Gabapentin


Generic Medicine Info
Indications and Dosage
Oral
Epilepsy
Adult: As monotherapy or adjunctive therapy for the treatment of partial seizures with or without secondary generalisation: As conventional tab/cap/oral solution: Initial titration schedule: Day 1: 300 mg once daily. Day 2: 300 mg bid. Day 3: 300 mg tid. Alternatively, 300 mg tid on day 1, then increase further in increments of 300 mg daily every 2-3 days according to individual response and tolerability. Effective dosing range: 900-3,600 mg daily. Total daily doses are given in 3 equally divided doses. Max dosage interval: 12 hours.
Child: As adjunctive therapy: As conventional tab/cap/oral solution: 3-11 years Initially, 10-15 mg/kg daily, titrate over a period of approx 3 days until the effective dose is achieved. Usual maintenance dose: 3-4 years 40 mg/kg daily; 5-11 years 25-35 mg/kg daily. Max: 50 mg/kg daily. Total daily doses are given in 3 equally divided doses. Max dosage interval: 12 hours. ≥12 years Same as adult dose. Treatment and dosage recommendations may vary among countries and individual products (refer to detailed product guidelines).

Oral
Neuropathic pain
Adult: For the treatment of cases such as painful diabetic neuropathy, postherpetic neuralgia, and trigeminal neuralgia: As conventional tab/cap/oral solution: Initial titration schedule: Day 1: 300 mg once daily. Day 2: 300 mg bid. Day 3: 300 mg tid. Alternatively, initiate at 900 mg daily in 3 equally divided doses, then increase further in increments of 300 mg daily every 2-3 days according to individual response and tolerability. Max: 3,600 mg daily.

Oral
Postherpetic neuralgia
Adult: As gastroretentive tab: Initial titration schedule: Day 1: 300 mg once daily. Day 2: 600 mg once daily. Day 3-6: 900 mg once daily. Day 7-10: 1,200 mg once daily. Day 11-14: 1,500 mg once daily. Day 15: 1,800 mg once daily.
Renal Impairment
Epilepsy; Neuropathic pain:
As conventional tab/cap/oral solution: Anuric patients undergoing haemodialysis who are naive to gabapentin: Loading dose: 300-400 mg followed by 200-300 mg after each haemodialysis session; no doses are given on dialysis-free days. Patients undergoing haemodialysis: Maintenance dose is based on CrCl; additional dose of 200-300 mg after each haemodialysis session is recommended.
CrCl (mL/min) Dosage
<15 300 mg every other day to 300 mg daily in 3 divided doses.
15-29 300 mg every other day to 600 mg daily in 3 divided doses.
30-49 300-900 mg daily in 3 divided doses.
50-79 600-1,800 mg daily in 3 divided doses.

Postherpetic neuralgia:
As gastroretentive tab: Patients receiving haemodialysis: Not recommended.
CrCl (mL/min) Dosage
<30 Not recommended.
30-60 Initially, 300 mg once daily, followed by 600-1,800 mg once daily according to individual response and tolerability.
Administration
May be taken with or without food. FC tab/tab: May be divided along the score line.
gastroretentive tab: Should be taken with food. Take with evening meal. Swallow whole, do not split/crush/chew.
Special Precautions
Patient with mixed seizures (including absences), compromised respiratory function, respiratory disease, neurological disease, history of substance abuse, myasthenia gravis, poor general health (e.g. low body weight, organ transplant recipient). Avoid abrupt withdrawal; reduce dose gradually over at least 7 days (regardless of indication). Patient concomitantly receiving CNS depressants (e.g. opioids). Various preparations are available that are not interchangeable; refer to specific product guideline for detailed information. Renal impairment. Children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Anaphylaxis, angioedema, suicidal ideation and behaviour, acute pancreatitis, onset of new types of seizures, increase in seizure frequency; dizziness, somnolence, confusion, mental impairment; drug abuse and dependence, withdrawal symptoms; neuropsychiatric reactions (e.g. emotional lability, thought disorder, hostility, hyperkinesia) in children.
Blood and lymphatic system disorders: Leucopenia.
Ear and labyrinth disorders: Otitis media, vertigo.
Eye disorders: Visual disturbances (e.g. amblyopia, diplopia).
Gastrointestinal disorders: Nausea, vomiting, diarrhoea, abdominal pain, dry mouth or throat, flatulence, dyspepsia, constipation, dental abnormalities, gingivitis.
General disorders and administration site conditions: Fever, fatigue, asthenia, pain, peripheral oedema, abnormal gait, flu syndrome, fractures.
Infections and infestations: Viral infection.
Injury, poisoning and procedural complications: Accidental injury.
Investigations: Decreased WBC, weight gain.
Metabolism and nutrition disorders: Anorexia, increased appetite.
Musculoskeletal and connective tissue disorders: Arthralgia, myalgia, twitching, back pain.
Nervous system disorders: Headache, ataxia, amnesia, dysarthria, abnormal sensation (e.g. paraesthesia), tremor, abnormal coordination, nystagmus, abnormal reflexes (e.g. increased, decreased, or absent), abnormal thinking.
Psychiatric disorders: Anxiety, depression, insomnia, nervousness.
Renal and urinary disorders: UTI.
Reproductive system and breast disorders: Impotence.
Respiratory, thoracic and mediastinal disorders: Pneumonia, respiratory tract infection, dyspnoea, bronchitis, pharyngitis, cough, rhinitis.
Skin and subcutaneous tissue disorders: Rash, pruritus, acne, purpura, abrasion.
Vascular disorders: Hypertension, vasodilatation.
Potentially Fatal: Drug reaction with eosinophilia and systemic symptoms (DRESS)/multiorgan hypersensitivity; severe respiratory depression.
Patient Counseling Information
This drug may cause dizziness and drowsiness, if affected, do not drive or operate machinery.
Monitoring Parameters
Assess for history of substance abuse prior to initiation of treatment. Monitor renal function periodically. Monitor for symptoms of respiratory depression and sedation in patients with respiratory disease. Observe for signs and symptoms of suicidal ideation and behaviour, drug abuse and dependence (e.g. drug-seeking behaviour, development of tolerance), mental alertness, hypersensitivity.
Overdosage
Symptoms: Dizziness, drowsiness, lethargy, double vision, slurred speech, mild diarrhoea, loss of consciousness; coma (particularly when used with other CNS depressants). Management: Supportive treatment. Consider haemodialysis in patients with severe renal impairment.
Drug Interactions
Reduced bioavailability with antacids containing Al and Mg.
Potentially Fatal: Concomitant use with CNS depressants (e.g. opioids, benzodiazepines, antidepressants, antihistamines) may cause respiratory and CNS depression.
Food Interaction
May increase the risk of CNS depression with alcohol. Increased rate and extent of absorption when given with food, particularly high-fat meals (extended-release tab).
Lab Interference
May cause false-positive readings in the semi-quantitative determination of total urine protein by dipstick tests.
Action
Description: Gabapentin is structurally related to the neurotransmitter GABA. However, it does not bind to GABAA or GABAB receptors nor influence the synthesis or uptake of GABA. The exact mechanisms are unknown but it has been shown that gabapentin binds with high affinity to the α-2-δ-1 subunit of voltage-gated Ca channels, which may be found presynaptically, and may facilitate the release of excitatory neurotransmitters that participate in epileptogenesis and nociception.
Pharmacokinetics:
Absorption: Absorbed from the gastrointestinal tract. Increased rate and extent of absorption with food (gastroretentive tab). Bioavailability: Dose-dependent (inversely proportional to the dose). Time to peak plasma concentrations: 2-4 hours (conventional formulation); 8 hours (gastroretentive tab).
Distribution: Widely distributed in the body. Crosses the placenta and enters breast milk. Volume of distribution: 57.7 L. Plasma protein binding: <3%.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: Not metabolised.
Excretion: Via urine (as unchanged drug). 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/cap/gastroretentive tab: Store between 15-30°C. Oral solution: Store between 2-8°C. Storage recommendations may vary among countries and individual products. Refer to detailed product guideline.
MIMS Class
Anticonvulsants / Drugs for Neuropathic Pain
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 25/03/2022.

Anon. Gabapentin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 08/03/2022.

Buckingham R (ed). Gabapentin. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/03/2022.

Gabapentin 800 mg Tablets (Sandoz Limited). MHRA. https://products.mhra.gov.uk. Accessed 08/03/2022.

Gabapentin Glenmark 50 mg/mL Oral Solution (Glenmark Pharmaceuticals Europe Limited). MHRA. https://products.mhra.gov.uk. Accessed 08/03/2022.

Gralise Tablet, Film Coated (Almatic Pharma LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/03/2022.

Joint Formulary Committee. Gabapentin. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/03/2022.

Neurontin 100 mg Hard Capsules (Upjohn UK Limited). MHRA. https://products.mhra.gov.uk. Accessed 08/03/2022.

Neurontin Capsule; Tablet (Viatris Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 08/03/2022.

Neurontin Capsule; Tablet, Film Coated; Solution (Parke-Davis Div of Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/03/2022.

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 © 2022 MIMS. All rights reserved. Powered by MIMS.com
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