Gabapentin (brand name “Neurontin”) is a drug initially approved by the FDA in 1993 as an adjunct treatment for partial seizures, and 11 years later in 2004, received approval for the treatment of neuropathic pain.  It has since gained popularity as an off-label treatment for a variety of conditions including: anxiety disorders, bipolar disorder, hot flashes, insomnia, and restless leg syndrome.  A surge in off-label popularity and recreational use of gabapentin may have been a result of an unethical marketing campaign initiated by Pfizer in the late 1990s/early 2000s.

The drug is considered a lipophilic structural analogue of the neurotransmitter GABA (gamma-aminobutyric acid).  Although its mechanism of action isn’t fully elucidated, it is speculated to modulate enzymes glutamate decarboxylase (GAD) and branched chain aminotransferase (BCAT).  Modulation of glutamate decarboxylase is thought to enhance GABA synthesis, whereas modulation of branched chain aminotransferase is thought to affect glutamate.

As a result of its enzymatic modulation to facilitate increases in extracellular GABA, users often experience increased relaxation (mentally and physically), decreases in pain, and enhanced well-being.  Though the benefits may sound appealing, its inhibitory effects may: impair concentration (causing brain fog), compromise work/school performance, and interfere with learning/memory.  For this reason, many individuals have decided to stop taking gabapentin and hope to clear it from their system.

How long does Gabapentin stay in your system after stopping? (Neurontin)

If you’ve stopped taking this drug, you may notice a swift onset of disconcerting gabapentin withdrawal symptoms.  As a result of these harsh discontinuation effects, you’re probably wondering whether how long it’ll take to fully excrete the drug from your body.  To determine the average amount of time it takes to excrete gabapentin, it is necessary to consider its half-life within the range of 5 to 7 hours.

This indicates that after you’ve taken a gabapentin dose, approximately 50% will have been cleared from your system within 5 to 7 hours (on average).  Using this information, we can determine that gabapentin will stay in your system for an estimated 1.15 to 1.60 days after your final dose.  In other words, you shouldn’t expect any of the gabapentin to remain in systemic circulation after 2 days (48 hours) post-ingestion.

Unless an individual exhibits impaired renal (kidney) function, it shouldn’t take more than 2 days to excrete the drug.  Furthermore, gabapentin differs from many other substances in that it is not broken down via liver enzymes to form metabolites.  Therefore, you won’t need to worry about metabolites lingering for longer than the parent compound (gabapentin).

  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/gabapentin

Variables that influence how long Gabapentin stays in your system

Despite the fact that gabapentin is likely to stay in a person’s system for 1 to 2 days after discontinuation, some people will excrete the drug quicker than others.  The differences in excretion speed are usually a result of variables such as: renal function, the individual taking gabapentin, dosage administered, and term of administration.

  1. Renal function

Individuals with normative renal function shouldn’t have difficulties excreting gabapentin within 2 days of their last dose.  However, individuals with renal impairment experience higher plasma concentrations of gabapentin, as well as an increased elimination half-life.  For example, one report documented that among 11 individuals with renal failure, just one 400 mg oral gabapentin dose had a half-life of 132 hours (on average).

Should you have renal failure and take just one dose of gabapentin, it could take over 30 days for complete systemic excretion.  A general rule of thumb to keep in mind is that the elimination half-life of gabapentin is influenced directly by the severity of renal impairment.  The poorer your kidney function, the longer it’ll take to eliminate the drug from your system.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/8062491

  1. Individual factors

Two individuals with healthy renal function could simultaneously administer a single dose of gabapentin (100 mg), yet one person may excrete the drug at a faster pace than the other.  Individual factors such as a person’s age, body mass, hydration, and urinary pH could affect excretion speed of gabapentin.

Age: In most cases, elderly individuals (age 65+) are thought to excrete gabapentin at a slower rate than those who are younger.  Slower excretion among the elderly may be a result of impaired or declining renal function associated with old age.  Often times as a person gets older, their kidney function is no longer as efficient as when they were young.

Younger adults and adolescents are likely to excrete gabapentin with efficiency as a result of their healthy kidney function.  Furthermore, the entire physiology of a younger individual is operating with greater efficiency – they aren’t experiencing age-related decline.  In old age, physiologic function and efficiency continues to diminish, resulting in greater accumulation of gabapentin prior to excretion.

Body mass + fat: The size of an individual (relative to dosing) may affect how quickly they’re able to excrete gabapentin.  A tall/heavy individual taking 100 mg of gabapentin is likely to excrete it with greater efficiency than a small/light person taking the same dose.  This is due to the fact that in the case of the less massive individual, there’s a greater amount of drug in their system relative to its overall size – making it tougher to excrete.

Some also speculate that as a result of its hydrophilic properties, gabapentin may accumulate to a greater extent among individuals with low body fat and high muscle composition.  On the other hand, those with high body fat may excrete the drug quicker due to the fact that fat reduces water retention.  Therefore, the greater percentage your body fat – the faster you’ll likely excrete gabapentin.

Hydration: It is understood that gabapentin is processed by the kidneys and excreted 100% unchanged in urine.  Since it is eliminated via urine, the degree to which a person is hydrated could have a subtle effect on its clearance speed.  Clearance speed of drugs is influenced by urinary flow rate, which in turn is affected by hydration.

The more hydrated a person is, the greater their urinary flow rate.  The less hydrated an individual, the lesser their urinary flow rate.  Urinary flow rate is known to influence clearance speed of drugs – with increased urinary flow being associated with greater clearance.  Therefore, the more hydrated you are, the quicker you may clear gabapentin from your system.

Urinary pH: The pH of your urine may have an impact on how quickly gabapentin is excreted from your body.  It is understood that urine of high alkalinity (high pH urine) is associated with slower clearance speed of various drugs.  Alkaline urine promotes reabsorption and recirculation prior to systemic excretion, thereby leading to an increased elimination half-life of substances.

On the other hand, acidic urine (low pH urine) is associated with faster clearance of drugs.  If you’re eating a diet high in acidic foods, you may excrete gabapentin faster than someone eating a highly alkaline diet.  Acidification of urine inhibits reabsorption and maximizes clearance speed.

  1. Dosage (300 mg to 3600 mg)

The greater the dosage of gabapentin you take, the longer it may stay in your system.  High dosages place a greater burden on the kidneys prior to excretion, resulting in a longer elimination half-life.  In addition, when you take a high dose, a greater quantity of the drug (an exogenous chemical) will circulate throughout your body.

An increased amount of circulating gabapentin translates to a greater level of accumulation prior to elimination.  Furthermore, when your body attempts to excrete high doses of gabapentin via the kidneys, the efficiency of excretion will be compromised.  This is due to the fact that the kidneys are only capable of efficiently excreting a set amount of the drug at a time.

Conversely, when administered at lower doses, there’s a decreased amount of gabapentin distribution and accumulation throughout the body.  Additionally, low doses are thought to be excreted with greater efficiency by the kidneys.  For this reason, individuals with renal (kidney) impairment are often given lower-than-average doses.

  1. Term of administration (Acute vs. Chronic)

The duration over which you’ve been taking gabapentin may affect how long it stays in your system before elimination.  Duration of administration is thought to influence: dosing, physiology, and accumulation of the drug in a person’s system.  Long-term administration of gabapentin is associated with neurophysiological tolerance to low doses; hence higher doses are often administered.

As a result of these upward titrations in dosing, a greater total amount of gabapentin needs to be excreted by the kidneys each day.  The increase in dosing places a greater burden on the kidneys, resulting in less efficient clearance – ultimately prolonging renal excretion.  When administered over a short-term, gabapentin is likely to be taken at lower doses and get excreted with greater efficiency.

Gabapentin (Neurontin): Absorption, Distribution, Excretion

Following oral administration of gabapentin, it is rapidly absorbed from the proximal small bowel and distributed throughout the bloodstream via the saturable L-amino acid transporter.  The limited capacity of the L-amino acid transport system facilitates a dose-dependent bioavailability of gabapentin.  Bioavailability of gabapentin is considered around 60% at doses up to 900 mg, whereas additional quantities above 900 mg are only 10-35% bioavailable.

At a dose of 4800 mg per day, bioavailability will have decreased to just 27%.  Taking gabapentin with food is thought to have a modest effect on its absorption, increasing its area under the curve (AUC) by ~14%.  Unlike may psychiatric drugs, gabapentin is not subject to hepatic metabolism and less than 3% of a dose binds to plasma proteins.

Concentrations of gabapentin are thought to peak between 2 to 4 hours after administration.  The drug is distributed at a volume of 50-60 L and effectively penetrates the blood-brain barrier.  Once the drug has been absorbed and distributed, it is processed by the kidneys prior to excretion.

Among those with normative kidney function, gabapentin is excreted at 190 mL/min and carries a 5 to 7 hour half-life.  Since it is not metabolized within the liver, no metabolites are formed prior to excretion.  As a result, the entire drug is typically excreted in unchanged form, within 2 days of cessation.

  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/gabapentin
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/8022536

How to get gabapentin out of your system

If you’ve ceased taking gabapentin, you probably want to eliminate it from your body as quickly as possible.  The good news is that your body is more than capable of detoxifying itself and purging exogenous substances.  Below are some tips for maximizing the efficiency by which gabapentin is excreted from your body.  Prior to implementing any of these suggestions, always consult a medical professional to verify their safety and alleged efficacy.

  1. Complete cessation: Really the best way to ensure that gabapentin will leave your body is to stop taking it. Like any other drug, the sooner you stop taking it, the quicker you can expect to be fully detoxified. If you continue using the drug, you shouldn’t expect to eliminate it from your system.
  2. Hydration: Maintaining adequate hydration is necessary for optimal renal function. Staying hydrated also is known to increase urinary flow rate, which in turn expedites drug clearance. Though there isn’t any research on urinary flow rate and gabapentin excretion speed, it is likely that a well-hydrated person would excrete the drug quicker than someone who’s dehydrated.
  3. Dietary acidification: It could be theorized that increasing consumption of acidic foods may decrease the time gabapentin stays in your system. Acidic foods lower the pH of your urine, which prevents reabsorption and recirculation of drugs prior to renal excretion. If you have a high urinary pH, eating more acidic foods could decrease the elimination half-life of gabapentin.  Keep in mind that acidification shouldn’t be done in excess as this could cause acidosis.

How long has Gabapentin stayed in your system after stopping?

If you’ve stopped taking Gabapentin, mention how long you believe it stayed in your system in the comments section below.  Discuss various factors that may have influenced its elimination half-life in your body such as: renal function, your age, dosage ingested, and term/frequency of administration.  Realize that unless you have renal impairment or insufficiency, you’ll likely have fully excreted gabapentin from your system in under 2 days.

There’s no reason to suspect that gabapentin will linger in your body in excess of 48 hours following your final dose.  The drug is highly hydrophilic, doesn’t form metabolites, and certainly doesn’t accumulate within bodily tissues. If you suspect that other factors may affect clearance and/or elimination half-life of gabapentin, share them in your comment.