For the selected aminoglycoside, administer a loading dose to provide peak serum levels. The Ideal Body Weight is recommended for calculating the loading dose, rather than the actual weight, because of the low therapeutic index for the aminoglycosides. For obese patients, a body weight between the ideal and actual body weight is used (see below).
Calculate the Loading Dose
|
|
usual LD |
EPSL |
|
Amikacin |
5.0 - 7.5 |
15 - 30 |
|
Gentamicin |
1.5 - 2.0 |
4 - 10 |
|
Netilimicin |
1.5 - 2.0 |
4 - 10 |
|
Tobramycin |
1.5 - 2.0 |
4 - 10 |
where:
• LD = loading doses, in mg/kg
• EPSL = expected peak serum levels, in µg/mL
Estimate the Creatinine Clearance
To calculate creatinine clearance from serum creatinine, see:
• Cockcroft and Gault (Nephron 1976)]
• Creatinine Clearance from Serum Creatinine]
Calculate the Maintenance Dose as Percent of Loading Dose
Step 1: decide on dosing interval desired (8, 12 or 24 hours).
Step 2: calculate the patient's creatinine clearance.
Step 3: the percentage value from the table is the percentage of the loading dose that should be administered as the maintenance dose:
|
Cr Cl in mL/min |
half life in hours |
8 hrs |
12 hrs |
24 hrs |
|
90 |
3.1 |
84% |
|
|
|
80 |
3.4 |
80% |
91% |
|
|
70 |
3.9 |
76% |
88% |
|
|
60 |
4.5 |
71% |
84% |
|
|
50 |
5.3 |
65% |
79% |
|
|
40 |
6.5 |
57% |
72% |
92% |
|
30 |
8.4 |
48% |
63% |
86% |
|
25 |
9.9 |
43% |
57% |
81% |
|
20 |
11.9 |
37% |
50% |
75% |
|
17 |
13.6 |
33% |
46% |
70% |
|
15 |
15.1 |
31% |
42% |
67% |
|
12 |
17.9 |
27% |
37% |
61% |
|
10 |
20.4 |
24% |
34% |
56% |
|
7 |
25.9 |
19% |
28% |
47% |
|
5 |
31.5 |
16% |
23% |
41% |
|
2 |
46.8 |
11% |
16% |
30% |
|
0 |
69.3 |
8% |
11% |
21% |
For gentamicin and tobramycin:
(1) if dose is 50 - 120 mg, then round off to the nearest 10 mg.
(2) if dose > 120 mg, then round off to the nearest 20 mg.
For amikacin:
(1) round off to the nearest 50 mg.
Further dosage adjustments must be based on serum levels and changes in the patient's condition.
Specialty: Infectious Diseases, Pharmacology, clinical, Nephrology
