Gabapentin Chemical and Physical Properties

Gabapentin was introduced in 1993 in the UK and early 1994 in the USA as an adjunctive therapy in the treatment of refractory partial seizures and secondarily generalized tonic-clonic seizures. Although being a lipophilic analog of the neurotransmitter GABA, gabapentin appears to exert its anticonvulsive function by a GABA receptor independent mechanism, possibly involving the L-system amino acid transporter protein.

Gabapentin easily crosses the blood brain barrier and exhibits a favorable pharmacokinetic profile with high tolerability. It does not interfere with the metabolism of other concomitant administered antiepileptic drugs, thus having a low potential for drug interactions. Studies are currently underway for the use of gabapentin as mono-therapy for the treatment of various seizures.

Gabapentin capsules, tablets, and oral solution are used along with other medications to help control certain types of seizures in people who have epilepsy. Gabapentin capsules, tablets, and oral solution are also used to relieve the pain of postherpetic neuralgia (PHN; the burning, stabbing pain or aches that may last for months or years after an attack of shingles). Gabapentin extended-release tablets (Horizant) are used to treat restless legs syndrome (RLS; a condition that causes discomfort in the legs and a strong urge to move the legs, especially at night and when sitting or lying down). Gabapentin is in a class of medications called anticonvulsants. Gabapentin treats seizures by decreasing abnormal excitement in the brain. Gabapentin relieves the pain of PHN by changing the way the body senses pain. It is not known exactly how gabapentin works to treat restless legs syndrome.

Gabapentin (Generic Neurontin ) is used to help control partial seizures (convulsions) in the treatment of epilepsy. This medicine cannot cure epilepsy and will only work to control seizures for as long as you continue to take it.

Gabapentin (Generic Neurontin ) is also used to manage a condition called postherpetic neuralgia, which is pain that occurs after shingles. It’s also taken for nerve pain. Nerve pain can be caused by different illnesses, including diabetes and shingles, or it can happen after an injury.

Gabapentin (Generic Neurontin ) works in the brain to prevent seizures and relieve pain for certain conditions in the nervous system. It is not used for routine pain caused by minor injuries or arthritis. Gabapentin is an anticonvulsant.

Occasionally, gabapentin (Generic Neurontin ) is used to prevent migraine headaches. Gabapentin (Neurontin) and pregabalin (Lyrica) are anticonvulsants and nerve pain medicines which have structural similarities to the inhibitory neurotransmitter GABA.

Gabapentin (Generic Neurontin ) is available only with your doctor’s prescription.

Gabapentin (Generic Neurontin ) is available in the following dosage forms:
Capsule
Tablet
Tablet, Extended Release, 24 HR
Solution
Suspension

DOSAGE FORMS AND STRENGTHS of Gabapentin
Capsules
100 mg: white hard gelatin capsules printed with “PD” on the body and300 mg: yellow hard gelatin capsules printed with “PD” on the body and “Neurontin/300 mg” on the cap
400 mg: orange hard gelatin capsules printed with “PD” on the body and “Neurontin/400 mg” on the cap
Tablets
600 mg: white elliptical film-coated scored tablets debossed with “NT” and “16” on one side
Gabapentin 800 mg: white elliptical film-coated scored tablets debossed with “NT” and “26” on one side
Oral solution: 250 mg per 5 mL (50 mg per mL), clear colorless to slightly yellow solution

Gabapentin (Generic Neurontin ) was developed in 1993 and has indications for shingles (‘postherpetic neuralgia’) and partial-onset seizures. It has had a growing popularity in off-label uses for fibromyalgia, pain from a variety of causes, migraine, cocaine withdrawal, anxiety, and insomnia. A related compound, gabapentin encarbil (Horizant), is approved for shingles and restless leg syndrome. Pregabalin was developed in 2004 and is approved for nerve pain from diabetes and spinal cord injuries, fibromyalgia, and adjunctive treatment of partial-onset seizures. Although prescribed off-label for anxiety in the U.S., it is approved for this purpose in the U.K., where it is sometimes called the ‘new Valium’.

Gabapentin comes as a capsule, a tablet, an extended-release (long-acting) tablet, and an oral solution (liquid) to take by mouth. Gabapentin capsules, tablets, and oral solution are usually taken with a full glass of water (8 ounces [240 milliliters]), with or without food, three times a day.

These medications should be taken at evenly spaced times throughout the day and night; no more than 12 hours should pass between doses. The extended-release tablet (Horizant) is taken with food once daily at about 5 PM. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take gabapentin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Gabapentin extended-release tablets cannot be substituted for another type of gabapentin product. Be sure that you receive only the type of gabapentin that was prescribed by your doctor. Ask your pharmacist if you have any questions about the type of gabapentin you were given.

Swallow the extended-release tablets whole; do not cut, chew, or crush them.

If your doctor tells you to take one-half of a regular tablet as part of your dose, carefully split the tablet along the score mark. Use the other half-tablet as part of your next dose. Properly dispose of any half-tablets that you have not used within several days of breaking them.

If you are taking gabapentin to control seizures or PHN, your doctor will probably start you on a low dose of gabapentin and gradually increase your dose as needed to treat your condition. If you are taking gabapentin to treat PHN, tell your doctor if your symptoms do not improve during your treatment.

Gabapentin may help to control your condition but will not cure it. Continue to take gabapentin even if you feel well. Do not stop taking gabapentin without talking to your doctor, even if you experience side effects such as unusual changes in behavior or mood. If you suddenly stop taking gabapentin tablets, capsules, or oral solution, you may experience withdrawal symptoms such as anxiety, difficulty falling asleep or staying asleep, nausea, pain, and sweating. If you are taking gabapentin to treat seizures and you suddenly stop taking the medication, you may experience seizures more often. Your doctor may decrease your dose gradually over at least a week.

Your doctor or pharmacist will give you the manufacturer’s patient information sheet (Medication Guide) when you begin treatment with gabapentin and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visit the Food and Drug Administration (FDA) website (http://www.fda.gov/Drugs) or the manufacturer’s website to obtain the Medication Guide.

Computed Properties

Molecular Weight 171.23678 g/mol
Molecular Formula C9H17NO2
XLogP3 -1.1
Hydrogen Bond Donor Count 2
Hydrogen Bond Acceptor Count 3
Rotatable Bond Count 3
Exact Mass 171.125929 g/mol
Monoisotopic Mass 171.125929 g/mol
Topological Polar Surface Area 63.3 A^2
Heavy Atom Count 12
Formal Charge 0
Complexity 162
Isotope Atom Count 0
Defined Atom Stereocenter Count 0
Undefined Atom Stereocenter Count 0
Defined Bond Stereocenter Count 0
Undefined Bond Stereocenter Count 0
Covalently-Bonded Unit Count 1

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
  • hoarseness
  • 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.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

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