What is the recommended intravenous (IV) dose of Amikacin for the treatment of serious bacterial infections, administered every 12 hours?

Amikacin IV Dosing Every 12 Hours

For adults with normal renal function, amikacin should be dosed at 7.5 mg/kg IV every 12 hours (or alternatively 5 mg/kg every 8 hours), with a maximum total daily dose not exceeding 15 mg/kg/day. 1

Standard Adult Dosing

• The FDA-approved regimen is 15 mg/kg/day divided into 2 or 3 equal doses at equally-divided intervals (7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours) 1
• Treatment duration should typically be 7-10 days, with total daily dose by all routes not exceeding 15 mg/kg/day 1
• For patients in heavier weight classes, the total daily dose should not exceed 1.5 grams/day 1

Once-Daily Dosing Alternative

While you asked about 12-hourly dosing, once-daily dosing at 15 mg/kg IV every 24 hours is an effective and practical alternative that may reduce nephrotoxicity risk 2, 3:

• Once-daily dosing showed 83.1% primary success and 83.9% definitive cure in severely infected patients 3
• This regimen is particularly effective for bloodstream infections and complicated urinary tract infections 2
• Once-daily dosing provides superior pharmacokinetic advantages, maintaining serum levels above 10 times the MIC for 75% of the dosing interval 4

Pediatric Dosing (12-Hourly Context)

For children and older infants with normal renal function:

• 15 mg/kg/day divided every 8 hours or 15-22.5 mg/kg/dose once daily 5, 2
• For neonates, dosing varies significantly by gestational and postnatal age, ranging from 15 mg/kg/dose every 48 hours to every 24 hours depending on maturity 5

Specific Clinical Scenarios

For complicated urinary tract infections due to carbapenem-resistant Enterobacterales (CRE):

• Plazomicin (a newer aminoglycoside) is dosed at 15 mg/kg IV every 12 hours 5
• Single-dose aminoglycoside is recommended for simple cystitis due to CRE 5

For Mycobacterium abscessus infections:

• 10-15 mg/kg daily IV (lower dose of 10 mg/kg for patients >50 years or anticipated long-term therapy ≥3 weeks) 5
• Three-times-weekly dosing at 25 mg/kg is reasonable but may be difficult to tolerate beyond 3 months 5

Critical Monitoring Requirements

Therapeutic drug monitoring is strongly recommended to optimize efficacy and reduce toxicity 2:

• Target peak concentrations: 30-90 minutes after injection, aiming for levels in the low 20s mcg/mL range 1
• Peak concentrations above 35 mcg/mL should be avoided 1
• Trough concentrations above 10 mcg/mL should be avoided 1
• Monitor renal function regularly and avoid concomitant nephrotoxic drugs 2

Renal Impairment Adjustments

For patients with impaired renal function receiving 12-hourly dosing:

• Calculate dosing interval by multiplying serum creatinine by 9 (e.g., if creatinine is 2 mg/dL, give normal dose every 18 hours) 1
• Alternatively, reduce the dose proportionally: Maintenance dose = (observed creatinine clearance/normal creatinine clearance) × calculated loading dose, given every 12 hours 1
• Always initiate with a loading dose of 7.5 mg/kg regardless of renal function 1

Administration Details

• Infuse over 30-60 minutes in adults 1
• Infants should receive a 1-2 hour infusion 1
• Amikacin should not be physically premixed with other drugs but administered separately 1

Common Pitfalls

• Nephrotoxicity risk: Studies show 6-20% incidence depending on dosing regimen, with once-daily potentially safer than divided dosing 3, 4
• Ototoxicity risk: Occurs in 8-16% of patients; monitor auditory and vestibular function during prolonged therapy 4, 6
• Inadequate response: If no clinical response within 3-5 days, stop therapy and recheck antibiotic susceptibility patterns 1
• Resistance patterns: Bacteria associated with treatment failures include Pseudomonas, Acinetobacter, and Staphylococcus species 3