Aim In England, 17% of children aged 2–15 are considered obese and a further 13% overweight.1 Physiological changes associated with obesity affect pharmacokinetic and pharmacodynamic parameters which may necessitate paediatric drug dose alteration although few guidelines exist to support this in clinical practice. This study aimed to:
determine the proportion of patients at a large paediatric hospital prescribed analgesics postoperatively who are obese or overweight
evaluate how analgesics are currently prescribed for these overweight and obese patients
determine whether doses are altered according to published recommendations
determine whether clinical outcomes differ for overweight or obese children compared to non-overweight children
Method Postoperative paediatric inpatients aged 2–15 prescribed paracetamol, ibuprofen or morphine (or combination thereof) were included in the six-week prospective study. Demographic (age, weight, height, gender), prescription (drug name, dose, route, frequency) and clinical (surgical specialty, pain scores, paediatric early warning scores) information was collected from medical notes and drug charts. Patients with significant organ impairment or requiring intensive care were excluded.
Body-mass-index centile (BMI-C) was calculated for each child using a validated web-based calculator and used to classify patients as non-overweight (BMI-C <91), overweight (BMI-C ≥91 and <98) or obese (BMI-C ≥98). Prescribed paracetamol and morphine doses were evaluated against patients’ total body weight (TBW) and ideal body weight (IBW) and ibuprofen doses were evaluated against patients’ TBW and lean body mass (LBM)2 according to published dosing adjustment recommendations2 3 and compared against formulary dosing standards.4 Clinical outcome data was used to evaluate pain control and clinical status.
Results BMI-C was calculated for 198 postoperative paediatric inpatients, and of these 142 (72%) were non-overweight, 27 (13.5%) were overweight and 29 (14.5%) were obese. Complete prescription and clinical data were available for 44 non-overweight, 22 overweight and 23 obese patients who were subjected to further analysis. Formulary dosing standards were 15 mg/kg for paracetamol, 5 mg/kg for ibuprofen and 0.1–0.2 mg/kg for morphine. Mean postoperative oral paracetamol doses were 15.0 mg/TBW, 18.1 mg/IBW and 20.6 mg/IBW for non-overweight (n=43), overweight (n=22) and obese (n=23) patients respectively. Mean postoperative oral ibuprofen doses were 5.0 mg/TBW, 5.7 mg/LBM and 6.2 mg/LBM for non-overweight (n=37), overweight (n=16) and obese (n=21) patients respectively. Mean postoperative oral morphine doses were 0.14 mg/TBW, 0.17 mg/IBW and 0.18 mg/IBW for non-overweight (n=33), overweight (n=13) and obese (n=16) patients respectively. There was no significant difference in pain scores or paediatric early warning scores at 0-, 4- 12- and 24-hours post-surgery between the three cohorts.
Conclusion The proportion of patients in this study who were overweight or obese aligned with national prevalence data. Children who were overweight or obese received higher doses of paracetamol, ibuprofen and morphine compared to non-overweight children, and doses of paracetamol and ibuprofen were greater than formulary dosing standards. This suggests that doses for obese or overweight children are not adequately adjusted according to IBW or LBM which may result in drug toxicity. Guidance for prescribers is need to aid identification of patients who are overweight or obese and to guide appropriate dose adjustment.
NatCen Social Research. Health Survey for England 2017: Adult and child overweight and obesity. National Statistics & NHS Digital. https://files.digital.nhs.uk/3F/6971DC/HSE17-Adult-Child-BMI-rep.pdf [accessed 4 April 2019]
UK Medicines Information & Neonatal and Paediatric Pharmacists Group. How should medicines be dosed in children who are obese? 2018 https://www.sps.nhs.uk/articles/how-should-medicines-be-dosed-in-children-who-are-obese/ [accessed 20 December 2018]
Sydney Children’s Hospital. Drug Dosing for Overweight and Obese Patients. 2013. http://www.schn.health.nsw.gov.au/_policies/pdf/2013-7034.pdf [accessed 15 November 2018]
Evelina London Children’s Hospital. Paediatric Formulary. http://cms.ubqo.com/public/d2595446-ce3c-47ff-9dcc-63167d9f4b80 [accessed 26 December 2018].
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