Dogs and humans exhibit differences in gastrointestinal physiology. The development of pharmaceuticals for both humans and dogs typically depends upon pharmacokinetic studies in the other species. Product design and quality attributes for dogs (and for humans)generally conduct such extrapolations in a simplistic fashion, without a systematic account of the differential intestinal physiology between dog and human. This project aims to elucidate product quality differences between human and dog oral solid dosage forms as a result of the differential physiology between the two specifies. This insight will facilitate the regulation of canine medicines by highlighting how product standards for human medicines are either too liberal or too restrictive for canine medicines.

Ciprofloxacin hydrochloride will be used as a model poorly soluble drug. A range of immediate-release (IR) tablets will be formulated to map the design space. Formulations will be fast, medium, and slow, with respect to dissolution rate of drug. Ciprofloxacin is expected to exhibit formulation-dependent pharmacokinetics, which is additionally impacted by the differential physiology between dog and humans. In particular, the investigators anticipate a greater sensitivity to formulation for dogs than for humans. Consequently, the investigators anticipate dogs to be more sensitive to formulations, where such critical formulation factors must be considered in canine product design and regulation.

Objectives: 1) The primary objective of this human study is to assess whether specific formulation factors impact the rate and extent of ciprofloxacin oral absorption, as well as the absolute absorption profile of ciprofloxacin. 2) The secondary objective is to assess if dogs exhibit a greater sensitivity to formulation than do humans.

Hypotheses: The investigators anticipate that humans exhibit a modest sensitivity to specific tablet formulation factors. 1) Hence, the hypothesis of this human study is that humans do not exhibit a sensitivity to specific formulation factors and show no in vitro - in vivo correlation to dissolution rate. 2) Alternative hypothesis is that humans do exhibit a sensitivity to specific formulation factors and show an in vitro - in vivo correlation to dissolution rate.