Information provision for antibacterial dosing in the obese patient: a sizeable absence?

Background: Obesity is on course to overtake being underweight as a global disease burden. Obesity alters antibacterial pharmacokinetics (PK) and pharmacodynamics (PD). Historically, drug PK/PD parameters have not been studied in obese populations. This means dose recommendations risk being sub-therapeutic in a population at increased risk of infection. Suboptimal antibacterial prescribing is widely associated with treatment failure, worse clinical outcomes, unnecessary escalation to broad-spectrum therapy and the emergence of antimicrobial resistance (AMR).

Objectives: To analyse current information provided by pharmaceutical companies, for the most commonly prescribed antibacterial agents in the UK, for evidence of dosing guidance for obese adults.

Methods: We analysed the manufacturers' Summary of Product Characteristics (SPC) for 42 of the most clinically important and frequently prescribed antibacterial agents dispensed across both primary and secondary care. The manufacturer's SPC was reviewed, and cross-referenced with the online British National Formulary, to assess dosing guidance for obese adults.

Results: No advice was provided to guide dosing for obese adults in 35 (83%) of 42 of the most clinically important and frequently prescribed antibacterial agents in the UK. Seven (17%) antibacterial agents (tigecycline, vancomycin, daptomycin, amikacin, gentamicin, tobramycin and teicoplanin) provided variable levels of advice.

Conclusions: There is a paucity of advice and evidence in the UK to guide dosing common antibacterial agents in the obese. The literature on antibacterial PK/PD studies in obese populations remains scarce. In the face of the increasing risks of AMR combined with the global rise of obesity there is an urgent need to address this significant research gap.