INTRODUCTION:

Obesity alters the pharmacokinetic (PK) properties of drugs making it difficult to determine the appropriate dose when administering weight-based medications. Alternative descriptors of body weight, such as lean body mass (LBM) and ideal body weight (IBW), are sometimes used in these situations.

METHODS:

We performed a single-centre, randomized, controlled, open-label, 3 × 3 crossover trial to determine whether recombinant factor VIII (rFVIII) dosing based on LBM and IBW achieves a targeted FVIII recovery with better precision than based on total body weight (TBW) in overweight and obese, adult males with haemophilia A. Participants were randomized to 1 of 6 possible FVIII concentrate dosing sequence scenarios (TBW, LBM and IBW). Recombinant FVIII was administered on 3 separate weeks following a washout period of at least 72 hours.

RESULTS:

A total of 19 participants were randomized and completed the study. FVIII recovery was lower at 30 minutes post-rFVIII infusion in LBM vs TBW and IBW vs TBW-based dosing, mean difference -0.38 (95% CI: -0.56, -0.20) and -0.28 (95% CI: -0.47, -0.10) IU/dL per IU/kg, respectively. In LBM vs TBW and IBW vs TBW-based dosing, there was a non-significant increase in the proportion of participants with a targeted FVIII recovery of 2.00 ± 0.20 IU/dl per IU/kg, OR = 1.93 (95% CI: 0.44, 8.55) and OR = 3.65 (0.80, 16.72), respectively.

DISCUSSION:

Based on our study's findings, overweight and obese patients with haemophilia A may benefit from an individualized PK analysis using LBM and IBW to determine the most accurate, and potentially cost-effective, method of achieving targeted FVIII recovery.