Two adult starts share one 300 mg capsule
The yellow 300 mg capsule is printed Neurontin/300 mg. The same label also lists a white 100 mg capsule, an orange 400 mg capsule, scored 600 mg and 800 mg tablets, and an oral solution of 250 mg per 5 mL. Those are strengths, not a menu to mix on your own.
Postherpetic neuralgia in adults uses a three-day climb. Day 1 is a single 300 mg dose, day 2 is 600 mg/day (300 mg two times a day), and day 3 is 900 mg/day (300 mg three times a day). If pain relief still needs a higher total, the dose can move to 1800 mg/day, which is 600 mg three times a day. Clinical studies showed an effect from 1800 mg/day to 3600 mg/day, with comparable effects across that range. In those studies, the additional benefit of using doses greater than 1800 mg/day was not demonstrated. Climbing past 1800 mg because the bottle still has capsules is not what that sentence supports.
Add-on treatment of partial-onset seizures, with or without secondary generalization, is the other labeled use. For patients 12 years of age and older, the starting dose is 300 mg three times a day. The recommended maintenance dose is 300 mg to 600 mg three times a day. Dosages up to 2400 mg/day were used in long-term studies. Doses of 3600 mg/day were given to a small number of patients for a relatively short time. That short exposure is not a goal to copy from a 300 mg start.
Children 3 to 11 years are on a milligram-per-kilogram schedule: a start of 10 to 15 mg/kg/day in three doses, then about 40 mg/kg/day at ages 3 to 4, or 25 to 35 mg/kg/day at ages 5 to 11. The use of Neurontin in patients less than 12 years of age with compromised renal function has not been studied. This page does not turn the adult 300 mg ladder into a child dose.
The kidney column is creatinine clearance
| Creatinine clearance | Total daily range | Regimens on the label |
|---|---|---|
| 60 mL/min or higher | 900 to 3600 mg | 300, 400, 600, 800, or 1200 mg three times a day |
| above 30 to 59 mL/min | 400 to 1400 mg | 200, 300, 400, 500, or 700 mg twice a day |
| above 15 to 29 mL/min | 200 to 700 mg | 200, 300, 400, 500, or 700 mg once a day |
| 15 mL/min | 100 to 300 mg | 100, 125, 150, 200, or 300 mg once a day |
| under 15 mL/min | proportional cut | 7.5 mL/min gets half the 15 mL/min daily dose |
Gabapentin is not appreciably metabolized. It leaves in the urine as unchanged drug. Gabapentin elimination half-life is 5 to 7 hours and is unaltered by dose or following multiple dosing. Plasma clearance and renal clearance move with creatinine clearance. When clearance falls, the same 300 mg capsule hangs around longer. In one renal-impairment study, mean half-life ran from about 6.5 hours when creatinine clearance was above 60 mL/min to 52 hours when it was under 30 mL/min.
Dose adjustment in patients 12 years of age and older with renal impairment or undergoing hemodialysis is recommended. In patients with stable renal function, creatinine clearance can be reasonably well estimated using the equation of Cockcroft and Gault. An eGFR printed on a lab slip is a different estimate. Dropping that eGFR into the creatinine-clearance column can select the wrong row. If the chart only shows eGFR, the prescriber has to say which figure the dose was built from.
Read a 300 mg capsule against that table before you copy a three-times-daily habit. Above 30 to 59 mL/min, 300 mg twice a day is one listed regimen. It is 600 mg for the day, inside 400 to 1400 mg. It is not 300 mg three times a day. Above 15 to 29 mL/min, 300 mg once a day is on the row. Three capsules a day are not. At 15 mL/min, 300 mg once daily is the top of the 100 to 300 mg once-daily band. That capsule is the whole day.
Below 15 mL/min, reduce the daily dose in proportion to creatinine clearance. The label's example: a clearance of 7.5 mL/min should receive one-half the daily dose that patients with a creatinine clearance of 15 mL/min receive.
People on hemodialysis keep a maintenance dose from the clearance estimate, then take a supplemental post-hemodialysis dose administered after each 4 hours of hemodialysis. The label lists those supplements as 125, 150, 200, 250, or 350 mg. Gabapentin can be removed by hemodialysis, which is also why overdose care can include dialysis.
Older adults are more likely to have decreased renal function. The label says the dose should be adjusted based on creatinine clearance values in these patients. Age alone is not a 300 mg rule, and a low dose that ignores clearance is how a single capsule becomes a large exposure.
Food, the 12-hour gap, and antacids
When the three-times-daily schedule is the one that fits the clearance, the maximum time between doses should not exceed 12 hours. A missed afternoon dose is not automatically safe to stack at bedtime. The half-life is too short for that kind of catching up, and too long, once the kidneys slow, for casual extra capsules.
Administer Neurontin orally with or without food. Swallow capsules whole with water. If a scored 600 mg or 800 mg tablet is split, the unused half is the next dose. Half-tablets not used within 28 days should be discarded. A 300 mg capsule is not a scored tablet. Do not open it to invent a smaller dose.
An aluminum and magnesium hydroxide antacid, which the label discusses as Maalox, reduced mean gabapentin bioavailability by about 20%. Gabapentin should be taken at least 2 hours after that antacid. A bedtime capsule taken with a bedtime antacid gives away part of the dose.
A 300 mg extended-release title is a different schedule
Gabapentin is not one product on a shelf. Immediate-release capsules, tablets, and solution are not the same schedule as an extended-release tablet, and a veterinary paste is not a human fill. Match the exact product name and release form on the bottle to the prescription before anyone changes a dose.
Another result was a separate DailyMed page for gabapentin 300 mg. This note uses the Neurontin immediate-release label for the table. If your bottle is a different gabapentin product, read that product's label before you borrow these milligrams.
Breathing, driving, and how to stop
Respiratory depression may occur with Neurontin when it is used with other central nervous system depressants, including opioids, or when breathing is already impaired. Slow breathing, lips that look blue, or a person who cannot be woken is emergency care, not a side effect to sleep off. Fatal respiratory depression has been reported with Neurontin overdose, alone and with other depressants. In the United States, poison control is 1-800-222-1222.
The label also warns about somnolence, sedation, and dizziness. Do not drive until you know how the dose affects you.
Stopping has its own clock. If the Neurontin dose is reduced, discontinued, or substituted with an alternative medication, this should be done gradually over a minimum of 1 week. A longer taper may be needed. Antiepileptic drugs should not be stopped abruptly, because seizure frequency can rise. Withdrawal symptoms have been observed after both short and long courses, and suicidal thoughts have been reported after discontinuation. Tell the prescriber you want to stop. A weekend cliff is not the one-week minimum.
Neurontin contains gabapentin, which is not a controlled substance. That sentence is the federal schedule line on this label. This note did not review state lists, so it does not say whether any state tracks gabapentin separately.
What to do with the number you have
Bring the creatinine clearance the dose was calculated from, or ask for it, before you decide that 300 mg three times a day is the normal start. Match the job first: nerve pain after shingles uses the three-day climb toward 1800 mg/day if clearance allows; add-on partial seizures from age 12 use 300 mg three times a day as the start, then 300 to 600 mg three times a day. Then match the kidney row. If those two disagree with the bottle you were handed, the prescriber reconciles them. Pure Health Notes does not sell or dispense gabapentin.
The use map, including what the label does not cover, is on the gabapentin evidence note. The older GABA-name story is on the Neurontin history note. Handling on the medicine page sits at Neurontin. The table above was read from the Neurontin label on DailyMed.
Reviewed against the Neurontin prescribing information on DailyMed on 24 October 2026.