Review question: in this review, we looked at the evidence for the interventions (treatments) used to treat people with paracetamol (acetaminophen) poisoning. Mainly, we tried to assess what effects the interventions had on the number of deaths and the need for a liver transplant.
Background: paracetamol is one of the most common drugs taken in overdose. Intentional or accidental poisoning with paracetamol is a common cause of liver injury.
Search date: the evidence is current to January 2017.
Study characteristics: randomised clinical trials (studies where people are randomly put into one of two or more treatment groups) where participants had come to medical attention because they had taken a paracetamol overdose, intentionally or by accident, regardless of the amount of paracetamol taken or the age, sex, or other medical conditions of the person involved.
There are many different interventions that can be used to try to treat people with paracetamol poisoning. These interventions include decreasing the absorption of the paracetamol ingested and hence decreasing the amount absorbed into the bloodstream. The agents include activated charcoal (that binds paracetamol together in the stomach), gastric lavage (stomach washout to remove as much paracetamol as possible), or ipecacuanha (a syrup that is swallowed and causes vomiting (being sick)). Paracetamol once absorbed into the bloodstream goes to the liver where the majority is broken down to harmless products. However, a small amount of the medicine is converted into a toxic product that the liver can normally handle but, when large amounts of paracetamol are taken, the liver is overwhelmed. As a consequence, the toxic product can damage the liver leading to liver failure, kidney failure, and in some cases death. Other interventions to treat paracetamol poisoning include medicines (antidotes) that may decrease the amount of the toxic products (such as a medicine called cimetidine) or breakdown the toxic products (including medicines called methionine, cysteamine, dimercaprol, or acetylcysteine). Finally, attempts can be made to remove paracetamol and its toxic products from the bloodstream using special blood cleansing equipment. All these treatments were examined.
We found 11 randomised clinical trials with 700 participants. Most of these trials looked at different treatments.
Key results: activated charcoal, gastric lavage, and ipecacuanha may reduce absorption of paracetamol if started within one to two hours of paracetamol ingestion, but the clinical benefit was unclear. Activated charcoal seems to be the best choice if the person is able to take it. People may not be able to take charcoal if they are drowsy and some may dislike its taste or texture (or both).
Of the treatments that remove the toxic products of paracetamol, acetylcysteine seems to reduce the rate of liver injury from paracetamol poisoning. Furthermore, it has fewer side effects than some other antidotes such as dimercaprol and cysteamine; its superiority to methionine was unclear. Acetylcysteine should be given to people with paracetamol poisoning at risk of liver damage, risk is determined by the dose ingested, time of ingestion, and investigations.
More recent clinical trials have looked at ways to decrease side effects of intravenous (into a vein) acetylcysteine treatment, by altering the way it is given. These trials have shown that by using a slower infusion and lower initial dose of acetylcysteine, the proportion of side effects such as nausea (feeling sick) and vomiting, and allergy (the body’s bad reaction to the medicine such as a rash) may be lowered.
Quality of the evidence: this review of interventions for paracetamol poisoning found surprisingly few published randomised clinical trials for this very common condition. Furthermore, the majority of trials had few participants and all were at high risk of bias. Accordingly, the quality of the evidence should be considered as low or very low.