01 Section
A 400 mg shell on a daylight shelf
Four hundred milligrams sits on this shelf as a counted capsule, not as a finished day. Neurontin and its generics ship 100 mg, 300 mg, and 400 mg shells. The 600 mg and 800 mg pieces are tablets. People type 'nerve pain' and land on 400 mg because that is the capsule they can see. The label's PHN climb does not start there.
Day 1 of labelled postherpetic neuralgia is a single 300 mg swallow. Day 2 is 600 mg split twice. Day 3 is 900 mg in three pieces. The dose can then rise, if pain still needs it, to 1800 mg a day as 600 mg three times daily. Trials looked from 1800 mg to 3600 mg and did not show extra benefit past 1800 mg. A 400 mg twice-daily month is 800 mg. That is a rung. It is not the studied PHN finish.
I lock this note to 400 mg so the title, the H1, and the three descriptions stay on one labelled option. The body may name the rest of the ladder. Search should not pretend every gabapentin page on the internet is a 300 mg start. Dr. Ingrid Sørensen peer-passes the draft against DailyMed. Corrections can reach [email protected].
Swallow the capsule whole with water. Food is optional on the Neurontin line. An aluminum-magnesium antacid cut mean bioavailability by about 20% in the interaction work. Wait at least two hours after that antacid before the next gabapentin dose. Gralise and Horizant are different products with different food rules. Do not swap them on a blog's say-so.
02 Section
Creatinine clearance rewrites the capsule count
Kidneys set the ceiling before any 400 mg habit should feel permanent. The label adjusts from age 12 when filtration is reduced. The ≥60 mL/min row runs 900 mg to 3600 mg a day in three splits. The next row, above 30 to 59, runs 400 mg to 1400 mg in two splits. Above 15 to 29 is a once-daily 200 mg to 700 mg band. At 15 mL/min the day shrinks to 100 mg to 300 mg. Hemodialysis adds a post-dialysis supplement.
A 400 mg twice-daily lock on a person whose clearance is 25 is already off that table. I will not 'try it and see' when the number is printed. Cockcroft-Gault is the estimate the label names when a measured clearance is not sitting in the chart. Ask for the number. A normal serum creatinine in an older, smaller body can still hide a 40 mL/min clearance.
Morphine raised gabapentin levels in the interaction work. Cimetidine nudged clearance down a little; the label did not call that change clinically important. The antacid rule above still stands. None of those notes replace a pharmacist who can see the whole list. Bring the box, not a memory of the box.
Elderly dose selection should start low. That is label language, not courtesy. Peripheral edema and ataxia were more common with age in the PHN set. A 400 mg capsule that looked modest on a coupon page can be a heavy day in a person whose filtration has drifted. Recheck the labs when the dose has been stable for a while, not only on day one.
03 Section
Why a backache is a different letter than PHN
Ordinary lumbar ache is a different letter than a shingles stripe. Muscle, facet, and disc pain run on tissue signals. Gabapentin was not built for that. Mayo's consumer page says the same thing in plainer words: this medicine is not for routine pain from a minor injury or from arthritis. I agree with that line, and I say it in clinic before anyone leaves with a 400 mg box 'just to try.'
Reviews that pooled anticonvulsants against placebo in chronic low back pain and in lumbar radicular pain found little or no useful effect and more adverse events. CMAJ in 2018 called that evidence moderate to high for the lack of benefit. A separate gabapentinoid review in chronic low back pain saw no meaningful change on a 0-to-10 scale and more dizziness, fatigue, and visual blur. NICE does not put these drugs on the ordinary chronic-back-pain path.
Sciatica sits in a grey band. UK neuropathic-pain guidance has allowed gabapentinoids for some nerve-root pictures, and then the radicular trials came back thin. If the pain shoots, burns, or sparks, I will still examine the nerve story. I will not open a 400 mg capsule because a friend 'fixed his back' on it. That sentence has sent too many people into fog for a mechanical problem.
Off-label writing is not a crime. It is a documented choice. The honest version names the indication that is missing, names the review that failed, and names the side-effect cost. If your prescriber still chooses gabapentin for a mixed picture, ask them which part of the pain they think is neuropathic. If they cannot point to a nerve signature, the 400 mg lock on this shelf is the wrong card.
04 Section
Price notes without a invented board, then the week you come down
What I say at the counter and at the stop
- Ask the window to price the 400 mg count on the script, often sixty for a twice-daily month.
- A ninety-count coupon board is a different NDC conversation.
- Brand Neurontin and generic gabapentin 400 mg are the same molecule, not the same invoice.
- Reduce or stop over at least one week. Longer if the prescriber draws it that way.
- Do not drop a steady dose because a page felt finished.
Coupon boards list ninety capsules more often than they list sixty. This shelf's 400 mg lock, if the script is twice daily for a month, is a sixty-count. I will not print a dollar here. ZIP, insurance, and the week you stand at the window move the number. Ask the pharmacist to price the count on the script. Brand Neurontin and a generic 400 mg capsule are the same molecule and are not the same invoice.
A ninety-count coupon on a different NDC is a different conversation. So is a 300 mg shell. So is a 600 mg scored tablet. If someone quotes a board from a comparison site, keep that quote in the caption of a sourced window, not as a promise this page can honour. Bellis does not dispense. The gabapentin medicine note is where a dated cash window lives when we have one. This guide will not invent a neighbour's price.
Stopping is not the inverse of a coupon. If the dose is reduced, stopped, or swapped, the label wants a gradual change over a minimum of one week. A longer taper is the prescriber's call. Abrupt interruption in a person with seizures can raise seizure frequency. People without epilepsy still report malaise, sweats, and a rebound of the original burn when they drop a steady dose overnight.
I do not publish a home-made 400 mg step-down on this page. A week is the floor, not a recipe. If you have been on a high day-count for months, expect the descent to be drawn in clinic, not in a search result. Write the shelf at [email protected] if a line here is stale. Do not write your own taper to that address and wait for a blessing.
05 Section
What usually arrives before the burning eases
Sleepiness shows up in the first week more often than a quiet night does. Dizziness, ataxia, and peripheral edema sit on the same short list. The label warns people not to drive until they know how the capsule treats them. I repeat that in daylight words: do not test a new 400 mg swallow on a motorway commute.
Antiepileptic drugs as a class, gabapentin included, raise the risk of suicidal thinking or behavior. Pooled placebo trials put the rate at 0.43% on drug and 0.24% on placebo, about one extra case per 530 people treated, with an adjusted relative risk of 1.8. The signal showed up as early as one week. Families should hear that before the first box, not after a mood change is already loud.
Respiratory depression is on the label when gabapentin sits next to an opioid or another CNS depressant, or when the lungs are already impaired. Case reports include deaths. If both medicines are truly needed, the start should be low and watched. A 400 mg capsule plus a regular oxycodone is not a casual pair. Tell the person who wrote each script.
Give a climb a few weeks before you call it useless. The PHN schedule spends three days just getting to 900 mg. A person who stops on day four because 'nothing happened' stopped on a loading ramp. What I ask is whether the burn is quieter and sleep is possible, not whether the pain has vanished. If you have reached a fair dose and feel nothing but fog, that is a reason to taper, not a reason to stay out of loyalty.
06 Section
The pain the US label actually names
What this 400 mg note is holding
Shingles can leave a stripe of burning after the rash has gone. That leftover pain, lasting more than three months after the skin heals in the trials, is postherpetic neuralgia. Neurontin is indicated for that job in adults. It is also adjunctive therapy for partial-onset seizures from age three. Those two lines are what the US label signed. Everything else is a clinic decision written beside the label, not on it.
Controlled PHN work on Neurontin treated 336 adults. About 30% were 65 to 74. Half were 75 or older. The older group looked as if they got more effect at the same milligram count. Gabapentin leaves the body through the kidney as unchanged drug. Age often means less clearance, which means more drug for the same capsule. That is a reason to respect creatinine, not a reason to chase a higher board on your own.
Diabetic burning in the feet is a nerve signature many of us still treat with gabapentin. Cochrane-level reviews of neuropathic pain found moderate support at 1800 mg to 3600 mg a day in PHN and in diabetic neuropathy. The second of those uses remains off-label for Neurontin in the United States. I will write it when the pain is neuropathic and the kidneys allow it. I will not dress it up as an FDA pain line.
The molecule does not sit on a GABA receptor, despite the name. It binds the alpha-2-delta subunit of voltage-gated calcium channels and quiets an over-firing sensory line. Ibuprofen does not do that job. That is why a person can take a tissue painkiller around the clock and still feel the sheet as fire. It is also why a mechanical backache is a poor target. Wrong wiring problem. Wrong letter.
07 Section
How 400 mg twice daily sits on the climb
| What you are holding | Day total | Where it sits |
|---|---|---|
| 400 mg twice daily (this lock) | 800 mg | A mid-climb pause, or a renal-row dose |
| 400 mg three times daily | 1200 mg | Printed on the ≥60 mL/min row |
| 600 mg three times daily | 1800 mg | Labelled PHN target if pain still needs it |
| Above 1800 mg | Up to 3600 mg in trials | No extra PHN benefit shown past 1800 |
Climbing toward eighteen hundred milligrams a day is the PHN story the label tells. A person who stays on 400 mg in the morning and 400 mg at night is on 800 mg. That can be a fair pause if dizziness is loud, if the kidneys are not the ≥60 row, or if a prescriber is still watching the first fortnight. It is a poor place to declare the drug a failure.
Bioavailability falls as the day-count rises. About 60% at 900 mg a day. About 47% at 1200 mg. About 34% at 2400 mg. The gut does not absorb a bigger swallow as efficiently as a smaller one. That is one reason the label splits the day and keeps the longest gap at or under 12 hours on a three-times schedule. A single 400 mg souvenir in the evening does not mimic the PHN trials.
On the renal table, 400 mg twice daily is a printed option when creatinine clearance sits above 30 and at or under 59 mL/min, inside a 400 mg to 1400 mg day. When clearance is 60 or higher, 400 mg three times daily is a listed 1200 mg regimen. Same capsule. Different kidneys. The full gabapentin note keeps the whole grid. This page will not pretend one 400 mg lock fits every filtration rate.
Half-life in people with decent clearance is 5 to 7 hours. In a 400 mg single-dose study, mean half-life stretched from about 6.5 hours when clearance was above 60 mL/min to about 52 hours when it was under 30. That is why an older person on a 'modest' 400 mg twice-daily plan can look more sedated than a younger person on 600 mg three times a day. The capsule is the same. The clearance is not.
08 Section
Take the 400 mg question back to the person who wrote it
Bring the 400 mg question back to the clinician who can see the rash date, the nerve exam, the creatinine, and the other sedating drugs. A daylight note can hold a lock. It cannot examine you. If the pain is a shingles leftover, the label has a climb. If the pain is a weekend backache, this capsule is a weak answer dressed in a strong reputation.
Dr. Ingrid Sørensen signs the peer-pass on this shelf. The longer renal table, the seizure adjunct, and the interaction list sit on the gabapentin medicine page. For a public-language companion that is not ours, MedlinePlus on gabapentin stays useful. Nothing here fills a bottle or replaces the person who wrote the script.