Identification, Side Effects, and Half-Life of Gabapentin

Gabapentin is among the most commonly prescribed medications in the United States. It has various uses, including the relief of nerve pain, anxiety, restless leg syndrome, and post-traumatic stress disorder (PTSD). This medication is short-acting, with an elimination half-life of five to seven hours, though this duration can vary for individuals with certain chronic health conditions.

In this guide, you’ll learn about gabapentin, including how it works, its side effects, and the factors that influence its elimination half-life. Additionally, we will discuss the issues of dependence, addiction, and withdrawal associated with gabapentin.

What is Gabapentin?

Gabapentin is an anticonvulsant medication that was originally introduced in 1993 as a muscle relaxant and antispasmodic.[1] However, despite its initial purpose, it is now widely recognized as an effective treatment for seizures and nerve pain. Some physicians also prescribe gabapentin off-label for specific psychiatric disorders, making it a versatile option in the pharmaceutical industry. 

FDA-Approved Uses and Off-Label Indications

Gabapentin is FDA-approved for use in individuals aged three and older for the treatment of:[1]

• Epilepsy (to be used along with other antiepileptic drugs)
• Postherpetic neuralgia 
• Moderate-to-severe restless leg syndrome (RLS)

There are also several off-label uses, which include:[1]

• Resistant depression
• Bipolar disorder
• Anxiety disorders
• Mood disorders
• Irritable bowel syndrome
• Alcohol withdrawal
• Postoperative neuropathy
• Social phobia
• Generalized tonic-clonic seizures
• Pruritus
• Insomnia
• Post Traumatic stress disorder (PTSD)
• Refractory chronic cough
• Postmenopausal vasomotor symptoms 

Mechanism of Action 

Gabapentin interacts with GABA receptors in the central nervous system (CNS), although the exact nature of this interaction is still not fully understood.[1] Researchers have discovered that gabapentin has the ability to breach the blood-brain barrier, allowing it to act on and mimic naturally occurring neurotransmitters. 

Pharmacokinetics

This medication is not completely absorbed in the body. In fact, gabapentin’s bioavailability varies based on the dose and other factors. 

The absorption percentages are as follows:[1]

• 900 mg: 60%
• 1200 mg: 47%
• 2400 mg: 34%
• 3600 mg: 33%
• 4800 mg: 27%

Transportation methods seem to have the greatest impact on the bioavailability of gabapentin doses. 

Dosage and Route of Administration 

Gabapentin is available in two forms: gabapentin and gabapentin enacarbil.[1] Standard gabapentin comes in tablet, oral solution, and capsule forms. Gabapentin tablets are offered in strengths of 600 mg and 800 mg. Capsules are available in strengths of 100 mg, 300 mg, and 400 mg. The oral solution is available at a strength of 250 mg/5 ml. Gabapentin enacarbil is available as a 300 mg extended-release formulation tablet. 

Standard dosing schedules are as follows:[1]

• Fibromyalgia: 400 to 800 mg taken orally three times daily.
• Restless leg syndrome (RLS): 600 mg taken orally once daily. 
• Neuropathic pain: 300 to 1200 mg taken orally three times daily. 
• Partial seizures: 300 to 1200 mg taken orally three times daily. 
• Patients with renal impairment: between 100 and 700 mg once daily (depending on creatinine clearance rate). 

What is the Elimination Half-Life of Gabapentin?

Gabapentin’s elimination half-life ranges from five to seven hours.[2] This duration represents the time it takes for 50% of its concentration to leave the body.[3] Notably, this timeframe remains consistent regardless of the condition it is prescribed to treat. Nonetheless, various factors can influence the overall elimination time of the drug. As a general guideline, the total elimination time for any drug is typically four to five half-lives.[4]

What Factors Influence Gabapentin’s Half-Life?

Typically, a drug is 90% cleared from the body after 3.3 half-lives, with complete elimination occurring within four to five half-lives.[4] However, this duration can vary in certain circumstances. The Journal of Clinical and Practical Psychopharmacology indicates that a drug’s half-life is affected by its distribution, metabolism, and excretion.[5] These factors are further influenced by age, simultaneous use of other medications, and the existence of liver or kidney disease. 

Researchers discovered that patients with renal disease who received gabapentin as pain relief experienced toxic serum levels within the expected elimination half-life.[6] This issue stemmed from their reduced ability to metabolize the drug, given that its main elimination pathway is via the kidneys. While a general guideline for healthy individuals suggests 90% excretion after 3.3 elimination half-lives, this does not apply to those with chronic kidney disease.[6]

Will I Experience Side Effects When Taking Gabapentin?

Gabapentin, also known by its brand name, Neurontin, is associated with several commonly experienced side effects.[7] Though they are usually mild, some people find them bothersome enough to switch to other medications.

The most common side effects are as follows:[7]

• Dry mouth
• Drowsiness or dizziness
• Headache
• Blurred vision
• Nausea
• Vomiting
• Diarrhea
• Constipation 
• Weight gain
• Swelling in the hands, feet or ankles
• General body aches
• Joint pain
• Back pain
• Fever 

Gabapentin is also associated with some rare adverse effects that include:[7]

• Rash
• Itching skin 
• Yellowing of skin
• Swelling in the face or throat (angioedema)
• Impaired memory or concentration
• Altered personality

Gabapentin Causes Difficulty Breathing in Special Groups

Gabapentin may cause breathing difficulties in the elderly and those with chronic obstructive pulmonary disease (COPD).[7] It can also lead to labored breathing in individuals who are using opioids alongside gabapentin. 

Gabapentin Has the Potential for Misuse and Abuse

Although not inherently addictive, gabapentin has the potential for abuse. The risk of abusing gabapentin, however, is much higher in individuals who take opioid pain relievers. This is because gabapentin enhances the psychological effects of medications in this class. Unfortunately, this action has led to a number of drug overdose deaths.[7]

Gabapentin is Linked to an Increase in Suicidal Thoughts and Behaviors 

Researchers have found that gabapentin can cause suicidal thoughts and behaviors in some individuals.[7] They are unsure why this occurs, but it appears to be more common in those with a prior history of suicidal ideations. If you or someone you know is taking gabapentin and begins to experience suicidal thoughts, consult your doctor about possibly changing your medication.

Similarly, contact a physician if you experience the following:[7]

• Unusual changes in mood
• Increased agitation
• Sudden violent outburst
• New or worsening depression

Most of these symptoms will happen during gabapentin’s half-life elimination period. They should gradually diminish as the drug nears total removal from the body. Contact your healthcare provider for further guidance if disruptive symptoms persist beyond this timeframe.

Is It Possible to Overdose If Someone Takes Too Much Gabapentin?

It is possible to overdose on gabapentin if you exceed the recommended dosage or take doses too close together. Following your prescribed dosage significantly reduces this risk. Additionally, certain medications may affect how your body absorbs and distributes gabapentin.

Combining these medications with gabapentin can lead to severe central nervous system (CNS) depression, which may cause difficulty breathing, a slowed heart rate, and confusion. In serious cases, this can result in coma or even death.

They include:[8]

• Benzodiazepines 
• Opioids 
• Acetazolamide  
• Acetophrenazine
• Agomelatine
• Alfentanil

If you are taking any of the above medications, notify your prescriber before starting gabapentin.

What Are the Signs of a Gabapentin Overdose?

Gabapentin toxicity can be life-threatening. If you experience any of the following signs of a gabapentin overdose, call poison control right away:[9][10]

• Double vision
• Diarrhea
• Drowsiness
• Fast heartbeat
• Low blood pressure
• Dizziness

If the person is not conscious or has difficulty breathing or speaking, call 911. These are signs of CNS depression and can lead to death without prompt treatment.

Note: A gabapentin overdose is more likely in individuals who are using opioid painkillers.

Treatment for Gabapentin Overdose

In cases of a mild overdose, poison control may suggest a wait-and-watch timeframe. If, during this time, symptoms improve, no treatment is necessary. However, in situations where a person has difficulty breathing or is suffering from other symptoms of CNS depression, emergency medical assistance may be necessary.

In an emergency room setting, individuals suffering from a gabapentin overdose may receive the following treatment:

• Airway management support (Ventilation and supplemental oxygen) is needed to assist with breathing.
• Gastric lavage or activated charcoal to remove gabapentin from the gastrointestinal system.
• Medications for delirium, seizure, or other complications.
• Medications such as epinephrine or norepinephrine bring extremely low blood pressure back to normal.[11]

If the person is suspected of overdosing on opioids along with gabapentin, they may be given Naloxone to reverse the effects of the opioid.[12]

How Long Does it Take Gabapentin to Completely Clear the System?

It takes two days for gabapentin to clear the body.[1] However, taking more than directed can lead to a longer overall elimination period. Additionally, individuals with renal or hepatic impairments may require more time to clear gabapentin from their system. This is also true for children under the age of three, for whom gabapentin use is not indicated.

Other factors that influence the rate at which gabapentin leaves the system include:

• Taking medications that contain gabapentin alongside a pure gabapentin prescription.
• Taking medications that interfere with gabapentin absorption.
• Taking more gabapentin than is prescribed. (this includes taking a higher dosage or taking them too close together)
• Intentionally vomiting up the medication.
• Taking activated charcoal while on gabapentin.
• Taking medications designed to clear out the stomach and digestive tract.

What Side Effects Are Abnormal to Experience During Gabapentin’s Half-Life?

Within the first five to seven hours of taking gabapentin, you may experience minor side effects. However, if you experience any side effects caused by an allergy to gabapentin, seek immediate medical attention. 

Gabapentin allergy side effects include:[12]

• Lip, mouth, throat, and tongue swelling
• Fast breathing
• Difficulty breathing
• Choking, gasping, or wheezing 
• Blueish skin and tongue
• Blueish tinge under the feet
• Blueish tinge on the palms of the hands
• Feeling confused  
• Feeling drowsy or dizzy 
• Feeling faint and having difficulty waking up
• Sudden skin rash, blisters, or peeling 

Children with an allergy to gabapentin may appear limp or floppy and have difficulty responding. Should this happen, call 911. 

Is Gabapentin a Controlled Substance?

Drugs that have a tendency to be abused or misused, as well as those lacking sufficient medical evidence for their use, are included on the U.S. Drug Enforcement Administration’s controlled substance list. Gabapentin is not on this list. Nevertheless, several states have voluntarily classified gabapentin as a controlled substance due to research indicating increased illicit use and its contribution to accidental overdose deaths.[13] 

Can Stopping Gabapentin Abruptly Cause Withdrawal Symptoms?

Short-term use of gabapentin is not linked to withdrawal. However, individuals who experience withdrawal symptoms after stopping gabapentin have usually used it for an extended period. These symptoms are primarily due to physical dependence on the medication or misuse of it.

Physical dependence occurs when your brain and body develop a tolerance to gabapentin, leading you to require higher doses for relief. Unfortunately, tolerance can develop in just a few weeks of using the medication.[14] A study published in Sage Journals found that individuals experiencing gabapentin withdrawal were taking between 600 and 8,000 mg per day, with an average dose of 3,000 mg.[15]

Symptoms of Gabapentin Withdrawal

Withdrawal symptoms from gabapentin can occur within 12 hours to seven days after discontinuation of the medication.[14] While some individuals experience mild to moderate symptoms during this period, research indicates that severe withdrawal symptoms can also occur. To mitigate these effects, some people opt for a tapering schedule, which may last up to 18 weeks.

Commonly experienced gabapentin withdrawal symptoms include:[14]

• Restlessness
• Agitation
• Anxiety
• headaches
• Nervousness
• body /stomach pain
• Nausea
• Sleeplessness
• Confusion 
• Disorientation
• Dizziness
• Excessive sweating 
• Muscle twitching 
• Light sensitivity 
• Restless limb movements
• Seizures
• High blood pressure
• Heart palpitations
• Depressed mood
• Respiratory tract infections

Researchers have drawn a significant parallel between gabapentin withdrawal and withdrawal syndromes related to alcohol and benzodiazepine cessation. This is due to gabapentin having a similar mechanism of action to these substances[16]

Does Gabapentin Withdrawal Indicate Addiction?

Withdrawal does not indicate an addiction to gabapentin; rather, it signifies a physical dependence on the medication. Addiction represents the most severe form of a substance use disorder, a relapsing disease marked by the inability to stop using an abusive substance despite facing negative consequences. 

Who is Most at Risk for Developing Gabapentin Addiction?

Gabapentin isn’t inherently addictive, but individuals with a history of substance abuse or addiction may abuse gabapentin. People who do may use it in combination with recreational drugs to enhance their high. When combined with illegal street drugs, gabapentin may lead to a more profound high and, in some cases, an overdose. Individuals who engage in polysubstance abuse may become addicted to gabapentin.

Signs of Gabapentin Addiction 

Gabapentin addiction affects how a person thinks and behaves. This results in an altered mood, losing interest in once pleasurable things, and increased risk-taking. Despite it being touted as a safe medication, gabapentin addiction may cause individuals to behave in unsafe ways. This includes doctor shopping, stealing pills from other people, and buying gabapentin illegally.

Other signs of a gabapentin addiction include:[17]

• Disrupted sleeping patterns
• Hanging out with a bad group of friends
• Missing work or school
• Having more family conflict than usual
• Experiencing withdrawal when trying to quit
• Relapsing after quitting despite negative consequences

A person using gabapentin beyond the time prescribed may appear under the influence due to its side effects. They may appear drowsy or fatigued, feel lightheaded, or complain of digestive discomfort.

DSM-5 Gabapentin Addiction Criteria

First, it is important to note that not everyone who uses gabapentin long-term becomes addicted to it. To know if someone is addicted to gabapentin, they must go through an evaluation with a mental health professional. They will use a special set of criteria published in the diagnostic manual of mental disorders to determine if the person has a substance use disorder.

If you or someone you know has experienced two or more of the following 11 symptoms in the past 12 months, you may be diagnosed with a substance use disorder or addiction:[18]

1. Using more gabapentin or higher doses of gabapentin than you need
2. Failed attempts to stop or cut down on gabapentin use
3. Spending a long time using, obtaining, or recovering from gabapentin use
4. Having cravings or an intense urge to use gabapentin
5. Falling behind in work, home, or school responsibilities due to gabapentin use
6. Continuously using gabapentin despite it causing problems in your relationships
7. Avoiding important social, work, or recreational activities due to gabapentin use
8. Continuously using gabapentin, even when it puts you in danger
9. Continuously using gabapentin despite developing or worsening a physical or mental health condition due to its use
10. Requiring a higher dose of gabapentin to feel its effects
11. Experiencing withdrawal symptoms that can only be relieved when you use gabapentin again

Treatment for Gabapentin Addiction

The treatment for any substance use disorder begins with abstaining from the addictive substance. Individuals who experience uncomfortable withdrawal symptoms from gabapentin cessation may need to resume its use and follow a taper schedule to gradually discontinue it over time. This is typically done under the careful supervision of a medical professional in a medication-assisted detox program or through close monitoring by a prescribing physician.

The next step is to uncover the root cause of gabapentin abuse through therapy. Behavioral therapies such as cognitive behavioral therapy (CBT) and dialectical behavioral therapy are effective in identifying these underlying issues and the triggers that prompt drug use. Moreover, these programs assist individuals struggling with gabapentin addiction in forming healthier thought patterns that counter unhelpful thinking, which often leads to substance use. Participants will also learn coping strategies to manage drug cravings and the specific triggers that lead them to use substances.

Locating Treatment for Gabapentin Addiction in Georgia

The treatments listed above can be provided through various programs, including inpatient, outpatient, intensive inpatient, or partial hospitalization. The appropriate level of care for someone with a gabapentin addiction depends on the severity of their addiction, which can range from mild to severe, as well as any co-occurring substance use or mental health disorders. Individuals with a dual diagnosis—having both a substance use disorder and a mental health disorder—may benefit from a program that addresses both conditions simultaneously.

For additional details about gabapentin addiction, treatment options, or general substance abuse, reach out to Southeast Detox GA. We provide a range of customized addiction treatment programs designed to assist individuals in overcoming addiction and preventing future relapses.

If you or someone you care about is having difficulty quitting gabapentin, don’t hesitate to call us today; we’re ready to help.