Paracetamol, known in the United States as acetaminophen, is an analgesic and antipyretic drug commonly used to treat pain, headaches and fever. It is widely available over the counter, either by itself or as a component in cold and flu remedies. Like many medications, taking too much paracetamol can be very dangerous. In many countries, sales of paracetamol are limited in order to counteract the risk of paracetamol overdose. The dangers of paracetamol overdose are widely believed to be exacerbated by some combinations of paracetamol and alcohol, but medical evidence does not appear to support this claim.
The danger posed by paracetamol is paracetamol toxicity, which can cause severe liver damage. When the human body metabolizes paracetamol, it produces N-acetyl-p-benzoquinoneimine or NAPQI, a toxin capable of destroying liver cells and depleting the liver's natural level of glutathione, an antioxidant. However, this toxin is normally only produced in small amounts. When an individual overdoses on paracetamol, more NAPQI is produced than the liver can detoxify, resulting in abdominal pain, nausea and eventually even death. If paracetamol toxicity is identified early, it can be treated, but if it goes unnoticed the risks are very great.
Many people believe that taking paracetamol while drinking can cause liver damage. In fact, taking paracetamol within the recommended dosage while drinking does not increase the risk of toxicity. Even combining alcohol with a paracetamol overdose does not appear to increase the risk of serious harm, although the risk of paracetamol toxicity from the overdose remains serious.
Some doctors have suggested, based on tests conducted on animals, that paracetamol toxicity can be exacerbated by chronic excessive alcohol consumption. According to this theory, chronic alcohol abuse produces large quantities of the enzyme CYP2E1, which helps the production of toxins from paracetamol. Despite the fact that this belief is widespread, the evidence for it is ambiguous.
Articles published in the medical journals Critical Care, Drug Safety and the British Journal of Clinical Pharmacology have argued that despite some evidence that long-term alcohol abuse increases paracetamol toxicity, there is no evidence that the combination of paracetamol and alcohol increases the danger of toxicity in humans. The liver damage observed in chronic alcohol abusers who had taken paracetamol overdoses was also observed in those who did not consume excessive alcohol. Therefore, despite the widespread belief that paracetamol and alcohol have negative interactions, the clinical evidence to substantiate this belief appears to be lacking.