Gabapentin – Uses, Side Effects and Overdose

Background

Gabapentin is a structural analogue of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) that was first approved for use in the United States in 1993. It was originally developed as a novel anti-epileptic for the treatment of certain types of seizures – today it is also widely used to treat neuropathic pain. Gabapentin has some stark advantages as compared with other anti-epileptics, such as a relatively benign adverse effect profile, wide therapeutic index, and lack of appreciable metabolism making it unlikely to participate in pharmacokinetic drug interactions. It is structurally and functionally related to another GABA derivative, pregabalin.

Properties and Characteristics of Gabapentin

Drug class	Anticonvulsants
Brand Names	Gralise, Neurontin
Synonyms	Gabapentin, Gabapentina, Gabapentine, Gabapentino, Gabapentinum
Molecular Formula	C9H17NO2
Molecular Weight	171.24 g/mol
IUPAC Name	2-[1-(aminomethyl)cyclohexyl]acetic acid
Structural formula of main components
Pure active ingredient	Gabapentin
Appearance	White to off-white crystalline solid
Melting point	165 – 167 °C
Solubility	In water, 4.49X10+3 mg/L at 25 °C
Excretion	Gabapentin is eliminated solely in the urine as unchanged drug
Storage	Store Neurontin Tablets and Capsules at 25 °C (77 °F)
Available Forms	Tablets and Capsules
Prescription	Doctor’s prescription is required

What are the uses of Gabapentin

Epilepsy

Gabapentin is used in the treatment of epilepsy which is a brain disorder characterized by uncontrolled jerking movements and loss of consciousness.

Postherpetic Neuralgia

Gabapentin is used in the treatment complication of shingles, which is caused by the chickenpox virus characterized by pain or burning sensation of the skin.

Information given here is based on the salt content of the medicine. Uses and effects of the medicine may vary from person to person. It is advisable to consult a Neurologist before using this medicine.

What side effects can this medication cause?

Gabapentin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Drowsiness
• Tiredness or weakness
• Dizziness
• Headache
• Uncontrollable shaking of a part of your body
• Double or blurred vision
• Unsteadiness
• Anxiety
• Memory problems
• Strange or unusual thoughts
• Unwanted eye movements
• Nausea
• Vomiting
• Heartburn
• Diarrhea
• Dry mouth
• Constipation
• Increased appetite
• Weight gain
• Swelling of the hands, feet, ankles, or lower legs
• Back or joint pain
• Fever
• Runny nose, sneezing, cough, sore throat, or flu-like symptoms
• Ear pain
• Red, itchy eyes (sometimes with swelling or discharge)

Some side effects may be serious. If you experience any of the following symptoms, call your doctor immediately:

• Rash
• Itching
• Swelling of the face, throat, tongue, lips, or eyes
• Soarseness
• Difficulty swallowing or breathing
• Seizures
• Difficulty breathing; bluish-tinged skin, lips, or fingernails; confusion; or extreme sleepiness

Gabapentin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

Mechanism of action

The precise mechanism through which gabapentin exerts its therapeutic effects is unclear. The primary mode of action appears to be at the auxillary α2δ-1 subunit of voltage-gated calcium channels (though a low affinity for the α2δ-2 subunit has also been reported). The major function of these subunits is to facilitate the movement of pore-forming α1 subunits of calcium channels from the endoplasmic reticulum to the cell membrane of pre-synaptic neurons. There is evidence that chronic pain states can cause an increase in the expression of α2δ subunits and that these changes correlate with hyperalgesia.8 Gabapentin appears to inhibit the action of α2δ-1 subunits, thus decreasing the density of pre-synaptic voltage-gated calcium channels and subsequent release of excitatory neurotransmitters. It is likely that this inhibition is also responsible for the anti-epileptic action of gabapentin.

There is some evidence that gabapentin also acts on adenosine receptors and voltage-gated potassium channels,13 though the clinical relevance of its action at these sites is unclear.

Gabapentin may interact with other medications

Gabapentin oral capsule can interact with several other medications. Different interactions can cause different effects. For instance, some can interfere with how well a drug works, while others can cause increased side effects.

Below is a list of medications that can interact with gabapentin. This list does not contain all drugs that may interact with gabapentin.

Before taking gabapentin, be sure to tell your doctor and pharmacist about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Opioids

When used with gabapentin, opioids can cause dangerous effects in the body. Some examples of these drugs include morphine, hydrocodone, and oxycodone.

Taking gabapentin with an opioid increases your risk for severe sleepiness, respiratory depression, coma, and even death.

Stomach acid drugs

When used with gabapentin, certain drugs used to treat stomach acid problems can reduce the amount of gabapentin in your body. This can make it less effective. Taking gabapentin 2 hours after taking these drugs can help prevent this problem. Examples of these drugs include:

• Aluminum hydroxide
• Magnesium hydroxide

Dosing

The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage forms (capsules, liquid, and tablets):

For epilepsy:

Adults and children 12 years of age and older—At first, 300 milligrams (mg) 3 times per day. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 1800 mg per day (600 mg 3 times per day).

Children 3 to 11 years of age—Dose is based on body weight and must be determined by your doctor. The starting dose is 10 to 15 milligrams (mg) per kilogram (kg) of body weight per day and divided in 3 doses. Your doctor may adjust your dose as needed and tolerated.

Children younger than 3 years of age—Use and dose must be determined by your doctor.

For postherpetic neuralgia:

Adults— At first, 300 milligrams (mg) as a single dose in the evening. Your doctor may adjust your dose as needed and tolerated. However, the dose is usually not more than 1800 mg per day.

Children—Use and dose must be determined by your doctor.

Risk of Gabapentin overdose

Despite research in this area, it is not always clear whether suicidal behaviors in people who take gabapentin are a result of the drug itself or related to an existing mental health condition.

It is clear, however, that the risk of overdose from the drug is higherTrusted Source if a person also has a mental health condition such as depression.

In addition, when taking gabapentin, a person should monitor themselves carefully to make sure that they are not accidentally taking the wrong dosage.

People should also check on loved ones and minors taking this medication and seek help if there is any concern that they may have suicidal thoughts or behaviors.

According to the FDA, there have been reports of oral overdoses from taking up to 49 grams of the drug.

Symptoms of an overdose may include:

• Sleepiness
• Lethargy
• Double vision
• Slurred speech
• Diarrhea
• Coma, in cases when someone has chronic renal failure and has received treatment with Neurontin

What precautions should I take while on gabapentin (Neurontin)?

• Keep all your health care appointments. Your doctor may order tests to keep an eye on your health while you’re on gabapentin.
• Gabapentin is available in different formulations for different uses. Make sure you are not taking more than one product containing gabapentin. Also, ensure that your pharmacy gives you the form of the medication you have been prescribed and not a substitute.
• If you take antacids such as Mylanta or Maalox, be sure to take them at least 2 hours before taking your gabapentin capsules, tablets, or oral solution.
• If you are having a dental procedure or surgery, tell your doctors you are taking gabapentin.
• This medication can make you drowsy and/or dizzy. Do not drive, operate heavy machinery, or do anything that requires focus until you know how gabapentin affects you.
• Gabapentin can cause suicidal thinking and behaviors. Monitor yourself or your child for any changes in mental health during treatment. Symptoms can include agitation, irritability, anxiety, depression, withdrawal from friends and family, and talking about harming themselves.

Warnings for other groups

For pregnant women: The use of gabapentin has not been studied in humans during pregnancy. Research in animals has shown negative effects to the fetus when the mother takes the drug. However, animal studies don’t always predict the way humans would respond.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used if the potential benefit justifies the potential risk to the fetus. Call your doctor if you become pregnant while taking this drug.

If your doctor prescribes gabapentin for you while you’re pregnant, ask about the NAAED Pregnancy Registry. This registry tracks the effects of anti-seizure drugs on pregnancy. Information can be found at aedpregnancyregistry.org.

For women who are breastfeeding: Gabapentin may pass into breast milk and cause serious side effects in a breastfeeding child. Tell your doctor if you are breastfeeding. You should decide together if you should stop taking this drug or stop breastfeeding.

For seniors: Kidney function may decrease with age. You may process this drug more slowly than younger people. Your doctor may start you on a lowered dose so that too much of this drug does not build up in your body. Too much of the drug in your body can be dangerous.

For children: Gabapentin has not been studied in children for the management of postherpetic neuralgia. It should not be used in people younger than 18 years. This drug should not be used to treat partial seizures in children younger than 3 years.