**Core Concept**
Pseudoephedrine is a non-selective alpha-adrenergic receptor agonist that acts as a nasal decongestant by causing vasoconstriction of the nasal blood vessels. Its use requires caution in conditions that may be exacerbated by increased sympathetic activity or affected by the drug's vasoconstrictive effects.

**Why the Correct Answer is Right**
Pseudoephedrine should be used cautiously in patients with conditions that may be worsened by increased heart rate, blood pressure, or cardiac workload. This includes patients with **hypertension**, **coronary artery disease**, and **thyrotoxicosis**. In these conditions, the sympathomimetic effects of pseudoephedrine can lead to further increases in heart rate and blood pressure, potentially causing adverse outcomes.

**Why Each Wrong Option is Incorrect**
**Option A:** **Hypertension** - Pseudoephedrine can increase blood pressure and worsen hypertension, making it a condition that requires cautious use of the drug.
**Option B:** **Coronary artery disease** - Pseudoephedrine can increase cardiac workload and oxygen demand, potentially leading to myocardial ischemia in patients with coronary artery disease.
**Option C:** **Thyrotoxicosis** - Pseudoephedrine can exacerbate the sympathetic effects of thyrotoxicosis, leading to further increases in heart rate and cardiac workload.

**Clinical Pearl / High-Yield Fact**
When using nasal decongestants like pseudoephedrine, it's essential to carefully evaluate the patient's cardiovascular status and use the drug cautiously in conditions that may be worsened by increased sympathetic activity.

**Correct Answer:** D