A pharmacologic response results when the drug concentration at the site of action reaches or exceeds the minimum effective concentration (MEC). The suggested dosing regimen, including starting dose, maintenance dose, dosage form, and dosing interval, is determined in clinical trials to provide the drug concentrations that are therapeutically effective in most patients. This sequence of events is profoundly affected—in fact, sometimes orchestrated—by the design of the dosage form and the physicochemical properties of the drug. Historically, pharmaceutical scientists have evaluated the relative drug availability to the body in vivo after giving a drug product by different routes to an animal or human, and then comparing specific pharmacologic, clinical, or possible toxic responses.