What is the maintenance dose for a 108kg patient at 15mg/kg?

Maintenance Dose Calculation for 108 kg Patient at 15 mg/kg

For a 108 kg patient requiring 15 mg/kg dosing, administer 1,620 mg (15 mg/kg × 108 kg), but do not exceed the maximum dose of 1,000 mg per day for most injectable aminoglycosides and similar agents. 1

Dosing Algorithm

Step 1: Determine the Drug Class and Maximum Dose

• For aminoglycosides (amikacin, kanamycin) and capreomycin: The standard adult dose is 15 mg/kg per day with a maximum of 1,000 mg/day 1
• For patients >59 years: Reduce to 10 mg/kg per day (maximum 750 mg) 1

Step 2: Calculate Based on Body Weight Considerations

• For drugs with limited adipose distribution (aminoglycosides, neuromuscular blockers): Use ideal body weight (IBW) for dosing 2, 3, 4
• For highly lipophilic drugs: Consider total body weight, but this patient's weight suggests possible obesity requiring adjustment 2, 5
• For obese patients on aminoglycosides: Use IBW + 40% of excess weight for dose calculation 6

Step 3: Apply the Calculation

• Standard calculation: 15 mg/kg × 108 kg = 1,620 mg
• However, the maximum daily dose is 1,000 mg for most injectable second-line TB drugs 1
• Therefore, administer 1,000 mg as the maintenance dose 1

Frequency Adjustments

Initial Phase (First 2-4 Months)

• Administer as a single daily dose, 5-7 days per week 1

Maintenance Phase (After Culture Conversion)

• Reduce frequency to 2-3 times weekly 1
• Maintain the milligram dose at 12-15 mg/kg per dose (up to 1,000 mg) to preserve concentration-dependent bactericidal effect 1
• Smaller doses may reduce drug efficacy 1

Critical Monitoring Requirements

Baseline Assessment

• Audiogram, vestibular testing, Romberg testing 1
• Serum creatinine measurement 1

Ongoing Monitoring

• Serum drug concentrations: Measure peak levels within the first week 6
• Target trough level: <5 mg/L 6
• Target peak level: 25-35 mg/L (daily dosing) or 65-80 mg/L (three times weekly dosing) 6
• Monthly renal function assessment and questioning about auditory/vestibular symptoms 1

Important Caveats

Renal Impairment Considerations

• If renal insufficiency develops, reduce dosing frequency to 2-3 times weekly but maintain the 12-15 mg/kg per dose 1
• Administer after dialysis in hemodialysis patients 1

Toxicity Risks

• Nephrotoxicity: Occurs in 8.7% of patients receiving amikacin, higher with elevated baseline creatinine 1
• Ototoxicity: High-frequency hearing loss in up to 24% with longer treatment/higher doses 1
• Both risks increase significantly with concurrent nephrotoxic agents or diuretics 1