A 68-year-old man with chronic kidney disease (eGFR 25 mL/min/1.73m²) and hypertension requires an antihypertensive agent. Which drug would be the LEAST suitable choice due to unfavorable pharmacokinetics in renal impairment?

Explanation

## Pharmacokinetic Considerations in Renal Impairment **Key Point:** Drugs that are renally eliminated or have active metabolites requiring renal clearance must be dose-adjusted or avoided in chronic kidney disease (CKD). ### Drug Elimination Pathways in CKD | Drug | Primary Elimination | Renal Clearance | CKD Suitability | |------|--------------------|-----------------|-----------------| | Amlodipine | Hepatic metabolism | Minimal (~10%) | Safe; no dose adjustment | | Enalapril | Renal (active metabolite) | High | Requires dose adjustment | | Atenolol | Renal excretion | 85–90% unchanged | **CONTRAINDICATED in severe CKD** | | Losartan | Hepatic metabolism | Minimal | Safe; no dose adjustment | **High-Yield:** Atenolol is a **hydrophilic beta-blocker** with 85–90% renal elimination. In severe CKD (eGFR <30), it accumulates to toxic levels, causing profound bradycardia, hypotension, and bronchospasm. Lipophilic beta-blockers (e.g., metoprolol, labetalol) are safer alternatives. ### Why Atenolol is Unsuitable Here 1. **Renal dependence:** ~85–90% excreted unchanged in urine 2. **Accumulation risk:** In eGFR 25, drug half-life extends dramatically, leading to toxicity 3. **No hepatic metabolism:** Cannot bypass renal clearance 4. **Clinical consequence:** Risk of severe bradycardia, AV block, cardiogenic shock **Clinical Pearl:** The rule of thumb — **hydrophilic drugs with >70% renal elimination are contraindicated in eGFR <30**. Atenolol, sotalol, and nadolol fall into this category. ### Safer Alternatives in CKD Stage 4–5 - **Amlodipine:** Hepatically metabolized; no dose adjustment needed - **Losartan:** Hepatic metabolism; safe in renal impairment - **Enalapril:** Requires dose reduction (e.g., 50% at eGFR <30) but still usable - **Labetalol or metoprolol:** Lipophilic beta-blockers; safer than atenolol **Mnemonic:** **HARD drugs in renal failure** = **H**ydrophilic, **A**ctive metabolites, **R**enally dependent, **D**ose-dependent toxicity.