Drug Levels & Therapeutic Monitoring: Timing, Targets, and the Mistakes That Cause Toxicity
Drug Levels & Therapeutic Monitoring: Timing, Targets, and the Mistakes That Cause Toxicity Vancomycin has gone AUC/MIC. Phenytoin needs albumin correction. And lithium levels drawn at the wrong time are useless. NPs in primary care co-manage patients on narrow therapeutic index medications constantly—anticonvulsants, lithium, digoxin, immunosuppressants, and antibiotics. Getting the timing wrong on a drug level makes the result uninterpretable. Getting the target wrong leads to toxicity or treatment failure. Quick-Reference: Key Drugs Drug Therapeutic Range When to Draw Key Pitfall Vancomycin AUC/MIC 400–600 (current standard); trough 15–20 is outdated for serious MRSA but still used in some settings AUC requires 2 levels (1–2 hr post-infusion + trough). For trough-only: draw 30 min before next dose. AUC/MIC monitoring is now the 2020 ASHP/IDSA guideline standard. Trough-only monitoring overexposes patients to nephrotoxicity. Digoxin 0.8–2.0 ng/mL (HF benefit at lower range ...