How this instrument works
Gabapentin is FDA-labeled as an adjunct (add-on) therapy for partial seizures in children ages 3 to 11, dosed by weight and divided into three doses a day (TID). Treatment starts at a lower dose and is titrated upward over roughly three days to a higher target dose, rather than starting at the target dose immediately.
The starting dose is 10-15 mg/kg/day (this calculator uses the 12.5 mg/kg/day midpoint), divided into three doses. The target dose depends on age: for ages 3-4, the target is 40 mg/kg/day; for ages 5-11, the target is 25-35 mg/kg/day (this calculator uses the 30 mg/kg/day midpoint) — both also divided into three doses. The higher target for younger children (3-4) reflects faster gabapentin clearance at that age, which the FDA label accounts for with a separate, higher target rate.
This calculator is scoped narrowly to that pediatric seizure-adjunct indication, ages 3 through 11. It does NOT cover ages 12 and up, who move to a fixed, non-weight-based adult titration schedule under the FDA label rather than this weight-based formula, and it does NOT cover adult dosing for other indications gabapentin is used for, such as neuropathic pain or postherpetic neuralgia, where dosing is individualized well beyond a simple weight-based calculation. Use this only as a reference to confirm against a prescription written by the child's neurologist or pediatrician — never to start or adjust a seizure medication on your own.
- Enter the child's weight in kilograms.
- Enter the child's age in years (this calculator covers ages 3-11 only).
- Read the starting daily dose in mg/day and the amount per dose, divided three times a day (TID).
- Read the titrated target daily dose and per-dose amount, reached over about 3 days per the prescriber's schedule.
Worked example — 20 kg, 6-year-old
A 20 kg, 6-year-old starts at 20 × 12.5 = 250 mg/day, divided into three doses of about 83.3 mg each. Because this child is in the 5-11 age band, the target rate is 30 mg/kg/day, giving a titrated target of 20 × 30 = 600 mg/day, or 200 mg per dose, three times a day — reached over about three days of titration per the prescriber's plan.
For comparison, a 16 kg, 4-year-old — in the higher-target 3-4 age band — starts at 16 × 12.5 = 200 mg/day (about 66.7 mg per dose) but titrates to a noticeably higher target of 16 × 40 = 640 mg/day (213.3 mg per dose), because the 40 mg/kg/day rate for ages 3-4 exceeds the 30 mg/kg/day rate used for ages 5-11 even though this child weighs less.
Questions
Is this calculator a substitute for the prescribing clinician's dosing plan?
No. Gabapentin dosing and titration speed for a child with seizures should always follow the specific plan set by the prescribing neurologist or pediatrician, who accounts for seizure type, response, kidney function, and other medications. Use this only to sanity-check the arithmetic behind a prescription, and raise any discrepancy with the prescriber rather than adjusting the dose yourself.
Why does the target dose depend on the child's age?
Younger children (ages 3-4) tend to clear gabapentin from the body faster than older children, and the FDA label accounts for this with a higher target rate — 40 mg/kg/day for ages 3-4, versus 25-35 mg/kg/day for ages 5-11 — so that a younger child reaches an effective drug level despite faster clearance.
Why does dosing start lower and increase over several days instead of starting at the target dose?
Titrating upward over about three days lets the child's body adjust gradually, which tends to reduce dose-related side effects like drowsiness or unsteadiness compared to starting directly at the target dose. The exact titration schedule and pace should follow the prescriber's specific plan.
Does this calculator apply to a 12-year-old or a teenager?
No. This calculator is scoped to ages 3-11 only, per the FDA pediatric partial-seizure labeling. Patients 12 and older move to a different, fixed, non-weight-based adult titration schedule instead — plugging a 12-year-old's weight into this calculator's formula would not reflect the actual labeled dosing for that age group.
Can this calculator be used for gabapentin prescribed for pain instead of seizures?
No. This calculator reflects only the pediatric seizure-adjunct dosing schedule. Gabapentin prescribed for neuropathic pain, postherpetic neuralgia, or other off-label pediatric or adult uses follows different, individualized dosing that this calculator does not model.
Is gabapentin ever used alone for seizures in children this age?
The FDA pediatric labeling for ages 3-11 covers gabapentin as adjunct (add-on) therapy alongside another antiseizure medication, not as a standalone first-line treatment. Whether it's used alone in a particular case is a decision for the treating neurologist based on the child's specific seizure type and history.
What should I do if a dose is missed?
Follow the specific instructions given by the prescriber or pharmacist for that child's regimen, since missed-dose guidance can depend on how close it is to the next scheduled dose and the seizure type being treated. Don't double up a dose without checking first — call the prescribing clinician or pharmacist for guidance.
References
- FDA — Neurontin (gabapentin) Prescribing Information (DailyMed)
- Yasaei R, Katta S, Patel P, Saadabadi A — Gabapentin, StatPearls [Internet]
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.