Paracetamol self-poisoning: when oral N-acetylcysteine saves life? a case report

Paracetamol is the most widely drug involved in accidental paediatric exposures and deliberate self-poisoning cases because of its availability. N-acetyl cystein is the main treatment for this poisoning. We report a case of a 24-year-old Arab female who has deliberately ingested 100 tablets of 500 mg paracetamol each (50g). Her first examination was normal. She has received oral N-acetyl cystein (NAC) 6 hours after the ingestion. Serum paracetamol level done 18 hours post ingestion was 900 mg/l. On review the next days, she did not develop any symptoms of liver failure. However, due to the massive paracetamol ingestion associated with high serum paracetamol levels, oral NAC was continued for 3 days. The patient was discharged well on the fifth day of hospitalization. Our patient has ingested one of the highest paracetamol overdose (50g) with the highest paracetamol blood levels ever reported in medical literature. She was treated, six hours after ingestion, with oral NAC for 3 days without any side effects.


Introduction
Paracetamol is the most widely used over-the-counter analgesic agent in the world. Its availability (low coast, delivered without medical prescription...) make it the most widely drug involved in accidental paediatric exposures and deliberate self-poisoning cases.
Poison control and pharmacovigilance center in Morocco has listed about 498 paracetamol poisoning between 1980 and 2008 [1]. Used in self-poisoning or after repeated supratherapeutic ingestion, paracetamol overdose can have severe consequences (fulminant liver failure...).

Patient and observation
A 24-year-old Arab female with a body weight of 60 kg, was brought to the emergency department (ED) after she deliberately ingested 100 tablets of 500 mg paracetamol each (50g). She swallowed the tablets at about 4 hours before over 15 minutes that same day. The reason behind her intentional overdose was reported as having family problems. She was not previously known to have any psychiatric or organic problems and this was her first episode.
She had nausea and vomiting. In the first examination, she has normal consciousness. There was no evidence of asterixis or icterus.
Her blood pressure was 120/70 mm Hg, heart rate was 75 beats/minute and respiratory rate was 14/minute. The rest of the examination was normal. The patient has received oral NAC in ED about 6 hours after the ingestion, initiated on 140 mg/kg followed by 70mg/kg at 4-hours intervals. Liver and kidney functions were normal. Serum paracetamol level done 18 hours post ingestion was 900 mg/l using spectrophotometric and chromatographic assays. On review the next days, she was not icteric, there was no Kussmaul's respiration and the liver function tests remained normal. However, due to the massive paracetamol ingestion associated with high serum paracetamol levels, oral NAC 70mg/kg every 4-hourly was continued for the next 2 days. Serum paracetamol level has decreased gradually. The patient was discharged well on the fifth day of hospitalisation. Her serial investigations are shown in Table   1.

Consent:
Written informed consent was obtained from the patient for publication of this case report.

Discussion
Paracetamol is the most widely used over-the-counter analgesic agent in the world. It is involved in a large proportion of accidental paediatric exposures and deliberate self-poisoning cases.
Overdosage of paracetamol can occur following an acute overdose, which is defined as an ingestion of a toxic amount of paracetamol occurring within a period of 8 hours or less, or during repeated supratherapeutic overdose. The dosing threshold at which hepatic injury occurs are shown in Table 2 [2]. After ingestion, paracetamol is rapidly absorbed from the small intestine. Peak serum concentrations occur within 1-2 hours for standard tablet or capsule formulations and within 30 minutes for liquid preparations [3]. Peak should be administered to all patients judged to be at risk of developing hepatotoxicity after paracetamol overdose. With Nacetylcysteine therapy, morbidity from overdose can be minimized [5]. Both intravenous and oral formulations are available (Table 3)  (Table   4). She was treated, six hours after ingestion, with oral NAC for 3 days without any side effects.

Competing interests
The authors declare no competing interests.

Authors' contributions
SB, NH, AB, BB, HS and NK: involvement in the management of the case in critical care unit, preparation and correction of the manuscript. II and SA carried out the toxicological studies. The authors read and approved the final manuscript.

Acknowledgements
We thank Dr M. Benmakhlouf for her assistance in drafting the manuscript. Table 1: Serial laboratory investigations in our patient