How do you adjust medications in a patient with Acute Kidney Injury (AKI)?

Medication Management in Acute Kidney Injury

Drug selection, dosing, and monitoring in patients with Acute Kidney Injury (AKI) should be guided by the functional phase, trajectory, and stage of AKI, with individualized assessment of medication regimens to prevent further kidney damage and optimize outcomes. 1

Key Principles for Medication Management in AKI

Assessment and Monitoring

• Medication reconciliation should occur at AKI diagnosis, when AKI phase changes, and when the patient's condition changes 2
• Monitor renal function parameters regularly to guide medication adjustments and detect worsening kidney function 1
• Use therapeutic drug monitoring when available to guide dosing of medications with narrow therapeutic windows 3

Medication Selection Considerations

• Evaluate the route of excretion (renal versus non-renal) when selecting medications 1
• Assess nephrotoxic potential of all medications and avoid nephrotoxic combinations whenever possible 1
• Consider the effect of AKI on drug metabolites and non-renal metabolism of drugs 1
• Evaluate the urgency and strength of indications for each medication 1
• Identify suitable alternatives with less nephrotoxic potential 1

Specific Medication Adjustments

Nephrotoxic Medications

• Avoid nephrotoxic medications or combinations whenever possible in patients with AKI 1
• Each additional nephrotoxin increases the odds of developing or worsening AKI by 53% 4
• When nephrotoxic medications are necessary for compelling clinical reasons, implement strategies to mitigate toxicity 1
• Common nephrotoxic medications requiring special attention include:
  • Aminoglycosides (e.g., gentamicin) 3, 5
  • ACE inhibitors and ARBs 1
  • NSAIDs 1, 6
  • Vancomycin 6, 5
  • Contrast media 7

Dosing Adjustments for Impaired Renal Function

• For medications with predominant renal excretion, adjust dosing based on estimated kidney function 3
• Two main approaches to dose adjustment in AKI: 3
  1. Increase the interval between doses while maintaining the standard dose
  2. Reduce the dose while maintaining the standard interval

Specific Dosing Guidelines

• For gentamicin and other aminoglycosides: 3
  • The interval between doses (in hours) can be approximated by multiplying serum creatinine (mg/dL) by 8
  • Example: For a patient with serum creatinine of 2 mg/dL, administer gentamicin every 16 hours (2 × 8)
  • Alternatively, divide the normal dose by the serum creatinine level for dosing at regular intervals
  • Monitor peak and trough levels to ensure therapeutic but not toxic concentrations
  • Peak levels should not exceed 12 μg/mL and trough levels should remain below 2 μg/mL 3

Special Considerations

ACE Inhibitors and ARBs

• ACE inhibitors and ARBs are associated with functional AKI, particularly in hypovolemic states 1
• Consider temporarily discontinuing these medications during the acute phase of AKI 1
• A UK study showed that a 16% increase in ACE inhibitor and ARB prescribing corresponded with a 50% increase in hospital admissions complicated by AKI 1

Patients on Renal Replacement Therapy (RRT)

• RRT affects drug dosing, nutritional support, and nephrotoxin accumulation 1
• For patients on hemodialysis, the amount of drug removed varies based on dialysis method 3
• After hemodialysis, supplemental doses may be required for certain medications 3
• For patients on continuous RRT, different dosing strategies are needed compared to intermittent hemodialysis 1

Practical Approach to Medication Management in AKI

1. Assess AKI severity and phase 1
2. Review all current medications for nephrotoxic potential 1
3. Discontinue or find alternatives for non-essential nephrotoxic drugs 1
4. Adjust dosages based on estimated kidney function 3
5. Implement monitoring plan including renal function tests and therapeutic drug monitoring 1
6. Reassess regularly as kidney function changes 3

Common Pitfalls to Avoid

• Failing to recognize that deteriorating renal function may require greater dose reductions than stable renal impairment 3
• Combining multiple nephrotoxic medications, which significantly increases AKI risk 1, 4
• Overlooking drug interactions that may increase nephrotoxicity 1
• Assuming stable kidney function during the course of AKI 3
• Inadequate monitoring of drug levels for medications with narrow therapeutic windows 1