Which of the following is a pro-drug: September 2005
**Core Concept**
A pro-drug is a pharmacologically inactive compound that undergoes metabolic conversion to an active drug within the body. This conversion can occur through various enzymatic reactions, and the resulting active compound is responsible for the therapeutic effect.
**Why the Correct Answer is Right**
The correct answer is a pro-drug because it is a precursor molecule that requires metabolic activation to exert its pharmacological effect. In this case, the pro-drug is converted by an enzyme in the body to an active metabolite, which then binds to its target receptor to produce a therapeutic response. This process involves the action of specific enzymes, such as esterases or amidases, which hydrolyze the pro-drug to release the active compound.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a naturally occurring compound that does not require metabolic activation to exert its effects.
**Option B:** This option is incorrect because it is a drug that is active in its administered form and does not require conversion to exert its pharmacological effects.
**Option C:** This option is incorrect because it is a compound that is toxic or inactive in its administered form and does not undergo metabolic activation to produce a therapeutic effect.
**Clinical Pearl / High-Yield Fact**
It is essential to note that pro-drugs can provide a therapeutic advantage by improving bioavailability, reducing toxicity, or enhancing selectivity. For example, aspirin is a pro-drug that is converted to salicylic acid in the body, which is responsible for its analgesic and anti-inflammatory effects.
**Correct Answer: C. Aspirin is a prodrug that is converted to salicylic acid in the body.