What factor is NOT influential in drug absorption?

The absorption of drugs into the body is influenced by several critical factors, and among those is the pH of the drug, its solubility, and the blood supply to the absorption area. The pH can affect the ionization of the drug, which in turn influences its ability to traverse cell membranes. The solubility of the drug is crucial because only soluble drugs can be absorbed effectively in the gastrointestinal tract or other relevant areas of absorption. Blood supply is equally important; well-perfused areas will facilitate quicker and more efficient absorption of drugs into the systemic circulation.

In contrast, while an animal's breed may have implications for drug metabolism and pharmacodynamics, it does not directly influence the fundamental process of drug absorption. Factors such as size, body composition, and metabolic rate could vary between breeds, but these do not alter the fundamental characteristics of the drug itself or its absorption mechanism. Thus, breed is not a determining factor in how a drug is absorbed.