Which organ is primarily responsible for metabolizing medications?

The liver is primarily responsible for metabolizing medications due to its unique biochemical functions. It contains a variety of enzymes, particularly the cytochrome P450 enzyme system, that play a crucial role in the biotransformation of drugs. This process helps to convert lipophilic compounds into more hydrophilic substances, facilitating their elimination from the body.

The liver's extensive blood supply, receiving blood directly from the digestive tract via the portal vein, allows it to efficiently process and metabolize substances that have been absorbed from the gastrointestinal system. This capability is essential for managing the pharmacokinetics of various medications, affecting both their efficacy and toxicity.

In contrast, while the kidneys are involved in the excretion of metabolites, they do not significantly participate in medication metabolism. The heart and lungs primarily function in circulation and respiration, respectively, and do not directly engage in the metabolic processes for drugs. Thus, the liver stands out as the central organ in drug metabolism, making it the correct answer.