**Question:** A 50 years old male with type 2 diabetes mellitus is found to have 24-hour urinary albumin of 250 mg. Which of the following drugs may be used to retard the progression of the renal disease?

A. ACE inhibitor
B. Angiotensin II receptor blocker
C. Thiazide diuretic
D. Glucosylated hemoglobin lowering agent

**Core Concept:**
In patients with type 2 diabetes mellitus and diabetic nephropathy, retarding the progression of renal disease is crucial to prevent end-stage renal disease and its complications. This can be achieved by targeting the renin-angiotensin-aldosterone system (RAAS) blockade, as well as glucose control.

**Why the Correct Answer is Right:**
The correct answer, B. Angiotensin II receptor blocker (ARB), belongs to the class of drugs known as Renin-Angiotensin-Aldosterone System (RAAS) inhibitors. RAAS inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and ARBs, are essential drugs in the management of diabetic nephropathy. By blocking the Angiotensin II, they help in reducing albuminuria and slowing down the progression of renal disease.

**Why Each Wrong Option is Incorrect:**

A. ACE inhibitor (Option A) is another RAAS inhibitor, but it is not the correct answer because it is a first-generation RAAS inhibitor, while the correct answer is an ARB, a more recent and potent RAAS inhibitor.

B. Thiazide diuretic (Option C) is a diuretic that primarily lowers blood pressure and reduces extracellular volume expansion. Although it can lower blood pressure, it does not specifically target the RAAS system, unlike ACE inhibitors and ARBs. Therefore, its effectiveness in reducing albuminuria and slowing down the progression of renal disease is less than that of ACE inhibitors and ARBs.

D. Glucose lowering agents (Option D) primarily focus on blood glucose control, which is essential for diabetic patients but are not directly involved in the reduction of albuminuria and slowing down the progression of renal disease.

**Clinical Pearl:**
In diabetic nephropathy, the renin-angiotensin-aldosterone system (RAAS) inhibitors are the cornerstone of management to reduce albuminuria and slow down the progression of renal disease. ACE inhibitors and ARBs (Option B) are both effective, but ARBs are a more potent, selective, and better tolerated option, making it the preferred choice.