Which action involves the movement of drugs through biological membranes?

The action that involves the movement of drugs through biological membranes is absorption. Absorption is the process by which a drug is taken into the body and enters the bloodstream after being administered. This movement typically occurs across cellular membranes in the gastrointestinal tract, skin, or other tissues, depending on the route of administration.

Factors influencing absorption include the drug's formulation, the presence of food in the stomach, blood flow to the absorption site, and the overall health of the individual. Once the drug is absorbed into the bloodstream, it can then be distributed to various tissues and organs where it exerts its therapeutic effects.

The other options relate to different phases of drug handling in the body. Excretion refers to the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys or liver. Biotransformation involves the chemical modification made by an organism on a chemical compound, which commonly occurs in the liver and affects the drug's efficacy and toxicity. Distribution, on the other hand, encompasses the dispersion of the drug throughout the body's fluids and tissues after absorption has occurred.