Which factors can affect drug absorption?

Drug absorption is a complex process influenced by various physiological and formulation-related factors, making the choice indicating "all of the above" the most accurate.

The formulation and route of administration significantly influence how a drug is absorbed. For instance, oral, intravenous, intramuscular, and subcutaneous routes each have different absorption characteristics. Tablets, capsules, and liquid forms of medication can have varied bioavailability depending on their formulation—some may dissolve quickly and be absorbed more readily, while others may take longer.

Blood flow to the absorption site also plays a crucial role; enhanced blood flow can increase the rate of absorption. For instance, drug absorption is generally faster in areas with rich blood supply compared to those with less blood flow. Further, the presence of food in the gastrointestinal tract can alter the absorption of many medications. Food can enhance absorption for certain drugs but may hinder the effectiveness of others by altering gastric pH or slowing gastric emptying.

While formulation and age does impact absorption—such as differences in gastric pH and motility in younger versus older patients—the comprehensive nature of other factors makes the choice reflecting "all of the above" the most representative of the complexities involved in drug absorption. Thus, every factor listed contributes independently and interactively to the overall