ABSTRACT
This chapter details the circumstances for exposure and dosage of a drug that favor or deter the potential for clinical toxicity. Oral administration of drugs and toxins is by far the most popular route of exposure. Oral administration involves the presence of several physiological barriers, which must be penetrated or circumvented if an adequate blood concentration of the compound is to be achieved. The mucosal layers of the oral cavity, pharynx, and esophagus consist of stratified squamous epithelium, which serves to protect the upper gastrointestinal lining from the effects of contact with physical and chemical agents. Simple columnar epithelium lines the stomach and intestinal tracts, which function in digestion, secretion, and some absorption. Frequency of administration considers a single or repeated administration of a dose of the drug or toxin during the exposure period. Single-dose exposures are essentially associated with acute duration and are the most frequent and convenient methods of experimental drug administration.
