Home Drug Guide Gabapentin

Drug Guide

Generic Name

Gabapentin

Brand Names Neurontin, Gralise

Classification

Therapeutic: Anticonvulsant, Neuropathic Pain Agent

Pharmacological: Gamma-Aminobutyric Acid (GABA) Analog

FDA Approved Indications

Epilepsy (adjunctive therapy)
Postherpetic neuralgia

Mechanism of Action

Gabapentin is thought to affect the way that nerves transmit signals related to pain and seizures, although its precise mechanism is not fully understood. It binds to the alpha-2-delta subunit of voltage-gated calcium channels in the nervous system, inhibiting excitatory neurotransmitter release.

Dosage and Administration

Adult: Typically 300 mg on Day 1, titrated up based on response and tolerability to a maximum of 3600 mg per day divided into multiple doses.

Pediatric: Dosing based on weight and clinical response; specific dosing guidelines are provided in prescribing information.

Geriatric: Start at lower dose due to increased risk of adverse effects; renal function should be assessed prior to dosing.

Renal Impairment: Dose adjustment is necessary; dosing based on creatinine clearance.

Hepatic Impairment: No specific adjustment required, but caution is advised.

Pharmacokinetics

Absorption: Absorbed orally with a bioavailability of approximately 60%.

Distribution: Widespread distribution, minimal protein binding.

Metabolism: Practically none; unchanged in urine.

Excretion: Excreted unchanged via the kidneys.

Half Life: Approximately 5 to 7 hours in individuals with normal renal function.

Contraindications

Hypersensitivity to gabapentin or the formulation used.

Precautions

Renal impairment: Dose adjustment required.
Suicidal thoughts or behaviors: Monitor patients closely.
Caution in elderly due to increased sensitivity to side effects.

Adverse Reactions - Common

Dizziness (Common)
Somnolence (Common)
ataxia (Common)
Peripheral edema (Less common)

Adverse Reactions - Serious

Angioedema (Rare)
Suicidal thoughts or behavior (Less common)
Center nervous system depression (Rare)

Drug-Drug Interactions

The use with opioids may enhance CNS depression.
Antacids may decrease bioavailability when taken simultaneously.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for effectiveness, adverse effects, renal function, mental status, and signs of depression or suicidal ideation.

Diagnoses:

Risk for injury related to dizziness or somnolence.
Risk for suicidal ideation.

Implementation: Administer as prescribed, monitor for adverse effects, and educate patients about potential CNS effects.

Evaluation: Assess for seizure control, pain relief, and side effects.

Patient/Family Teaching

Take medication exactly as prescribed.
Do not suddenly discontinue without consulting healthcare provider.
Be cautious when performing activities requiring alertness.
Report any suicidal thoughts, swelling, or allergic reactions.

Special Considerations

Black Box Warnings:

Suicidal thoughts and behavior.
Psychiatric and behavioral reactions.

Genetic Factors: None known.

Lab Test Interference: None significant.

Overdose Management

Signs/Symptoms: Dizziness, double vision, slurred speech, drowsiness, lethargy, diarrhea, mild tachycardia,/bradycardia.

Treatment: Supportive care, ensure airway patency, gastric decontamination if early, hemodialysis may be considered in severe cases.

Storage and Handling

Storage: Store at room temperature between 20-25°C (68-77°F).

Stability: Stable for up to 24 months as per manufacturer.