What is the recommended dose of amikacin (antibiotic) for a 50kg male with tubercular meningitis?

Amikacin Dosing for Tubercular Meningitis in a 50kg Male

For a 50kg male with tubercular meningitis, the recommended dose of amikacin is 15 mg/kg/day (750 mg daily) administered parenterally as a single daily dose. 1, 2, 3

Standard Dosing Regimen

• The Centers for Disease Control and Prevention recommends amikacin at 15 mg/kg/day for adults with tuberculosis, typically administered as a single daily dose (5-7 days/week) initially 1
• For a 50kg patient, this translates to 750 mg daily 2, 3
• After the first 2-4 months or after culture conversion, the frequency can be reduced to two or three times a week, depending on the efficacy of other drugs in the regimen 1
• The maximum daily dose should not exceed 1 gram 1, 2

Administration Methods

• Amikacin can be administered either intramuscularly or intravenously 2, 3
• For intravenous administration, the dose should be diluted in 100-200 mL of compatible solution (such as 0.9% sodium chloride or 5% dextrose) and administered over 30-60 minutes 2
• The total daily dose by all routes of administration should not exceed 15 mg/kg/day 2

Monitoring Requirements

• Baseline assessment should include audiogram, vestibular testing, Romberg testing, and serum creatinine measurement 1
• Peak serum concentrations should be measured 30-90 minutes after injection and should not exceed 35 μg/mL 2, 3
• Trough concentrations (just prior to the next dose) should remain below 10 μg/mL 2, 3
• Monthly assessments of renal function and questioning regarding auditory or vestibular symptoms should be performed 1
• Audiogram and vestibular testing should be repeated if symptoms of eighth nerve toxicity develop 1

Duration of Treatment

• The usual duration of treatment is 7-10 days for most infections, but may be longer for tubercular meningitis 2, 3
• For difficult and complicated infections where treatment beyond 10 days is considered, amikacin use should be reevaluated 2
• If treatment is continued beyond 10 days, amikacin serum levels and renal, auditory, and vestibular functions should be closely monitored 2, 3

Special Considerations

• For patients over 59 years of age, the dose should be reduced to 10 mg/kg/day (500 mg for a 50kg patient) 1, 4
• In patients with renal impairment, the dosing frequency should be reduced while maintaining the mg/kg dose at 12-15 mg/kg to ensure concentration-dependent bactericidal effect 1, 5
• Amikacin has poor penetration into the cerebrospinal fluid, even in patients with meningitis, which may necessitate higher systemic doses to achieve therapeutic levels in the CNS 1

Potential Adverse Effects

• Ototoxicity (vestibular and hearing disturbances) is the most important adverse reaction 1
• Risk of ototoxicity increases with age, concomitant use of loop-inhibiting diuretics, increasing single doses, and cumulative dose (especially above 100-120g) 1, 6
• Nephrotoxicity occurs less commonly with amikacin than with other aminoglycosides but should still be monitored 1
• Circumoral paresthesias immediately after injection are relatively common 1

By following these dosing guidelines and implementing appropriate monitoring, amikacin can be effectively and safely used as part of a regimen for treating tubercular meningitis in a 50kg male patient.