**Question:** The following drug is given in a pulsatile manner?

A. Insulin
B. Thyroxine
C. Epinephrine
D. Heparin

**Core Concept:**
Pulsatile administration refers to the method of drug administration where the drug is given in a manner that mimics the natural physiological rhythm or pattern, typically in relation to hormones or substances with pulsatile release. In this case, pulsatile administration would be expected for drugs that are released periodically or have a cyclical pattern in their therapeutic effect.

**Why the Correct Answer is Right:**
The correct answer is D. Heparin, as heparin is a drug used to prevent blood clots and is released in a pulsatile manner to match the physiologic release pattern of antithrombin III, which is the primary inhibitor of blood coagulation. Heparin is given intermittently to maintain the optimal therapeutic effect, as its continuous administration can lead to bleeding complications due to excessive inhibition of coagulation factors.

**Why Each Wrong Option is Incorrect:**
A. Insulin (Option A) is a hormone used to regulate blood glucose levels in diabetes mellitus. It is typically administered twice daily, regardless of pulsatile administration.
B. Thyroxine (Option B) is a hormone used to treat hypothyroidism. Its administration is usually once daily, not pulsatile.
C. Epinephrine (Option C) is a hormone involved in response to stress or shock. Its pulsatile administration is uncommon and depends on the specific clinical situation.

**Clinical Pearl:**
Understanding pulsatile administration is crucial for effective drug therapy as it helps mimic natural physiological patterns and ensures optimal drug action. However, the answer depends on the specific drug and its intended therapeutic effect. Keep in mind that pulsatile administration is not applicable to all drugs and should be guided by the specific pharmacology and physiology of the drug being administered.