**Question:** All of the following drugs are administered orally except:

A. Insulin
B. Heparin
C. Nitroglycerin
D. Corticosteroids

**Core Concept:** Different drug classes and their modes of administration, with emphasis on oral dosage forms.

**Why the Correct Answer is Right:** Insulin is a peptide hormone used to regulate blood glucose levels in diabetics. It is administered via injection, typically subcutaneous, as it is not stable when taken orally. Heparin is a potent anticoagulant that works by inhibiting factor Xa and is commonly administered via intravenous infusion or subcutaneous injection as oral administration would render its therapeutic effect ineffective due to its rapid degradation in the gastrointestinal tract.

**Why Each Wrong Option is Incorrect:**

- Nitroglycerin is a vasodilator used for angina and hypertension. It is also not suitable for oral administration, as it is a highly unstable, odorous, and sensitive to light substance. Its primary mode of administration is transdermal or sublingual.
- Corticosteroids are a class of steroid hormones with anti-inflammatory, immunosuppressive, and anti-allergic effects. They can be administered orally, topically, or parenterally (intravenous, intramuscular, or subcutaneous injections). Thus, option B (Heparin) and D (Corticosteroids) are correct, while A (Insulin) and C (Nitroglycerin) are incorrect.

**Clinical Pearl:** When assessing patient compliance and dosage administration methods, it is essential to consider drug stability, pharmacokinetic properties, and the intended therapeutic effect of each medication. This knowledge helps ensure safe and effective drug therapies for patients.