Amikacin dosage and administration

# Dosage and Administration
The patient's pretreatment body weight should be obtained for calculation of correct dosage. Amikacin sulfate injection may be given intramuscularly or intravenously.
The status of renal function should be estimated by measurement of the serum creatinine concentration or calculation of the endogenous creatinine clearance rate. The blood urea nitrogen (BUN) is much less reliable for this purpose. Reassessment of renal function should be made periodically during therapy.
Whenever possible, amikacin concentrations in serum should be measured to assure adequate but not excessive levels. It is desirable to measure both peak and trough serum concentrations intermittently during therapy. Peak concentrations (30 to 90 minutes after injection) above 35 mcg/mL and trough concentrations (just prior to the next dose) above 10 mcg/mL should be avoided. Dosage should be adjusted as indicated.

### Intramuscular Administration for Patients with Normal Renal Function
The recommended dosage for adults, children and older infants (see WARNINGS box) with normal renal function is 15 mg/kg/day divided into 2 or 3 equal doses administered at equally divided intervals, i.e., 7.5 mg/kg q12h or 5 mg/kg q8h. Treatment of patients in the heavier weight classes should not exceed 1.5 g/day.
When amikacin is indicated in newborns (see WARNINGS box), it is recommended that a loading dose of 10 mg/kg be administered initially to be followed with 7.5 mg/kg every 12 hours.
The usual duration of treatment is 7 to 10 days. It is desirable to limit the duration of treatment to short-term whenever feasible. The total daily dose by all routes of administration should not exceed 15 mg/kg/day. In difficult and complicated infections where treatment beyond 10 days is considered, the use of amikacin should be reevaluated. If continued, amikacin serum levels and renal, auditory and vestibular functions should be monitored. At the recommended dosage level, uncomplicated infections due to amikacin-sensitive organisms should respond in 24 to 48 hours. If definite clinical response does not occur within 3 to 5 days, therapy should be stopped and the antibiotic susceptibility pattern of the invading organism should be rechecked. Failure of the infection to respond may be due to resistance of the organism or to the presence of septic foci requiring surgical drainage.
When amikacin is indicated in uncomplicated urinary tract infections, a dose of 250 mg twice daily may be used.

### Intramuscular Administration for Patients with Impaired Renal Function
Whenever possible, serum amikacin concentrations should be monitored by appropriate assay procedures. Doses may be adjusted in patients with impaired renal function either by administering normal doses at prolonged intervals or by administering reduced doses at a fixed interval.
Both methods are based on the patient's creatinine clearance or serum creatinine values since these have been found to correlate with aminoglycoside half-lives in patients with diminished renal function. These dosage schedules must be used in conjunction with careful clinical and laboratory observations of the patient and should be modified as necessary.
Neither method should be used when dialysis is being performed.

### Normal Dosage at Prolonged Intervals
If the creatinine clearance rate is not available and the patient's condition is stable, a dosage interval in hours for the normal dose can be calculated by multiplying the patient's serum creatinine by 9, e.g., if the serum creatinine concentration is 2 mg/100 mL, the recommended single dose (7.5 mg/kg) should be administered every 18 hours.

### Reduced Dosage at Fixed Time Intervals
When renal function is impaired and it is desirable to administer amikacin at a fixed time interval, dosage must be reduced. In these patients, serum amikacin concentrations should be measured to assure accurate administration of amikacin and to avoid concentrations above 35 mcg/mL. If serum assay determinations are not available and the patient's condition is stable, serum creatinine and creatinine clearance values are the most readily available indicators of the degree of renal impairment to use as a guide for dosage.
First, initiate therapy by administering a normal dose, 7.5 mg/kg, as a loading dose. This loading dose is the same as the normally recommended dose which would be calculated for a patient with a normal renal function as described above.
To determine the size of maintenance doses administered every 12 hours, the loading dose should be reduced in proportion to the reduction in the patient's creatinine clearance rate:
An alternate rough guide for determining reduced dosage at 12 hour intervals (for patients whose steady state serum creatinine values are known) is to divide the normally recommended dose by the patient's serum creatinine.
The above dosage schedules are not intended to be rigid recommendations but are provided as guides to dosage when the measurement of amikacin serum levels is not feasible.

### Intravenous Administration
The individual dose, the total daily dose, and the total cumulative dose of amikacin sulfate are identical to the dose recommended for intramuscular administration. The solution for intravenous use is prepared by adding the contents of a 500 mg vial to 100 or 200 mL of sterile diluent such as 0.9% sodium chloride injection or 5% dextrose injection or any other compatible solutions listed below.
The solution is administered to adults over a 30 to 60 minute period. The total daily dose should not exceed 15 mg/kg/day and may be divided into either 2 or 3 equally-divided doses at equally-divided intervals.
In pediatric patients, the amount of fluid used will depend on the amount of amikacin sulfate ordered for the patient. It should be a sufficient amount to infuse the amikacin over a 30 to 60 minute period. Infants should receive a 1 to 2 hour infusion.
Amikacin should not be physically premixed with other drugs but should be administered separately according to the recommended dose and route.

### Stability in IV Fluids
Amikacin sulfate is stable for 24 hours at room temperature at concentrations of 0.25 and 5 mg/mL in the following solutions:
5% Dextrose Injection USP
5% Dextrose USP and 0.2% Sodium Chloride Injection USP
5% Dextrose USP and 0.45% Sodium Chloride Injection USP
0.9% Sodium Chloride Injection USP
Lactated Ringer's Injection USP
Normosol M in 5% Dextrose Injection USP (or Plasma-Lyte 56 injection in 5% Dextrose USP in water).
Normosol R in 5% Dextrose Injection USP (or Plasma-Lyte 148 injection in 5% Dextrose USP in water).
In the above solutions with amikacin sulfate concentrations of 0.25 and 5 mg/mL, solutions aged for 60 days at 4C and then stored at 25C had utility times of 24 hours.
At the same concentrations, solutions frozen and aged for 30 days at -15C, thawed, and stored at 25C had utility times of 24 hours.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.
Aminoglycosides administered by any of the above routes should not be physically premixed with other drugs but should be administered separately.
Because of the potential toxicity of aminoglycosides, "fixed dosage" recommendations which are not based upon body weight are not advised. Rather, it is essential to calculate the dosage to fit the needs of each patient.