Which term describes the movement of the drug from the bloodstream into tissues?

• A. Absorption
• B. Distribution
• C. Metabolism
• D. Excretion

Answer: (B)

Distribution is the movement of a drug from the bloodstream into tissues, shaping how quickly and how much drug reaches various parts of the body, including the brain. After a drug enters circulation, its distribution depends on factors like blood flow to tissues, how easily the drug crosses capillary walls, and its chemical properties (lipid solubility, ionization, and how much is bound to plasma proteins). For oral sedatives, rapid onset often requires the drug to be lipophilic enough to cross cell membranes and, if needed, the blood-brain barrier, so it can exert effects in the central nervous system. Absorption refers to how the drug enters the bloodstream from the administration site, metabolism is the chemical alteration of the drug (often in the liver), and excretion is its elimination from the body. The essence is that distribution describes moving from blood into tissues, not entry into the blood, chemical change, or removal from the body.