Gabapentin Pharmacology

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 is structurally related to GABA. However, it does not bind to GABAA or GABAB receptors, and it does not appear to influence synthesis or uptake of GABA.

High affinity gabapentin binding sites have been located throughout the brain; these sites correspond to the presence of voltage-gated calcium channels specifically possessing the alpha-2-delta-1 subunit.

Gabapentin 800 mg Tab-IVA
Gabapentin 800 mg Tab-IVA

This channel appears to be located presynaptically, and may modulate the release of excitatory neurotransmitters which participate in epileptogenesis and nociception.

Absorption

Variable, from proximal small bowel by L-amino transport system; saturable process; dose-dependent

Vd: 58 ± 6 L; CSF concentrations are ~20% of plasma concentrations

Metabolism

Not metabolized

Excretion

Proportional to renal function; urine (as unchanged drug)

Clearance: Apparent oral clearance is directly proportional to CrCl: Clearance in infants is highly variable; oral clearance (per kg) in children <5 years of age is higher than in children ≥5 years of age

Time to Peak

Immediate release: Infants 1 month to Children 12 years: 2 to 3 hours; Adults: 2 to 4 hours; Extended release: 8 hours

Half-Life Elimination

Infants 1 month to Children 12 years: 4.7 hours

Adults, normal: 5 to 7 hours; increased half-life with decreased renal function; anuric adult patients: 132 hours; adults during hemodialysis: 3.8 hours

Protein Binding

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