1. Introduction
Gabapentin is a gamma-aminobutyric acid (GABA) analogue used to treat neuropathic pain, epilepsy, and other off-label conditions. Although it is structurally similar to GABA, it does not act directly on GABA receptors. Instead, it binds to voltage-gated calcium channels in the central nervous system, reducing nerve excitability and pain transmission.
2. Indications
- Approved Indications:
- Neuropathic pain (e.g., diabetic neuropathy, postherpetic neuralgia).
- Epilepsy (adjunctive therapy for partial seizures with or without secondary generalisation).
- Off-Label Uses:
- Fibromyalgia.
- Generalised anxiety disorder (GAD).
- Restless legs syndrome (RLS).
- Migraine prophylaxis.
3. Dosage
- Adults:
- Neuropathic pain: Start with 300 mg once daily, titrate up to 300 mg 3 times daily (maximum: 3600 mg/day).
- Epilepsy: Start with 300 mg once daily, titrate up to 300 mg 3 times daily. Adjust based on response (maximum: 3600 mg/day).
- Elderly:
- Start with the lowest dose (e.g., 100–300 mg daily) and titrate slowly due to reduced renal clearance.
- Children (≥6 years):
- Epilepsy: Start with 10–15 mg/kg/day in 3 divided doses. Titrate up to 25–35 mg/kg/day.
4. Administration
- Take orally with or without food.
- Space doses evenly throughout the day (e.g., every 8 hours for three times daily dosing).
- Do not abruptly discontinue; taper dose gradually over at least one week to prevent withdrawal symptoms.
5. Forms Available
- Capsules: 100 mg, 300 mg, 400 mg.
- Tablets: 600 mg, 800 mg.
- Oral solution: 50 mg/mL.
6. Side Effects
6.1. Common Side Effects
- Dizziness.
- Drowsiness.
- Fatigue.
- Ataxia (lack of coordination).
6.2. Less Common Side Effects
- Peripheral oedema.
- Dry mouth.
- Weight gain.
6.3. Rare but Serious Side Effects
- Suicidal thoughts or behaviours.
- Severe allergic reactions (e.g., angioedema).
- Respiratory depression (especially with concomitant opioids or in elderly patients).
7. Warnings
- Suicide Risk: Monitor for suicidal thoughts and behaviours, especially at the start of treatment.
- CNS Depression: Avoid activities requiring mental alertness (e.g., driving) if experiencing drowsiness or dizziness.
- Respiratory Depression: Risk is increased in patients using opioids or with underlying respiratory conditions.
8. Precautions
- Use cautiously in patients with:
- Renal impairment (dose adjustment required).
- History of substance abuse (gabapentin misuse has been reported).
- Concurrent CNS depressant use (e.g., alcohol, sedatives).
9. Interactions
- Drug-Drug Interactions:
- Opioids (e.g., morphine): Increased risk of respiratory depression and sedation.
- Antacids: Reduce gabapentin absorption; take gabapentin at least 2 hours after antacids.
- CNS depressants (e.g., benzodiazepines): Increased sedation and CNS depression.
- Drug-Food Interactions:
- No significant interactions, but alcohol may enhance drowsiness and dizziness.
10. Monitoring Parameters
- Pain relief or reduction in seizure frequency.
- Signs of CNS depression (e.g., excessive drowsiness, confusion).
- Mood changes or emergence of suicidal thoughts.
- Renal function (for dose adjustment in renal impairment).
11. Use in Children
- Approved for use in children aged 6 years and older for epilepsy.
- Not recommended for neuropathic pain in children due to insufficient evidence.
12. Use in Pregnancy
- Category C: Use only if benefits outweigh risks. Gabapentin crosses the placenta, and its effects on the foetus are not well-studied. Consult a healthcare provider before use.
13. Use in Elderly
- Safe for use, but start at the lowest dose due to increased risk of CNS side effects and reduced renal clearance.
14. Use in Kidney Disease
- Dose Adjustments for Renal Impairment:
Creatinine Clearance (mL/min) | Total Daily Dose (mg) |
---|---|
≥60 | 900–3600 mg |
30–59 | 400–1400 mg |
15–29 | 200–700 mg |
<15 or on dialysis | 100–300 mg (after dialysis) |
15. Use in Liver Disease
- No dose adjustment is required, as gabapentin is not metabolised in the liver.
16. Patient Counselling Points
- Take gabapentin as prescribed. Do not adjust the dose or stop suddenly without consulting your doctor.
- Report any unusual mood changes, suicidal thoughts, or increased anxiety to your doctor immediately.
- Avoid alcohol and other sedatives to reduce the risk of drowsiness or respiratory depression.
- Inform your doctor of all medications you are taking to avoid interactions.
- Gabapentin may cause dizziness or drowsiness; avoid driving or operating heavy machinery until you know how it affects you.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Neurontin | Pfizer | $50–100 (30 tablets, 300 mg) |
Gralise (ER Tablets) | Depomed | $200–300 (30 tablets, 600 mg) |
Generic Gabapentin | Various manufacturers | $10–20 (30 tablets, 300 mg) |
18. FAQs (15 Questions)
- What is gabapentin used for?
Gabapentin is used to treat neuropathic pain and as adjunctive therapy for epilepsy. - How does gabapentin work?
It binds to calcium channels in the nervous system, reducing nerve excitability and pain transmission. - How long does gabapentin take to work?
Pain relief may take a few days to weeks, while seizure control may require consistent dosing over several weeks. - Can gabapentin cause side effects?
Yes, common side effects include dizziness, drowsiness, and fatigue. - Is gabapentin addictive?
While not classified as an addictive drug, gabapentin misuse has been reported, especially in those with a history of substance abuse. - Can gabapentin be used during pregnancy?
Use only if the benefits outweigh the risks. Consult your doctor before use. - Can children take gabapentin?
Yes, it is approved for children aged 6 years and older for epilepsy. - How should gabapentin be taken?
Take as prescribed, with or without food, and space doses evenly throughout the day. - Can gabapentin cause weight gain?
Yes, weight gain is a possible side effect, though not common. - What should I do if I miss a dose?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - Can I drink alcohol while taking gabapentin?
Avoid alcohol, as it may enhance drowsiness and dizziness. - Does gabapentin interact with other medications?
Yes, it interacts with opioids, antacids, and CNS depressants. - Can gabapentin treat anxiety?
While not officially approved, gabapentin is sometimes used off-label for anxiety. - How should gabapentin be stored?
Store at room temperature, away from moisture and heat. - Can gabapentin be stopped abruptly?
No, taper the dose gradually to prevent withdrawal symptoms such as seizures or increased pain.