Authors (including presenting author) :
FAN SYC(1), LIU HKA(1), CHAN NYJ(1), CHEN J(3), TAM KYS(3), KWOK HA(1), LAU YFE(2)
Affiliation :
(1) Pharmacy Department, Pamela Youde Nethersole Eastern Hospital
(2) Department of Medicine, Pamela Youde Nethersole Eastern Hospital
(3) Pharmacy Department, Ruttonjee & Tang Shiu Kin Hospitals
Keyword 3: :
Adjusted Body Weight
Keyword 4: :
Ideal Body Weight
Keyword 5: :
Immunoglobulin
Keyword 6: :
Precision Dosing
Introduction :
Intravenous immunoglobulin (IVIG) exhibits a low volume of distribution, primarily confined to the plasma and intravascular space, with minimal distribution into adipose tissue. This pharmacokinetic profile suggests that dosing based on actual body weight (ABW) in obese patients may lead to significant overdosing. With an obesity prevalence of 32.6% in Hong Kong Chinese aged 15-84 with BMI >/=25kg/m2, a precision-dosing strategy is imperative to improve cost-effectiveness.
Objectives :
This study evaluates the implementation of Ideal Body Weight (IBW) or Adjusted Body Weight (AdjBW) for IVIG dosing in Hong Kong East Cluster (HKEC) of the Hospital Authority.
Methodology :
A quality improvement initiative was piloted in HKEC starting in April 2025. The intervention involved multifaceted educational outreach to major IVIG prescribers, i.e., haematologists and neurologists, promoting the adoption of IBW (Devine formula) or AdjBW (AdjBW = IBW + 0.4 × (ABW - IBW)) for all patients with IBW or AdjBW lower than ABW. Support tools, including a handy dosing chart and a dosing calculator, were developed to facilitate prescribing. Adherence was monitored through case reviews and regular feedback to physicians. An interim analysis compared IVIG consumption and expenditure for April-September 2025 against the same period in 2024 within HKEC. IVIG prescriptions were sample reviewed between August – September 2025.
Result & Outcome :
The intervention led to a 7% reduction in IVIG expenditure, from HK$8.4 million (Apr-Sept 2024) to HK$7.7 million (Apr-Sept 2025), saving HK$0.6 million within HKEC. Among seventy-five patient-episodes being dispensed with IVIG between August – September 2025, fifty-one patient-episodes were reviewed. Four patients had no body weight documented and were excluded from the prescription review. Eleven patients were appropriately adopted either IBW or AdjBW as the dosing weight, leading to a total cost reduction of $0.32 million and an extrapolated annual saving of $1.92 million. Thirty-three patients appropriately used ABW for IVIG dosing. The remaining three overweight or obese patients utilised ABW for IVIG dosing. Conclusion: The initial success in the implementation of the precision-dosing strategy for IVIG in the HKEC is encouraging in enhancing medication use within the hospital. The strategy, which aligns with the drug's pharmacokinetics, has resulted in substantial cost savings and reduced the potential risks of fluid overload and thrombosis associated with overdosing. Continuous monitoring and further adoption across other hospitals will further solidify the gains over time.
