Final answer:
Liver metabolism has the least effect on the absorption of an orally administered drug; it is more involved in the bioavailability and pharmacokinetics post absorption. Other factors like gastric pH, blood flow to the GI tract, and drug formulation are directly involved in the drug's initial absorption.
Step-by-step explanation:
Among the given options relating to factors that can affect an orally administered drug's absorption or distribution, liver metabolism would least affect the drug's absorption since liver metabolism occurs after the drug has been absorbed from the gastrointestinal (GI) tract. Gastric pH, blood flow to the GI tract, and drug formulation are all factors directly involved in the initial absorption process of a drug. In contrast, liver metabolism is a part of the drug's bioavailability and pharmacokinetics after it has entered the systemic circulation. It is important to understand the barriers to drug exposure, such as cell membranes, metabolic enzymes, and plasma protein binding, as well as the most common mechanism for drug absorption, which is passive diffusion.