for new sources for drugs.One of the most intensively studied substances at that time was coal tar, a by-product of the coal industry. It was while looking for an indigo dye that German chemists came up with a blue substance derived from coal tar that they named aniline, which was originally the name for an indigo yielding plant.In 1886 Arnold Cahn and Paul Hepp, two doctors in Strasbourg, had to treat a patient with intestinal worms, and ordered naphthalene which was the treatment at that time (we still use it as moth repellent). Their order got mixed up at the pharmacy, and what they got was a version of aniline called acetanilide. When they gave this to their patient it had no effect on the worms, but did reduce his fever very noticeably.Cahn and Hepp started selling this a drug which they called Antifebrine. This caught the attention of a dye-making company named Bayer, which realised it could produce a similar product, which it called Phenacetin. The success of these products woke Bayer up to the potential of analgesics and it decided to try and synthesise acetylsalicylic acid, whose value was known from ancient times, but had many problems in its natural form.Bayer called the product it came up with Aspirin, and this rapidly became the world’s most popular analgesic. Aniline products were sidelined, partly because they were thought to have toxic effects. But aspirin’s success lead to other companies making it too, in versions that differed enough from Bayer’s to enable them to claim it as new. Some of these even used aniline products – Anacin, for example, was originally aspirin plus acetanilide and caffeine – but the main ingredient was always aspirin.Bayer came back to the aniline products in the 1950s. The company was recovering from the taint of association with the Nazi regime, and desperately needed successful new products. This made them relook at older products, and they discovered that scientists had identified the really effective analgesic component of aniline drugs as a substance called N-acetyl-para-aminopherol. This was more manageably rechristened acetaminophen and was launched as Panadol in the UK.Aspirin might have seemed invulnerable then, but as Jeffreys notes, it was being undermined from its own side. Disprin, a soluble version of aspirin, was being marketed by Reckitt & Colman as less irritating to the stomach. Unfortunately, consumers concluded from this that aspirin was actually bad for the stomach, and this opened them up to other products.This was the breach that paracetamol stepped into and from which it has grown ever since. When McNeil, an American company later taken over by Johnson & Johnson (J&J), started selling a liquid version called Tylenol meant for children – sold in a cute red fire truck box – it cemented paracetamol’s image as the safe analgesic.This even survived the notorious incident in 1982 when bottles of Tylenol were adulterated by cyanide, killing seven people. J&J’s prompt action in recalling all Tylenol bottles simply served to build the brand. Today, the issue is the possible problems of paracetamol overdosing, like liver damage, and Covid has made these concerns even more acute. But as we sit at home, wondering if aches and fevers might be the virus, it looks like we will keep popping paracetamol.