PII‐82

BACKGROUND In swine therapeutics, antibiotics are distributed mostly through feed offered for ad libitum consumption. Our goal is to quantify the impact of individual feed intake of swine on antibiotics exposure. METHODS We develop a computerized ad libitum individual feed intake model that considers the two reported scenarios. To assess the exposure variations of in‐feed chlortetracycline (CTC), we include this model as input function into a pharmacokinetic (PK) model. The model is validated with three data sets collected in a research pigsty. Each set has 36 pigs randomly split in three pens by a weight stratification receiving 0, 500 or 1000 ppm of CTC for 11 days. An electronic feeder records the individual feed intake data. Blood and fecal samples are also taken. RESULTS Our analysis shows that each feeding strategy influences the mean or the fluctuations in CTC plasma concentrations. Exposure to CTC decreases with growth stage and therapy duration. Hence, dosing regimens should be devised based on the MIC of the targeted pathogen, the animal's growth stage and adjusted depending on dosing duration. CONCLUSIONS Our model will assist veterinarians in the design of in‐feed dosing regimens, contribute to the health and welfare of animals and reduce the costs of experiments. This method can be generalized and incorporated into medical practice, particularly to make projections of patient non‐adherence to drugs, to explain treatment failure and to guide practitioners in adjusting the dosing regimen. Clinical Pharmacology & Therapeutics (2005) 79 , P57–P57; doi: 10.1016/j.clpt.2005.12.207