**Question:** Therapeutic monitoring of plasma level of drug is done when using all of the following drugs except

A. ACE inhibitors (angiotensin-converting enzyme inhibitors)
B. Angiotensin II receptor blockers (ARBs)
C. Calcium channel blockers
D. Beta-blockers

**Correct Answer:** .

**Core Concept:**
Therapeutic drug monitoring (TDM) is a process used in clinical practice to optimize the dosage of a medication to achieve the desired therapeutic effect and minimize adverse reactions. By analyzing the plasma concentration of a drug, healthcare professionals can determine the most appropriate dosage for the individual patient, considering factors such as drug-drug interactions, renal or hepatic impairment, and patient age or body weight.

**Why the Correct Answer is Right:**
Among the provided options, the correct answer is **D. Beta-blockers** because TDM is not typically required for these drugs. Beta-blockers, a class of medications used to treat cardiovascular diseases, work by blocking beta-adrenergic receptors in the heart and blood vessels, ultimately reducing heart rate, blood pressure, and cardiac output. The dose adjustment is typically guided by clinical response and signs of over- or under-medication, rather than relying on plasma drug levels.

**Why Each Wrong Option is Incorrect:**

A. **ACE inhibitors (angiotensin-converting enzyme inhibitors)** are often monitored for therapeutic drug monitoring because they can cause side effects like hyperkalemia, angioedema, or renal impairment. By monitoring the plasma levels of these drugs, healthcare professionals can adjust the dosage accordingly to minimize these adverse reactions and maintain therapeutic efficacy.

B. **Angiotensin II receptor blockers (ARBs)** also require monitoring, particularly in patients with decreased renal function or those receiving concomitant medications that may affect drug clearance, such as NSAIDs or ACE inhibitors. Monitoring helps to maintain the drug's therapeutic range and prevent adverse effects.

C. **Calcium channel blockers** usually do not require therapeutic drug monitoring unless patients are experiencing side effects like bradycardia or hypotension. In these cases, dosage adjustments can be guided by plasma levels.

D. **Beta-blockers** have been discussed above as not typically requiring therapeutic drug monitoring.

**Clinical Pearls:**

1. When prescribing and adjusting drug dosages, consider the patient's clinical response, potential side effects, and the drug's pharmacokinetic properties (i.e., absorption, distribution, biotransformation, and excretion).
2. Monitoring is essential for drugs that can cause severe side effects or interact with other medications, like ACE inhibitors, ARBs, and calcium channel blockers.
3. Monitoring is also useful for drugs like ACE inhibitors and ARBs in patients with decreased renal function or those receiving concomitant medications that may affect drug clearance.
4. In some cases, monitoring can guide dosage adjustments for medications like calcium channel blockers, beta-blockers, and ACE inhibitors to prevent adverse effects.