Gentamicin (IV)

Criteria & Principles

The full policy for aminoglycoside dosing by Pharmacy as set forth by the Clinical and Patient Care Services (CPCS) and Antimicrobial Stewardship and Evaluation Team (ASET) is available here.  The updated DUH Aminoglycoside Dosing and TDM Policy also includes guidance for Adult Cystic Fibrosis patients.

Note: A single dose of aminoglycoside may be an option to treat UTI.  Read more here.

Adjustment of Dose & Administration

Indication-Specific Adjustment

Selecting a Dosing Method

Initial Empiric Dosing

1. Select an appropriate aminoglycoside dosing method (refer above or Appendix A in the policy)
2. Determine dosing weight (DW) (see Appendix B of aminoglycoside dosing policy)

3. Calculate an appropriate loading dose for traditional dosing based upon indication.
   
   1. Gram-positive infection synergy or urinary tract infection: 1 mg/kg
   2. Bone/joint infection, cystic fibrosis, febrile neutropenia, GNR bacteremia/pneumonia, septic shock, or skin/soft tissue infection: 2.5 - 3 mg/kg
4. Determine maintenance dosing
   
   1. Traditional/conventional dosing: use Table E2 in PK policy to calculate a maintenance dose and interval
   2. Gram-positive synergy dosing (see table below)

c. Empiric Aminoglycoside Extended-interval Dosing (non-CF patients)

d. Cystic Fibrosis: Empiric Aminoglycoside Extended-interval Dosing

1. Gentamicin: 10 mg/kg q24h (max dose 700mg); only for patients with CrCl > 70 mL/min

Gentamicin doses will be rounded to the nearest 20 mg for doses >40 mg

Renal Adjustment

IHD, CRRT 

Use traditional dosing; extended-interval dosing is contraindicated

PD

For peritonitis in a peritoneal dialysis patient only, intraperitoneal administration is the preferred route. Confirm whether any IV doses have been administered before deciding upon a loading dose.

For use with Automated Peritoneal Dialysis (cycler): Tobramycin loading dose of 1.5 mg/kg IP in a long dwell (6 hours). Maintenance dose 0.5 mg/kg IP in a long dwell.

For use with Continuous Ambulatory Peritoneal Dialysis (manual exchanges):

Treatment path 1 (Intermittent dosing with gentamicin or tobramycin): no loading dose. Maintenance doses of 0.6 mg/kg IP once administered in a dwell

Treatment path 2 (continuous dosing with gentamicin or tobramycin): Loading dose of 8 mg per liter of dialysate administered IP once in a dwell. Maintenance dose of 4 mg per liter of dialysate administered IP in every exchange. *NOTE: dosing for this treatment path is not based on body weight* 

Serum Concentration Monitoring

Maintenance concentrations should be monitored at least once weekly, and considered at least every 3rd day in patients demonstrating acute changes in renal function, fluid status, etc. 

Laboratory monitoring: SCr and BUN should be measured at baseline and at least 2x weekly

See the aminoglycoside dosing policy (table E4 and E5) for timing of concentration draws and goal peak/trough values

Drug-Specific Information

CLSI has revised their breakpoints for aminoglycosides (see below). However, there is a lag between updates and FDA device-breakpoint validation. For patients requiring systemic therapy, please run the MIC report to confirm susceptibility.

General Notes

1. Up-to-date cost information, click here 
2. IV antimicrobials outpatient (OPAT) dosing, click here
3. Obesity dosing weight recommendations here
4. Helpful drug-drug interaction check website here 
5. When dosing guidance is provided it is important to note the following:

Fixed (ie non weight-based) doses in adults are historically based on a 70 kg patient. Specific disease states or individual patients may warrant dosages that differ from the above recommendations. Since product-specific criteria for dose adjustment based on creatinine clearance exist, consult product information regarding specific recommendations for dosage adjustment based on estimated creatinine clearance.