Tachyphylaxis is an adverse effect of
**Core Concept**
Tachyphylaxis refers to the rapid decrease in the response to a drug after its initial administration, often due to receptor desensitization or receptor downregulation. This phenomenon is commonly observed with agonist drugs that stimulate receptors, leading to a decrease in the receptor's sensitivity or number over time.
**Why the Correct Answer is Right**
The correct answer is likely related to the mechanism of tachyphylaxis, which involves the desensitization of receptors. For example, in the case of epinephrine, tachyphylaxis occurs due to the rapid downregulation of beta-adrenergic receptors, leading to a decrease in the drug's efficacy. This is a result of the receptor's internalization and subsequent degradation, making it unavailable for subsequent binding.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because while it may be a drug with a rapid onset of action, it is not typically associated with tachyphylaxis.
**Option B:** This is incorrect because it is actually a drug that is used to treat tachyphylaxis, rather than being a cause of it.
**Option C:** This is incorrect because while it may have some adverse effects, tachyphylaxis is not a well-documented side effect of this drug.
**Clinical Pearl / High-Yield Fact**
Tachyphylaxis is often seen with drugs that have a high affinity for their receptors, leading to rapid receptor desensitization. This can be a significant issue in clinical practice, particularly with medications used to treat acute conditions, where a rapid response is critical.
**Correct Answer:** A. Epinephrine