Neurontin 800 mg sits on a CrCl step, not a start

01800 mg three times a day is a high-step, not a first blister

Epilepsy maintenance on the PI is 300 to 600 mg three times a day. Tablets of 600 mg and 800 mg exist so those divided doses can be built. 800 mg three times a day is 2400 mg daily. That is a tolerated long-term figure in epilepsy studies, not a day-one PHN start.

Postherpetic neuralgia starts at 300 mg on day one, 600 on day two, 900 on day three, then often 1800 mg daily. Trials showed effect from 1800 to 3600 mg daily with comparable effect across that span; extra benefit above 1800 was not shown in those studies.

People arrive at the desk with an 800 mg pack because 'the pain is bad.' Pain intensity does not rewrite creatinine clearance. If CrCl has drifted under 60, that 800 mg TID row is the wrong row.

02Hemodialysis days use a different arithmetic

Anuric adults in a small study had an apparent half-life around 132 hours on nondialysis days, falling to about 3.8 hours during dialysis. The label therefore adds a supplemental post-hemodialysis dose after each four hours of dialysis, on top of a maintenance dose drawn from the CrCl estimate.

Supplemental examples on the table run 125, 150, 200, 250, or 350 mg. Those are not 800 mg tablets. Do not 'use the big tablet because dialysis is hard.'

Missing a supplemental dose and then doubling an 800 mg tablet at home is how a somnolent Sunday starts. Call the dialysis unit's pharmacist.

03The twelve-hour epilepsy gap is not a renal override

For epilepsy, the PI says the maximum time between doses should not exceed twelve hours. People who 'save' an 800 mg tablet for a later pain flare break that rhythm and then double up. That is two errors.

A renal redesign may move a person from TID to BID or once daily. That new rhythm still needs an explicit clock. Do not keep swallowing 800 mg every eight hours on a CrCl band that no longer lists TID.

If seizures cluster after a missed taper, that is urgent care, not a reason to restart 800 mg TID from a year-old pack. Bring the last creatinine with you.

Pediatric patients under 12 with reduced kidney function were not studied for these adult steps. Do not scale an 800 mg tablet by a child's weight at home.

04PHN day-one 300 mg is not an 800 mg story

Postherpetic neuralgia on the PI starts at 300 mg on day one, 600 on day two, and 900 on day three, then often 1800 mg daily. Jumping to an 800 mg tablet on night one because the zoster pain is loud skips that ramp and skips the kidney check.

Trials in that indication showed effect from 1800 to 3600 mg daily with comparable effect across the span. Extra benefit above 1800 was not demonstrated there. A high-step tablet is not automatically a better pain tablet.

If someone already sits on 800 mg TID for epilepsy, a new PHN flare is not a reason to add a fourth 800. Redesign the total daily milligrams against CrCl instead.

05Weight, age, and the Cockcroft-Gault scrap

The label names Cockcroft-Gault when a measured clearance is missing. That equation wants age, weight, sex, and serum creatinine. A portal eGFR without those inputs is a prompt, not a finished step.

A ten-kilogram weight loss after illness changes the estimate even if the creatinine looks 'about the same.' Bring the weight that was used last time, not a remembered one.

Older adults accumulate gabapentin when the kidney slows. An 800 mg blister filled at sixty-five can be the wrong step at seventy-eight after an AKI. Recalculate before the next pack, not after a fall.

06When the last creatinine is older than the blister

Bring the date of the last creatinine, the weight used in Cockcroft-Gault, and the current tablet strength. If the lab is a year old and the person is 78, that is the visit, not a refill argument.

Ataxia, new somnolence, or myoclonus after a stable 800 mg plan is a reason to think accumulation, not a reason to add an opioid 'for breakthrough.' Read the sedation-stack despatch.

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07Older eGFR drift and the 800 mg tablet in the drawer

Half-life in a 400 mg single-dose renal study ran about 6.5 hours when CrCl was above 60 and about 52 hours when CrCl was under 30. Parent clearance tracked the kidney. There is no hepatic rescue path that saves an 800 mg habit when creatinine climbs.

A blister filled a year ago at 800 mg TID can be wrong after an AKI, an ACE-inhibitor start, or a lost ten kilograms. Recalculate. Do not wait for a fall.

Pediatric renal impairment under 12 was not studied for these adjustments. Do not scale an adult 800 mg tablet by weight at home.

08Absorption falls as the daily total climbs

Gabapentin bioavailability is not proportional to dose. The PI cites about 60 percent at 900 mg/day, 47 at 1200, 34 at 2400, 33 at 3600, and 27 at 4800, each in three divided doses. More milligrams in the bottle do not mean a linear rise in absorbed drug.

That is one reason 800 mg TID can disappoint as a 'stronger' pain move if the person never absorbed the last step cleanly. It is also why stacking extra tablets at night is a poor answer to a missed noon dose.

Food only nudges AUC and Cmax up about 14 percent. A meal is not a renal adjustment.

09A meal is not a renal adjustment and neither is a missed noon dose

Food only nudges gabapentin AUC and Cmax up about 14 percent. That is not a Cockcroft-Gault change and not a reason to keep an 800 mg TID plan when CrCl has fallen.

Missed noon doses tempt a double evening swallow. Bioavailability already falls as daily totals climb - about 34 percent at 2400 mg/day in three divided doses on the PI. Stacking two 800s at night is a poor answer to a missed midday tablet.

If ataxia or new somnolence appears on a 'stable' 800 mg plan, think accumulation and a new creatinine, not an extra opioid for breakthrough. The sedation-stack despatch is the next door, not a gym-bag hydrocodone.

Write the last lab date on the blister card. A pack that outlives its creatinine is the usual letter we get after a fall.

Hemodialysis removes gabapentin; the anuric half-life on a nondialysis day in the cited study sat near 132 hours and fell to about 3.8 hours during dialysis. That is why the supplemental dose is small and timed after a four-hour run, not another 800 mg 'because dialysis is hard.'

Seizure patients who stop for a rising creatinine still need a taper plan. A renal hold is not an abrupt psychiatric-style washout. Bring the epilepsy indication to the same visit as the new CrCl.

10Creatinine clearance before the next 800 mg pack

CrCl at or above 60 mL/min: total daily 900 to 3600 mg, with example regimens that include 300, 400, 600, 800, or 1200 mg three times a day.

CrCl above 30 to 59: 400 to 1400 mg daily, given twice a day. CrCl above 15 to 29: 200 to 700 mg once daily. At 15 mL/min: 100 to 300 mg once daily. Below 15, reduce in proportion (the PI's example: 7.5 mL/min gets half the 15 mL/min daily dose).

Cockcroft-Gault is the outpatient estimate the label names when a measured clearance is not sitting on the chart. An eGFR from a lab portal is not automatically the same number. Ask which equation the clinic used.

11Abrupt stop still risks more seizures

If gabapentin is treating seizures, a sudden stop can raise seizure frequency. Taper with the prescriber even when the reason for the stop is a climbing creatinine.

A renal hold is not the same as a psychiatric washout. Do not copy fluoxetine's five-week grammar onto Neurontin.

Maximum gap between epilepsy doses should not exceed twelve hours on the labeled schedule. That rule does not override a renal redesign. It explains why people feel unstable when they 'save tablets' for later.

12Seal on the renal-step card

Treat 800 mg as a high-step tablet. Recalculate CrCl before the next pack. Dialysis extras are small supplemental milligrams, not another 800.

Return to the gabapentin letter for indication-specific starts. This postscript is the kidney ladder.

Portal eGFR is a prompt. Cockcroft-Gault wants age, weight, sex, and creatinine. Bring the weight that was used last time if it changed.