Gabapentin is the 11th most commonly prescribed drug in the United States, with over 46,043,168 prescriptions in 2020 so far. Considering how widely used this drug is, it pays to know a little more about this medication, including how long gabapentin stays in your system.
How long does gabapentin stay in your system?
Gabapentin is likely detectable in your system for the following time frames:
Urine: 1 to 2 days after last use
Saliva: Up to 36 hours after last use
Plasma: Gabapentin is largely excreted via the renal system and does not largely bind to plasma proteins; since the elimination half-life is about 7 hours, that means it could take up to 35 hours for the body to completely clear this drug, although the detection window for gabapentin in blood tests is much likely much shorter, perhaps only within the first 5 to 7 hours after last dose
Hair: Potentially up to 90 days after last use, although accuracy may be low
(Numbers above are merely estimates, and may vary based on several factors, such as age and other medical conditions.)
Bio-Availability of Gabapentin
According to the FDA, gabapentin in 3 divided doses has an oral bioavailability of:
- 60% (900 mg/day)
- 47% (1,200 mg/day)
- 34% (2,400 mg/day)
- 33% (3,600 mg/day)
- 27% (4,800 mg/day)
The body does not sufficiently metabolize gabapentin. Instead, it is excreted through the renal (kidney) system as an unchanged drug.
What is the half-life of gabapentin?
In adult patients, the half-life of gabapentin is about 5 to 7 hours. In other words, it takes the body about 5 to 7 hours to eliminate its gabapentin concentration by half. This estimate can be altered by many factors including but not limited to kidney function.
Half-life for pediatric patients is roughly 4.7 hours. This estimate can be altered by many factors included but not limited to kidney function.
Adult Patients with Decreased Kidney Function
For adults with renal impairment, half-life can vary wildly, from 6.5 hours to 52 hours depending on kidney function.
Anuric Adult Patients
For anuric patients (without dialysis), gabapentin half-life is roughly 132 hours.
How long does it take for gabapentin to kick in?
Some patients report gabapentin kicks in soon after their first dose, while others do not experience full effects for up to 2 weeks.
How much gabapentin can you take in a day?
For more information, please visit our gabapentin dosage page.