Which of the following drugs is capable of maintaining blood levels for 24 hours after a single administration but has useful antianginal effects lasting only about 10 hours?
**Core Concept**
The question is testing the pharmacokinetics and pharmacodynamics of antianginal drugs, specifically their duration of action and maintenance of blood levels. The correct answer requires an understanding of the drug's half-life and its therapeutic effects.
**Why the Correct Answer is Right**
The correct answer is a long-acting nitrate, which maintains blood levels for 24 hours after a single administration due to its long half-life. However, its antianginal effects last only about 10 hours because the nitrate is gradually metabolized and excreted, leading to a decrease in its plasma concentration and therapeutic effect. Nitrate-induced vasodilation is a key mechanism in reducing angina symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because nitrates with shorter half-lives, such as isosorbide dinitrate, do not maintain blood levels for 24 hours.
**Option B:** This is incorrect because beta-blockers, such as propranolol, do not have antianginal effects that last only about 10 hours; their effects can last much longer.
**Option C:** This is incorrect because calcium channel blockers, such as verapamil, have a different mechanism of action and duration of action compared to nitrates.
**Clinical Pearl / High-Yield Fact**
Long-acting nitrates can be administered transdermally or orally and provide sustained relief from angina symptoms, but their effects can be unpredictable due to factors such as nitrate tolerance.
**Correct Answer: C. A long-acting nitrate.**