What is the recommended daily dose of amikacin (antibiotic) for an 80-year-old male patient weighing 63 kg with normal renal function?

Amikacin Dosing for an 80-Year-Old Male with Normal Renal Function

For an 80-year-old male weighing 63 kg with normal renal function, the recommended dose of amikacin is 10 mg/kg/day (630 mg) administered as a single daily dose. 1, 2

Dosing Algorithm

1. Age-based adjustment:

   • For patients over 59 years of age: 10 mg/kg/day (reduced from standard 15 mg/kg/day) 2
   • For this 80-year-old patient: 10 mg/kg × 63 kg = 630 mg daily

2. Administration method:

   • Intramuscular or intravenous as a single daily dose 2
   • If intravenous, administer over 30-60 minutes 1

3. Duration and monitoring:

   • Usual duration is 7-10 days 1
   • Limit treatment to short term whenever feasible
   • For difficult infections where treatment beyond 10 days is needed, re-evaluate use and monitor:
     • Serum amikacin levels
     • Renal function
     • Auditory and vestibular function

Important Considerations

• Concentration-dependent bactericidal effect: Single daily dosing takes advantage of this pharmacodynamic property while potentially reducing toxicity 2

• Toxicity monitoring: Baseline and periodic monitoring is essential 2

  • Baseline: audiogram, vestibular testing, Romberg testing, serum creatinine
  • Monthly: renal function assessment, questioning about auditory/vestibular symptoms
  • Repeat audiogram and vestibular testing if eighth nerve toxicity symptoms develop

• Response assessment: Uncomplicated infections should respond within 24-48 hours; if no definite clinical response within 3-5 days, therapy should be stopped and susceptibility rechecked 1

• Total daily dose limit: Should not exceed 15 mg/kg/day by all routes of administration 1

Potential Adverse Effects

• Ototoxicity: May cause deafness (24% high-frequency hearing loss in one report) 2

  • Risk increases with concurrent diuretic use
  • Higher rates with longer treatment and higher doses

• Nephrotoxicity: More nephrotoxic than streptomycin 2

  • Renal impairment seen in 8.7% of patients receiving amikacin
  • Higher risk with initially increased creatinine levels, larger total doses, and concurrent nephrotoxic agents

Special Considerations for Elderly Patients

• Elderly patients often have reduced creatinine clearance even with "normal" serum creatinine levels 3, 4
• Careful monitoring of renal function is essential even when baseline values appear normal
• If any signs of declining renal function develop, adjust dosing frequency (maintain dose at 12-15 mg/kg but reduce to 2-3 times weekly) 2

This dosing recommendation prioritizes both efficacy and safety for this elderly patient while maintaining therapeutic drug levels to effectively treat the infection.