Patients are often asymptomatic or have only mild gastrointestinal symptoms at initial presentation. Untreated paracetamol poisoning may cause varying degrees of liver injury over the 2 to 4 days following ingestion, including fulminant hepatic failure.
Rarely, massive overdose may initially present with coma and severe metabolic acidosis. Presentation with coma may also occur if a combination preparation of paracetamol and opioid is taken in overdose, or after an overdose of multiple drugs.
Hepatotoxicity is extremely rare in patients treated with acetylcysteine within 8 hours of an acute paracetamol overdose. The efficacy of acetylcysteine decreases subsequent to the first 8 hours following an acute paracetamol overdose, with a corresponding stepwise increase in hepatotoxicity with increasing treatment delays between 8 and 16 hours.
The recommended therapeutic dose of paracetamol depends on age. Management of paracetamol poisoning. Acute overdose: excessive amounts of paracetamol ingested over a period of less than 1 hour; usually in the context of self-harm. Staggered overdose: excessive amounts of paracetamol ingested over longer than 1 hour; usually in the context of self-harm. Excessive paracetamol taken with intent to treat pain or fever and without self-harm intent.
Can involve use of excessive doses of the same paracetamol product or inadvertent use of more than one paracetamol-containing product at the same time. The NPIS recommends that, for the purposes of calculating potentially toxic doses, the following be considered: [2] National Poisons Information Service. For pregnant patients, the toxic dose is calculated using the patient's pre-pregnancy weight.
The researchers told the British Journal of Clinical Pharmacology that this life-threatening condition could be easily missed by doctors and patients. Doctors may not initially spot the problem because blood tests will not show the staggeringly high levels of paracetamol seen with a conventional overdose, where someone may have swallowed several packets of the drug.
Patients who have taken a staggered overdose tend to fare worse than those who have taken a large overdose, the study suggests. Dr Kenneth Simpson and colleagues looked at the medical records of patients who had been referred with paracetamol-induced liver injury to the Scottish Liver Transplantation Unit at the university hospital.
The who had taken a staggered overdose were more likely to develop liver and brain problems and need kidney dialysis or help with their breathing. They were also more likely to die of their complications. In some, the act of taking an overdose is a spur-of-the-moment thing, whilst in others it can be pre-planned.
Those who have pre-planned may have stockpiled medication, sorted out their affairs such as writing a will and also written a suicide note. Some people take higher-than-recommended doses of paracetamol for pain over several days. They may not intend to kill themselves, and occasionally may not even realise they are harming themselves until they begin to feel unwell.
Paracetamol is widely available from shops and is present in most homes. The government has made rules to limit how much can be bought in one go, which may help reduce the number of overdoses. It is reasonably easy to take and so the government had also ruled that it should only be available in blister packs which can mean the tablets are trickier to get out. There may be no symptoms for the first day. A feeling of sickness nausea and being sick vomiting may occur a few hours after taking the overdose.
After 24 hours there may be pain under the ribs on the right side where the liver is and there may be yellowing of the whites of the eyes and the skin jaundice.
Other features include:. Sometimes it is carers who will discover that someone has taken an overdose. They may find empty packets or a suicide note. It is important to bring the empty packets and notes with you to the hospital. They will also undertake a full examination which early on may not find anything. Once liver damage sets in there may be jaundice, a tender liver and presence of brain involvement called encephalopathy.
Other tests that are requested will depend on each individual case and the patient's course. For example, if other medications were taken then their levels may need to be checked. Immediate management will require resuscitation and stabilisation. If the patient is unstable - such as having low blood pressure - or there is overwhelming liver failure, they will need to be treated on an intensive care unit. The paracetamol levels will be sent off and once the result is back this is compared with a standard graph - patients who are above a certain line will need treatment.
Those below the line may not require treatment. Treatment is with intravenous N-acetylcysteine NAC and is given to all who have high paracetamol levels. If there is any doubt about the time of the overdose or there has been a 'staggered overdose', intravenous NAC is started without delay.
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