MFMSO201207e03


 

Longo, C.  (2012). The Role of Excess Weight in Antibiotic Treatment Failure. McGill Family Medicine Studies Online, 07: e03.    Archived by WebCite®   

at  http://www.webcitation.org/66I1cofK6

 

 

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Abstract

 

Objectives: To determine whether excess weight is associated with antibiotic
treatment failure (ATF) and if this may be due to a lack of weight-based dosing.

Methods: Using a historical cohort study design, data linked to Quebec
administrative databases were available for 18 014 consenting patients randomly
sampled from the 1992 and 1998 Santé Québec Health surveys (response rate
85%). Selected patients were within the normal weight, overweight and obese
weight classes aged 20–79 years, receiving at least one episode of antibiotic
therapy from the health survey date to December 2005. ATF was measured via
secondary antibiotic prescriptions or additional hospitalizations for infections
within the month following initial therapy for each participant. The antibiotic
daily dose (DD) and daily dose to body mass index (DD:BMI) ratios were
computed for those receiving an oral antibiotic prescription. Logistic regression
was performed to determine whether overweight and/or obesity as well as dosing
factors (e.g. DD:BMI) were significant predictors of ATF, while one-way
ANOVA with Tukey-Kramer adjustment for multiple comparisons was used to
determine if DD:BMI ratios differed significantly across weight groups, reflecting
a lack of weight-based dosing.

Results: Of the 6 179 patients selected, 828 (13.4%) had an ATF event during the
outcome assessment period. Obesity was found to be a significant predictor of
ATF with an OR of 1.26 (95% CI 1.03-1.52), after adjusting for other potential
confounders including sociodemographic, and antibiotic-related factors (e.g.
MRSA and history of antibiotic use). The antibiotic DD:BMI ratio means differed
significantly between weight groups, where means decreased with increasing
BMI. When included in the ATF predictive model along with other previous
confounding factors, the DD:BMI variable was significant (p-value of 0.03) with
a modest adjusted OR of 1.004 (95% CI 1.000-1.007).

Conclusions: Obesity is a significant predictor of ATF and this association is
likely due to the current “one size fits all” dosing strategy. Findings may
encourage further research in the field of pharmacokinetics and family medicine
to find a means of standardizing current antibiotic dosing guidelines for weight as
well as implementing weight-based dosing in family practice.