Final answer:
Drugs are eliminated from the body as both metabolites, often resulting from oxidation reactions, and as unchanged substances, either through urinary excretion or other elimination pathways.
Step-by-step explanation:
The drugs are eliminated as both metabolites and unchanged. In the body, foreign substances such as drugs are subject to metabolic processes which are generally grouped into two phases: Phase-I and Phase-II. In Phase-I, oxidation, reduction, and hydrolysis occur, transforming drugs into different substances. For example, alcohols may be oxidized into corresponding acids. In Phase-II, conjugation or synthesis with another substance in the body takes place, preparing the drug for excretion.
Drugs and their metabolites can be eliminated by the urinary system through processes like glomerular filtration, tubular secretion, or tubular reabsorption. While water-soluble drugs may be excreted in the urine, fat-soluble drugs, or those that are unchanged, may require different elimination pathways.
Therefore, the answer to the question is 'c. both (a) and (b)'. Drugs are eliminated as metabolites produced during their oxidation reactions and also as unchanged substances.