Aminoglycoside Dosing Reference — Amikacin & Gentamicin
| Drug / Patient | Dose | Interval | TDM peak target | TDM trough limit |
|---|---|---|---|---|
| Amikacin — adult OD | 15–20 mg/kg | Every 24h (adjust CrCl) | 56–64 mg/L | <5 mg/L |
| Amikacin — traditional BD | 7.5 mg/kg | Every 12h | 20–30 mg/L | <10 mg/L |
| Amikacin — child | 15–22 mg/kg/day | Every 24h (OD) | 20–35 mg/L | <5 mg/L |
| Amikacin — neonate term | 15 mg/kg | Every 36h | — | <5 mg/L (trough) |
| Gentamicin — adult OD | 5–7 mg/kg | Every 24h (adjust CrCl) | 15–20 mg/L | <1 mg/L |
| Gentamicin — traditional TDS | 1–1.7 mg/kg | Every 8h | 5–10 mg/L | <2 mg/L |
| Gentamicin — child | 7 mg/kg | Every 24h | — | <1 mg/L |
| Gentamicin — neonate <30 wk GA | 3 mg/kg | Every 48h | — | <1 mg/L |
| Gentamicin — neonate term (≥36 wk) | 4–5 mg/kg | Every 36h | — | <1 mg/L |
Aminoglycoside Antibiotics — Clinical Guide India
Amikacin and gentamicin are concentration-dependent aminoglycoside antibiotics active against aerobic Gram-negative bacilli (E. coli, Klebsiella, Pseudomonas, Acinetobacter) and, in combination, Gram-positive organisms including Staphylococcus aureus and Enterococcus. In India, they are indispensable for treating sepsis, complicated UTIs, hospital-acquired pneumonia, and neonatal sepsis — where Gram-negative multi-drug-resistant (MDR) organisms are common. Amikacin retains activity against gentamicin-resistant organisms and is preferred in settings with high aminoglycoside resistance.
Extended-interval (once-daily) vs traditional dosing
Extended-interval dosing (EID, once-daily) exploits aminoglycosides' concentration-dependent killing and post-antibiotic effect. A single large daily dose achieves higher peak:MIC ratios (driver of efficacy) and a longer drug-free trough period (reducing nephrotoxicity and ototoxicity). EID is the preferred strategy for most adult and paediatric patients outside of endocarditis synergy dosing. Contraindications to EID include: severe septic shock where continuous activity is critical, endocarditis (synergy dosing uses low-dose BD), pregnancy, and patients with rapidly fluctuating renal function.
IBW-based dosing in obese patients
Aminoglycosides distribute into body water, not fat. In obese patients (actual weight >120% IBW), dosing on actual weight causes toxicity while dosing on IBW alone may undertreat. The correct approach: use adjusted body weight (AdjBW) = IBW + 0.4 × (actual weight − IBW). This calculator computes IBW and AdjBW automatically from height, sex, and actual weight. For morbid obesity (BMI >40), specialist pharmacokinetic review is recommended.
Renal dose adjustment — interval extension
Aminoglycosides are renally excreted and accumulate with renal impairment, increasing nephrotoxicity and ototoxicity risk. The preferred strategy is to keep the same dose but extend the dosing interval — this maintains the peak:MIC ratio while reducing trough accumulation. As a general guide: CrCl 40–60 mL/min: extend OD amikacin to every 36 hours; CrCl 20–40 mL/min: every 48 hours; CrCl <20 mL/min: every 72 hours with TDM guidance. In acute kidney injury (AKI), check trough before each subsequent dose and only re-dose when trough is below target.
TDM — therapeutic drug monitoring — India context
TDM is mandatory for all patients on aminoglycosides beyond 48 hours, patients with renal impairment, neonates, and high-dose regimens. In many Indian hospitals, aminoglycoside TDM is underperformed — leading to both treatment failure (inadequate peaks) and toxicity (elevated troughs). Minimum TDM requirement: check a trough level before the 3rd dose in traditional dosing, or a random level 6–14 hours post-dose in once-daily dosing (plot on Hartford nomogram). Target trough for amikacin: <5 mg/L; for gentamicin: <1 mg/L (OD) or <2 mg/L (traditional). Send to any accredited biochemistry laboratory — ELISA-based aminoglycoside assays are available in most Indian cities.