What is the renally adjusted dose of gabapentin (Neurontin) for an adult patient with Acute Kidney Injury (AKI) and impaired renal function, specifically with a creatinine clearance (CrCl) of less than 60 mL/min?

Renally Adjusted Gabapentin Dosing in Acute Kidney Injury

For adult patients with AKI and creatinine clearance <60 mL/min, gabapentin requires dose reduction based on calculated CrCl using the Cockcroft-Gault equation, with total daily doses ranging from 100-1400 mg depending on severity of renal impairment. 1

Dose Adjustment Algorithm by Creatinine Clearance

The FDA-approved dosing for gabapentin in renal impairment provides specific guidance that applies directly to AKI patients 1:

CrCl 30-59 mL/min:

• Total daily dose: 400-1400 mg/day
• Dosing options: 200 mg BID, 300 mg BID, 400 mg BID, 500 mg BID, or 700 mg BID
• Start at lower end (200-300 mg BID) and titrate based on clinical response 1

CrCl 15-29 mL/min:

• Total daily dose: 200-700 mg/day
• Dosing options: 200 mg QD, 300 mg QD, 400 mg QD, 500 mg QD, or 700 mg QD
• Once-daily dosing reduces risk of accumulation 1

CrCl <15 mL/min (not on dialysis):

• Total daily dose: 100-300 mg/day
• Dosing options: 100 mg QD, 125 mg QD, 150 mg QD, 200 mg QD, or 300 mg QD
• For CrCl <15 mL/min, reduce daily dose in proportion to creatinine clearance (e.g., patients with CrCl of 7.5 mL/min should receive one-half the daily dose that patients with CrCl of 15 mL/min receive) 1

Hemodialysis Patients:

• Maintenance doses based on estimated CrCl as above
• Supplemental post-hemodialysis dose required: 125-350 mg after each 4-hour hemodialysis session 1
• Loading dose of 300-400 mg recommended for initiation 2
• Hemodialysis clearance of gabapentin is approximately 142 mL/min, removing ~35% of the dose per session 2

Critical Pharmacokinetic Considerations in AKI

Gabapentin is 100% renally excreted unchanged, making dose adjustment absolutely essential in any degree of renal impairment. 1, 3

• Elimination half-life increases from 5-9 hours with normal renal function to 132 hours in anuric patients 4, 2
• Plasma clearance is directly proportional to creatinine clearance 4
• No hepatic metabolism or protein binding, so renal function is the sole determinant of clearance 2

Calculating Creatinine Clearance

Use the Cockcroft-Gault equation to estimate CrCl, as this is the method validated for gabapentin dosing adjustments: 1

For males: CrCl = [(140 - age) × weight in kg] / (72 × serum creatinine in mg/dL)

For females: Multiply result by 0.85

This calculation is essential because eGFR equations (MDRD, CKD-EPI) are not appropriate for drug dosing decisions 1.

Monitoring and Safety in AKI

Patients with AKI require more frequent reassessment than those with stable CKD, as renal function can fluctuate rapidly: 5

• Monitor serum creatinine and recalculate CrCl every 24-48 hours during acute illness 5
• Watch for signs of gabapentin toxicity: altered mental status, somnolence, dizziness, ataxia, and falls 4, 6
• Epidemiological data show 19% increased risk of altered mental status, falls, and fractures with gabapentin use in dialysis patients 4
• Drug level monitoring is available and should be considered in AKI patients with neurological symptoms, though not routinely required 4

Common Prescribing Errors to Avoid

The most dangerous error is continuing pre-AKI doses without adjustment when renal function declines: 6

• Failure to reduce dose during acute illness can lead to severe neurotoxicity 6
• Off-label use should be reconsidered during AKI episodes, as risk-benefit ratio changes 6
• Review all medications during AKI, as gabapentin is among the drugs requiring temporary discontinuation or dose reduction when GFR <60 mL/min with serious intercurrent illness 5

Peritoneal Dialysis Considerations

For patients on peritoneal dialysis with AKI:

• Continuous automated cycling PD provides significant gabapentin clearance (94% of urea clearance) 7
• Elimination half-life with intensive PD is approximately 41 hours, substantially shorter than 132 hours without dialysis 7
• Dose adjustments similar to CrCl <15 mL/min are appropriate, with close monitoring 7

Practical Dosing Approach for AKI

Start with the lowest dose in the appropriate CrCl range and titrate slowly: 1

1. Calculate baseline CrCl using Cockcroft-Gault equation
2. Select starting dose from lower end of range for calculated CrCl
3. Reassess renal function daily during AKI
4. Adjust dose if CrCl changes by >25% or clinical toxicity develops
5. Consider discontinuation if indication is not compelling, given increased toxicity risk in AKI 5, 6