Which of the following is primarily responsible for the distribution of drugs in the body?

The circulatory system is primarily responsible for the distribution of drugs in the body because it facilitates the transport of medications through blood flow. Once a drug is absorbed into the bloodstream, the circulatory system carries it to various tissues and organs where it exerts its therapeutic effects. The heart pumps blood through arteries and veins, ensuring that medications are delivered efficiently throughout the body. This system plays a crucial role in determining how quickly and effectively a drug reaches its target sites, influencing both the onset and duration of its action.

In contrast, the absorption process refers to how a drug enters the bloodstream, which occurs before distribution. Excretion organs are involved in the elimination of drugs from the body, a process that happens after distribution and metabolism. The nervous system mainly communicates signals throughout the body but does not play a direct role in the transport of drugs. Hence, the circulatory system is the key player in drug distribution, making it the correct answer.