METHODS: Retrospective case review of children <6 years-old with liquid paracetamol overdoses referred to a regional poisons information centre January 2017 to August 2022. We extracted data on the exposure and management from the poisons information centre and hospital medical records. We identified additional cases with two paracetamol concentrations obtained from September 2022 to June 2024.

RESULTS: Of 437 paediatric poisonings, 271 were eligible for inclusion. The median age was 24 months, the median time to presentation was 120 min, and paracetamol was the sole ingestant in 92% of cases. Blood testing was recommended in 131 patients (48.3%), occurring at 2 h post-ingestion in 62 patients (47.3%). Testing at a later time was mostly due to delayed presentation, including to hospitals unable to measure paracetamol concentrations. Eighteen patients (16.7%) had repeat blood testing, and five additional cases were identified in the subsequent period. Overall, the concentration decreased in 19 patients (83%), but in three patients it increased, from 73 mg/L to 81 mg/L (0.49-0.54 mmol/L), from 154 mg/L to 179 mg/L (1.03-1.19 mmol/L), and from 56 mg/L to 115 mg/L (0.37-0.77 mmol/L). Symptomatic patients were more likely to receive a second blood test or acetylcysteine while awaiting investigations. Of 19 patients administered acetylcysteine, it was discontinued in five due to low paracetamol serum concentrations. All patients recovered.

DISCUSSION: Guidelines were followed in >90% of patients and this testing regimen shortened length of stay. Based on these data, Australian treatment guidelines now recommend repeat testing for 2 h paracetamol serum concentrations >100 mg/L (0.67 mmol/L).

METHOD: This is a single-center, single-dose, open-label, randomized, 2-treatment, 2-sequence and 2-period crossover study with a washout period of 7 days. Paracetamol/Orphenadrine tablets were administered after a 10-h fast. Blood samples for pharmacokinetic analysis were collected at scheduled time intervals prior to and up to 72 h after dosing. Blood samples were centrifuged, and separated plasma were kept frozen (- 15 °C to - 25 °C) until analysis. Plasma concentrations of orphenadrine and paracetamol were quantified using liquid-chromatography-tandem mass spectrometer using diphenhydramine as internal standard. The pharmacokinetic parameters AUC0-∞, AUC0-t and Cmax were determined using plasma concentration time profile for both preparations. Bioequivalence was assessed according to the ASEAN guideline acceptance criteria for bioequivalence which is the 90% confidence intervals of AUC0-∞, AUC0-t and Cmax ratio must be within the range of 80.00-125.00%.

RESULTS: There were 28 healthy subjects enrolled, and 27 subjects completed this trial. There were no significant differences observed between the AUC0-∞, AUC0-t and Cmax of both test and reference preparations in fasted condition. The 90% confidence intervals for the ratio of AUC0-t (100.92-111.27%), AUC0-∞ (96.94-108.08%) and Cmax (100.11-112.50%) for orphenadrine (n = 25); and AUC0-t (94.29-101.83%), AUC0-∞ (94.77-101.68%) and Cmax (87.12-101.20%) for paracetamol (n = 27) for test preparation over reference preparation were all within acceptable bioequivalence range of 80.00-125.00%.

CONCLUSION: The test preparation is bioequivalent to the reference preparation and can be used interchangeably.