How to order amikacin for adults with normal or impaired renal function?

Amikacin Dosing Guidelines for Adults with Normal and Impaired Renal Function

For adults with normal renal function, amikacin should be ordered at 15 mg/kg/day (maximum 1 g/day) as a single daily dose given intravenously or intramuscularly, with dose adjustments based on renal function and age. 1

Standard Dosing for Normal Renal Function

Adults with Normal Renal Function

• Dose: 15 mg/kg/day (maximum 1 g/day)
• Administration: Intravenous or intramuscular
• Frequency: Single daily dose (5-7 days/week)
• Duration: Initially daily, then reducing to 2-3 times per week after 2-4 months or after culture conversion 1
• Age adjustment: For patients >59 years, reduce dose to 10 mg/kg/day (maximum 750 mg/day) 1

Preparation

• Available as aqueous solution in vials of 500 mg and 1 g
• For IV administration: Add to 100-200 mL of compatible solution (0.9% sodium chloride or 5% dextrose)
• Administer over 30-60 minutes 2

Dosing for Impaired Renal Function

Renal function impairment requires dosage adjustments due to increased risk of ototoxicity and nephrotoxicity 1:

Method 1: Normal Dose at Extended Intervals

• If creatinine clearance is unavailable and patient is stable:
• Calculate dosing interval (hours) = patient's serum creatinine × 9
• Example: If serum creatinine is 2 mg/dL, give normal dose (15 mg/kg) every 18 hours 2

Method 2: Reduced Dose at Fixed Intervals

• Start with normal loading dose (15 mg/kg)
• For maintenance doses every 12 hours:
  • Maintenance dose = (observed CrCl ÷ normal CrCl) × loading dose
• Alternative calculation: Divide normal dose by patient's serum creatinine 2

Hemodialysis Patients

• Maintain dose at 12-15 mg/kg
• Reduce frequency to 2-3 times per week
• Administer after dialysis to prevent premature drug removal 1

Monitoring

Required Baseline Tests

• Audiogram
• Vestibular testing
• Romberg testing
• Serum creatinine measurement 1

Ongoing Monitoring

• Monthly assessment of renal function
• Monthly questioning about auditory/vestibular symptoms
• Repeat audiogram and vestibular testing if symptoms of eighth nerve toxicity develop
• Serum drug concentrations (advantage of amikacin is routine availability of measurements) 1
• Target peak levels: 20-35 μg/mL
• Target trough levels: <10 μg/mL 2

Important Considerations and Cautions

Potential Adverse Effects

• Ototoxicity: Can cause deafness (24% high-frequency hearing loss with higher rates at longer treatment/higher doses) 1
• Nephrotoxicity: Renal impairment in 8.7% of patients, higher with pre-existing elevated creatinine, larger total doses, or concurrent nephrotoxic agents 1

Special Populations

• Pregnancy: Contraindicated due to risk of fetal nephrotoxicity and congenital hearing loss 1
• Hepatic disease: No dose adjustments necessary, but monitor renal function closely in severe hepatic disease due to risk of hepato-renal syndrome 1

Clinical Pearls

• Once-daily dosing may be more effective and less toxic than divided doses 3, 4
• Do not physically premix amikacin with other drugs 2
• Treatment failure may occur if dosing is inadequate in renal impairment; maintain adequate dose (12-15 mg/kg) but extend interval 1
• Therapeutic drug monitoring is essential in patients with renal impairment to avoid toxicity 1

By following these guidelines, you can optimize amikacin therapy while minimizing the risk of adverse effects, particularly in patients with renal impairment.