A 60-year-old client is receiving IV gentamicin 1.7 mg/kg every 8 hours for gram-negative sepsis with traditional dosing. The provider orders peak and trough levels around the fourth dose. When does the nurse plan to draw the specimens?

Aminoglycosides (gentamicin, tobramycin, amikacin, streptomycin) are concentration-dependent bactericidal antibiotics with narrow therapeutic windows requiring drug level monitoring. Two dosing strategies: (1) traditional multiple daily dosing — typical 1 to 2 mg/kg every 8 hours; trough drawn 30 minutes before the next scheduled dose; peak drawn 30 minutes after a 30-minute IV infusion ends (or 60 minutes after IM); steady state at the third or fourth dose; goal peak depends on indication (5 to 10 mg/L for systemic gram-negative; up to 8 to 10 for serious infections), trough less than 2 mg/L to limit toxicity; (2) extended-interval (once-daily, "high-dose pulse") — typical 5 to 7 mg/kg every 24 hours, monitored using a single drug level 6 to 14 hours post-dose plotted on a nomogram (Hartford), or random level 8 to 12 hours after dose to confirm clearance, with goal undetectable trough at 24 hours; this strategy maximizes concentration-dependent killing and post-antibiotic effect while limiting nephrotoxicity and ototoxicity. Both strategies require renal function monitoring (creatinine, urine output) and ototoxicity surveillance (hearing changes, tinnitus, vertigo). Drawing both at midway, both before the dose, or no levels at all are unsafe because of the narrow therapeutic window.

Trough = 30 minutes before next dose, peak = 30 minutes after IV infusion ends. Goal trough