A retrospective evaluation of supratherapeutic dosing of paracetamol among hospitalised adult patients
Authors: Thornton N , McGrogan A , Bastian L , Wilcock M 
Published: November 2024

Introduction

Paracetamol has a maximum daily dose of 4g/24 hours, with a lower maximum dose (60mg/kg/day) for those weighing under 50kg. Various studies have reported on the extent of supratherapeutic dosing in hospital inpatients.1,2,3 Furthermore, there have been a number of datix incidents of supratherapeutic dosing of paracetamol in our hospital. We investigated how often adult patients are administered too high a daily dose.

Aim

To ascertain the extent of greater than maximum administration (4g/24 hours) paracetamol for adult inpatients and where the patient’s weight has been recorded, to report on excessive administration for low body weight patients (less than 50kg).

Method

A retrospective analysis of inpatients 18 years and older administered paracetamol from August 1st 2022 to July 31st 2023. The download from the e-prescribing system (EPS) included various patient characteristics. This dataset was subsequently cleaned and duplicates identified. Microsoft Access was used to run queries to produce a working dataset. As this project falls under the definition of service evaluation, according to UK NHS Research Ethics Committees, formal ethical approval was not required. This project was registered on the hospital’s clinical audit database.

Results

30,716 adults (mean age 59, 41% male) received one or more doses during their stay and 10.2% of these received a supratherapeutic daily dose. Females received 61.2% of the supratherapeutic doses, with 1,909 (10.6%) of 18,088 females receiving doses higher than should have been administered.

Of the 30,716 adult patients, 1108 of them weighed less than 50kg and 420 (37.9%) of these received a supratherapeutic dose (based on their weight) on one or more days.

Of the total 383,222 doses recorded, 82,327 (21.5%) doses were recorded and administered under “as required” (PRN) doses, and 78.5% (n=300,895) as scheduled doses. 2446 (10.4%) of 23,459 adults who received ≥1 scheduled doses had an unintentional overdose on one or more days, with 26,714 total overdoses recorded. 315 (2.2%) of 14,159 adults who received one or more doses PRN, received 1,873 total overdoses.

Discussion / Conclusion

Overall we found 10.2% of adult patients received a daily dose over their patient-specific maximum dose, on at least 1 day. Older studies report slightly lower proportions (6.01%, 6.6%)1,2 than a more recent study (at 17.4%).3 A greater proportion of relative overdosing based on weight, as we found, has been reported elsewhere.3 We also observed that scheduled doses were nearly five times more likely to be the final dose of a supratherapeutic dose on at least one day, and scheduled doses appeared to be present nearly twice as often as PRN when a patient received one or more supratherapeutic dose. It is unclear why such a discrepancy occurred.

Our EPS database enabled more extensive data collection than some other published reports, however limitations include possibly counting overdoses not clinically relevant e.g. fifth dose scheduled for hour 25 but given at hour 24. We did not include paracetamol combination products in our analysis.

These results will be shared with nursing staff and consideration will be given to any possible alert for our EPS.

References

1. Niedrig DF, Bucklar G, Fetzer M, Mächler S, Gött C, Russmann S. Paracetamol overdosing in a tertiary care hospital: implementation and outcome analysis of a preventive alert programme. J Clin Pharm Ther 2016;41:515-518.

2. Zhou L, Maviglia SM, Mahoney LM, Chang F, Orav EJ, Plasek J, et al. Supratherapeutic dosing of acetaminophen among hospitalized patients. Arch Intern Med 2012;172(22):1721-8.

3. Cabrera-Diaz F, Zaugg C, Lim S, Blum K, Salili AR. Implementation and outcome of an electronic tool for detection of paracetamol overdose in a tertiary care hospital. Int J Clin Pharm 2021;43:681–688.