Which two analgesics listed do not require therapeutic drug monitoring?

• A. Acetylsalicylate (Aspirin) and Acetaminophen (Tylenol)
• B. Ibuprofen and Naproxen
• C. Codeine and Morphine
• D. Diclofenac and Indomethacin

Answer: (A)

Therapeutic drug monitoring is used when a drug has a narrow therapeutic index or unpredictable pharmacokinetics, so levels in the blood help tailor dosing and avoid toxicity. For common analgesics, routine monitoring of blood levels isn’t typically required.

Aspirin (acetylsalicylate) and acetaminophen are given within well-established dosing ranges, and in everyday use their levels don’t guide therapy. Blood levels are mainly reserved for specific situations: aspirin in suspected salicylate toxicity or overdose, and acetaminophen when overdose or risk of liver injury is present, where levels help guide treatment decisions (like overdose management with antidotes). In routine pain management, you rely on dose, response, and safety monitoring rather than measuring drug concentrations.

Other listed analgesics don’t routinely require blood-level monitoring either in standard practice; their use focuses on dosing, efficacy, and monitoring for adverse effects. Drug levels might be checked in particular circumstances (overdose, toxicity, or highly variable metabolism), but that’s not part of routine therapeutic monitoring.