What is the recommended monitoring protocol for patients taking gabapentin (Neurontin)?

Monitoring for Gabapentin Use

Gabapentin requires renal function monitoring and dose adjustment based on creatinine clearance, with clinical surveillance for neurological adverse effects including dizziness, somnolence, altered mental status, and fall risk, particularly at doses ≥600 mg/day.

Renal Function Monitoring

Mandatory renal monitoring is essential because gabapentin is excreted unchanged in urine, with plasma clearance directly proportional to creatinine clearance. 1, 2

• Calculate baseline creatinine clearance before initiating therapy using the Cockcroft-Gault equation, as gabapentin dosing must be adjusted based on renal function 1
• Monitor creatinine clearance periodically during treatment, especially in elderly patients who are more likely to have declining renal function 1
• In patients with renal impairment, the elimination half-life increases dramatically from 5-9 hours in normal function to 132 hours in dialysis patients 2
• Dose adjustments are required for creatinine clearance <60 mL/min, with specific dosing tables provided in the FDA label 1

Clinical Monitoring for Adverse Effects

Monitor closely for neurological adverse effects, which show a clear dose-response relationship and are the primary safety concern with gabapentin. 3

Falls and Fractures

• Gabapentin increases fall and fracture risk with a relative risk of 1.35, with incidence of 1.81 per 100 person-years in exposed patients versus 1.34 in unexposed patients 3
• Risk escalates significantly at doses ≥2,400 mg/day (RR 1.90), demonstrating a clear dose-response relationship 3
• Elderly patients require particularly vigilant monitoring as they have both higher baseline fall risk and are more likely to have decreased renal function 1, 3

Altered Mental Status

• Monitor for confusion, somnolence, and altered mental status, which occurs at an incidence of 1.08 per 100 person-years in exposed patients (RR 1.12) 3
• Risk is elevated at doses 600-2,399 mg/day, though the dose-response relationship is less clear at higher doses due to limited data 3
• These symptoms are often transient and occur around the onset of dosing 4

High-Risk Populations

• Patients with hepatitis C, HIV, or alcohol use disorder have elevated baseline incidence of adverse events regardless of gabapentin exposure, though excess risk from gabapentin may be less apparent in these groups 3
• Patients on hemodialysis require supplemental dosing after each 4-hour dialysis session and are at particularly high risk for overdose if not properly monitored 1, 2

Therapeutic Drug Monitoring

Therapeutic drug monitoring is possibly useful but not routinely required for most patients. 5

• Plasma concentrations during clinical studies generally ranged between 2-20 mg/L 5
• Consider therapeutic drug monitoring in specific situations: patients with renal insufficiency requiring dose adjustment, those with suspected overdose presenting with severe neurological symptoms, or when interindividual pharmacokinetic variability complicates dosing 2, 5
• The broad therapeutic index and lack of drug interactions with other anticonvulsants make routine monitoring less critical than with other antiepileptic drugs 5

Monitoring During Dose Titration

• Assess tolerability during titration, particularly when using faster titration schedules or higher maintenance doses 4
• Maximum time between doses should not exceed 12 hours to maintain therapeutic levels 1
• If discontinuing or reducing gabapentin, taper gradually over a minimum of 1 week to avoid withdrawal symptoms 1

Abuse Potential Monitoring

• Screen for abuse risk factors: history of opioid abuse, mental illness, or previous prescription drug abuse 6
• Be aware that gabapentin may be abused for euphoria, potentiating opioid effects, or sedation, particularly in high-risk populations 6
• Some states now track gabapentin through prescription monitoring programs 6