Gabapentin


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO Epilepsy Initial: 300 mg once daily on the 1st day, 300 mg bid on the 2nd day, and 300 mg tid on the 3rd day. Alternatively, 300 mg tid on the 1st day. Doses may be further increased in 300 mg/day increments every 2-3 days according to individual response and tolerability. Effective dosing range: 900-3,600 mg daily. Total daily dose must be given in 3 equally divided doses, at max dose interval not exceeding 12 hours. Neuropathic pain Initial: 300 mg once daily on the 1st day, 300 mg bid on the 2nd day and 300 mg tid on the 3rd day. Alternatively, 900 mg daily in 3 equally divided doses as starting dose. Doses may be further increased in 300 mg/day increments every 2-3 days according to individual response and tolerability. Max: 3,600 mg/day. Restless leg syndrome As gabapentin enacarbil: Modified-release preparation: Moderate to severe: 600 mg once daily at approx 5 pm. Postherpetic neuralgia As gabapentin enacarbil: Modified-release preparation: Initial: 600 mg once daily in the morning for 3 days, then increased to 600 mg bid.
Dosage Details
Oral
Epilepsy
Adult: Initially, 300 mg once daily on the 1st day, 300 mg bid on the 2nd day, and 300 mg tid on the 3rd day. Alternatively, 300 mg tid on the 1st day. Thereafter, doses may be further increased in 300 mg daily increments every 2-3 days according to individual response and tolerability. Effective dosing range: 900-3,600 mg daily. Total daily dose must be given in 3 equally divided doses, at max dose interval not exceeding 12 hours.
Child: ≥6 years Initially, 10-15 mg/kg daily, may be titrated over a period of approx 3 days until effective dose is achieved. Effective dosing range: 25-35 mg/kg daily. Max: 50 mg/kg daily. Total daily dose must be given in 3 equally divided doses at max dose interval not exceeding 12 hours.

Oral
Neuropathic pain
Adult: Initially, 300 mg once daily on the 1st day, 300 mg bid on the 2nd day, and 300 mg tid on the 3rd day. Alternatively, 900 mg daily in 3 equally divided doses as starting dose. Thereafter, doses may be further increased in 300 mg daily increments every 2-3 days according to individual response and tolerability. Max: 3,600 mg daily.

Oral
Postherpetic neuralgia
Adult: As gabapentin enacarbil: Modified-release preparation: Initially, 600 mg once daily in the morning for 3 days, then increased to 600 mg bid.

Oral
Restless leg syndrome
Adult: As gabapentin enacarbil: Modified-release preparation: Moderate to severe: 600 mg once daily at approx 5 pm.
Renal Impairment
Epilepsy, Neuropathic pain: All doses are given in 3 divided doses. In anuric patient undergoing haemodialysis who never received gabapentin: Loading dose: 300-400 mg, followed by 200-300 mg after each 4-hour haemodialysis. In renally impaired patient undergoing haemodialysis: additional 200-300 mg in the maintenance dose after each 4-hour haemodialysis.
CrCl (mL/min) Dosage
<15 300 mg on alternate days to 300 mg daily.
15-29 300 mg on alternate days to 600 mg daily.
30-49 300-900 mg daily.
50-79 600-1,800 mg daily.
Restless leg syndrome: As gabapentin enacarbil: Modified-release preparation: Haemodialysis: Not recommended.
CrCl (mL/min) Dosage
<15 300 mg on alternate days.
15-29 300 mg daily.
30-59 Initially, 300 mg daily, increased to 600 mg daily, if necessary.
Postherpetic neuralgia: As gabapentin enacarbil: Modified-release preparation: Haemodialysis: Maintenance: 300 mg after each dialysis, may increase to 600 mg if necessary. All doses are based on individual response and tolerability.
CrCl (mL/min) Dosage
<15 Maintenance: 300 mg in the morning on alternate days, may increase to 300 mg once daily in the morning if needed.
15-29 Titration: 300 mg in the morning on day 1 and 3; Maintenance: 300 mg daily in the morning, may increase to 300 mg bid if needed; Tapering: If taking 300 mg bid, may reduce dose to 300 mg once daily in the morning for 1 week; If taking 300 mg once daily, no tapering needed.
30-59 Titration: 300 mg in the morning for 3 days; Maintenance: 300 mg bid, may increase to 600 mg bid as needed; Tapering: May reduce current dose to once daily in the morning for 1 week.
Administration
May be taken with or without food.
Special Precautions
Patients with mixed seizures including absences, compromised respiratory function, respiratory or neurological disease, history of substance abuse (e.g. alcohol, benzodiazepines, cannabis, cocaine, opioids). Concomitant use with opioids. Avoid abrupt withdrawal. Renal impairment. Children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Suicidal ideation and behaviour, neuropsychiatric effects in children (e.g. emotional lability, hostility, changes in behaviour and thinking, hyperkinesia), acute pancreatitis, respiratory depression, anaphylaxis, angioedema.
Blood and lymphatic system disorders: Leucopenia, thrombocytopenia.
Ear and labyrinth disorders: Vertigo, tinnitus.
Eye disorders: Nystagmus, amblyopia, diplopia.
Gastrointestinal disorders: Nausea, vomiting, diarrhoea, dry mouth, dental abnormality, dyspepsia, gingivitis, flatulence, constipation.
General disorders and admin site conditions: Fatigue, fever, peripheral oedema, abnormal gait, asthenia, malaise.
Infections and infestations: Viral infection, pneumonia, otitis media.
Injury, poisoning and procedural complications: Accidental injury, fracture.
Investigations: Weight gain, decreased WBC.
Metabolism and nutrition disorders: Anorexia, increased appetite.
Musculoskeletal and connective tissue disorders: Back pain, arthralgia, myalgia.
Nervous system disorders: Somnolence, dizziness, headache, ataxia, amnesia, tremor.
Psychiatric disorders: Confusion, depression, nervousness, anxiety.
Reproductive system and breast disorders: Impotence.
Respiratory, thoracic and mediastinal disorders: Dyspnoea, bronchitis, cough, rhinitis.
Skin and subcutaneous tissue disorders: Rash, pruritus, acne.
Vascular disorders: Hypertension, vasodilatation.
Potentially Fatal: Multiorgan hypersensitivity such as drug reaction with eosinophilia and systemic symptoms (DRESS).
Patient Counseling Information
This drug may cause dizziness and drowsiness, if affected, do not drive or operate machinery.
MonitoringParameters
Monitor renal function at baseline and periodically thereafter. Assess for signs of multiorgan hypersensitivity and suicidality (e.g. suicidal thoughts, depression, behavioural changes).
Overdosage
Symptoms: Dizziness, drowsiness, double vision, slurred speech, mild diarrhoea, lethargy, and loss of consciousness. Management: Symptomatic and supportive treatment. May consider haemodialysis in patients with severe renal impairment.
Drug Interactions
Increased risk of CNS depression (e.g. somnolence, sedation and respiratory depression) with opioids (e.g. morphine). May reduce bioavailability with antacids. May reduce renal clearance with cimetidine.
Food Interaction
May enhance CNS depressant effect of alcohol.
Lab Interference
May lead to false-positive result with certain dipstick test for total urine protein.
Action
Description: Gabapentin is structurally related to neurotransmitter GABA. It does not bind to GABAA or GABAB receptors nor influence the synthesis or uptake of GABA. It binds with high affinity to the α-2-δ-1 subunit of voltage-gated Ca channels, thereby modulating the release of excitatory neurotransmitters which participate in epileptogenesis and nociception.
Pharmacokinetics:
Absorption: Variably absorbed from the gastrointestinal tract. Bioavailability: Approx 60% (gabapentin). As gabapentin enacarbil: Approx 75% (with food); 42-65% (fasting). Time to peak plasma concentration: Approx 2-4 hours (gabapentin); As gabapentin enacarbil: 5 hours (fasting); 7.3 hours (with food).
Distribution: Widely distributed in the body. Crosses placenta and enters breast milk. Volume of distribution: 58±6 L (gabapentin); 76 L (gabapentin enacarbil). Plasma protein binding: <3%.
Metabolism: As gabapentin enacarbil: Undergoes extensive first-pass metabolism mainly in enterocytes and to a lesser extent in the liver to form gabapentin, CO2, acetaldehyde and isobutyric acid.
Excretion: As gabapentin: Mainly via urine (as unchanged drug). As gabapentin enacarbil: Mainly via urine (94%); faeces (5%). Elimination half-life: Approx 5-7 hours.
Chemical Structure

Chemical Structure Image
Gabapentin

Source: National Center for Biotechnology Information. PubChem Database. Gabapentin, CID=3446, https://pubchem.ncbi.nlm.nih.gov/compound/Gabapentin (accessed on Jan. 22, 2020)

Storage
Conventional tab and cap: Store below 25°C. Oral solution: Store between 2-8°C. Extended-release tab: Store at 25°C. Protect from moisture.
ATC Classification
N03AX12 - gabapentin ; Belongs to the class of other antiepileptics.
References
Anon. Gabapentin. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 07/06/2019.

Anon. Gabapentin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 07/06/2019.

Buckingham R (ed). Gabapentin. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 07/06/2019.

Gabapentin Rosemont 50 mg/mL Oral Solution (Rosemont Pharmaceuticals Ltd). MHRA. https://products.mhra.gov.uk/. Accessed 07/06/2019.

Gralise (Gabapentin) Tablets. U.S. FDA. https://www.fda.gov/. Accessed 23/07/2014.

Gralise Tablet, Film Coated (Depomed, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 07/06/2019.

Horizant (Gabapentin Enacarbil) Extended-Release Tablets. U.S. FDA. https://www.fda.gov/. Accessed 07/06/2019.

Horizant Extended-Release Tablets (Patheon Inc.). U.S. FDA. https://www.fda.gov/. Accessed 07/06/2019.

Horizant Tablet, Extended Release (Arbor Pharmaceuticals). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 07/06/2019.

Horizant Tablet, Extended Release (GlaxoSmithKline LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 23/07/2014.

Disclaimer: This information is independently developed by MIMS based on Gabapentin from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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