What is the initial step in the process of drug passage through the body?

The initial step in the process of drug passage through the body is drug absorption. This refers to the process by which a drug is taken up into the bloodstream after administration. Absorption is crucial because it determines how much of the drug will be available to exert its effects once it reaches systemic circulation.

When a drug is administered, it must be absorbed from the site of administration (such as the gastrointestinal tract, muscle, or skin) into the bloodstream. This process can be influenced by various factors, including the drug's formulation, route of administration, and the physiological conditions of the body. Understanding absorption is vital for predicting how effectively a drug will work and for determining the appropriate dosage and route to achieve the desired therapeutic effect.

The other options pertain to processes that occur after absorption. Active transport refers to the mechanism by which substances are moved across cell membranes against their concentration gradient, primarily occurring in the distribution phase. Distribution is the movement of the drug through the bloodstream to various tissues and organs. Excretion is the final step, where the drug is eliminated from the body, typically via urine or feces. Each of these phases is critical, but they follow the initial step of absorption, which sets the stage for how the drug interacts with the body