Gabapentin

Generic name: Gabapentin
Brand name: Neurontin

Indications

Gabapentin is indicated for the treatment of postherpetic neuralgia and epilepsy.

Dosage and Administration

Neurontin (gabapentin) capsules, tablets and oral solution are available as 100 mg, 300 mg and 400 mg capsules; 600 mg and 800 mg tablets; and 250 mg/5 ml oral solution.

Normal Dosage:

Postherpetic Neuralgia
In adults with postherpetic neuralgia, Neurontin therapy may be initiated as a single 300-mg dose on Day 1, 600 mg/day on Day 2 (divided BID), and 900 mg/day on Day 3 (divided TID). The dose can subsequently be titrated up as needed for pain relief to a daily dose of 1800 mg (divided TID).

Epilepsy

Patients > 12 years of age: The effective dose of Neurontin is 900 to 1800 mg/day and given in divided doses (three times a day) using 300 or 400 mg capsules, or 600 or 800 mg tablets. The starting dose is 300 mg three times a day. If necessary, the dose may be increased using 300 or 400 mg capsules, or 600 or 800 mg tablets three times a day up to 1800 mg/day.

Pediatric Patients Age 3-12 years: The starting dose should range from 10-15 mg/kg/day in 3 divided doses, and the effective dose reached by upward titration over a period of approximately 3 days. The effective dose of Neurontin in patients 5 years of age and older is 25-35 mg/kg/day and given in divided doses (three times a day). The effective dose in pediatric patients ages 3 and 4 years is 40 mg/kg/day and given in divided doses (three times a day)

Overdose: Overdose symptoms include double vision, drowsiness, slurred speech, diarrhea, poor coordination, and difficulty in breathing.

Drug Description

Gabapentin is described as 1-(aminomethyl)cyclohexaneacetic acid with a molecular formula of C9H17NO2 and a molecular weight of 171.24. The structural formula of gabapentin is:

Gabapentin is a white to off-white crystalline solid with a pKa1 of 3.7 and a pKa2 of 10.7. It is freely soluble in water and both basic and acidic aqueous solutions. The log of the partition coefficient (n-octanol/0.05M phosphate buffer) at pH 7.4 is -1.25.

Side effects

The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

• Very common (affect more than 1 in 10 people)
• Sleepiness or fatigue.
• Fever.
• Dizziness.
• Shaky movements and unsteady walk (ataxia).

Common (affect between 1 in 10 and 1 in 100 people)

• Infections.
• Decrease in the number of white blood cells in the blood (leucopenia).
• Changes in appetite.
• Unstable moods (emotional lability).
• Confusion, loss of memory (amnesia).
• Depression.
• Anxiety or nervousness.
• Difficulty sleeping (insomnia).
• Headache.
• Tremor or twitching.
• Changes in sensation, for example pins and needles or numb sensations.
• Visual disturbances.
• Raised blood pressure (hypertension).
• Shortness of breath, cough.
• Gut disturbances such as dry mouth, indigestion, nausea, vomiting, constipation, diarrhoea or abdominal pain.
• Small haemorrhage (bleeding) in the skin (purpura), often seen as bruises.
• Skin reactions such as rash, itching or acne.
• Swelling of the legs, ankles or face due to excess fluid retention (oedema).
• Impotence.

Precautions

• Use caution when driving, operating machinery, or performing other hazardous activities.
• Avoid alcohol during treatment. Alcohol may increase the risk of having side effects and may reduce the effectiveness of this drug.
• Before taking Gabapentin, tell your doctor if you have any other medical conditions, especially kidney, liver, or heart disease.
• Gabapentin belongs to the FDA pregnancy category C. This means that it is not known whether Gabapentin will be harmful to an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant or could become pregnant during treatment.

Drug Interactions

• Does not interact with other commonly used antiseizure medications.
• Antacids will decrease the amount of Gabapentin that is absorbed in the stomach. Do not take Gabapentin for at least 2 hours after a dose of antacid.
• May increase the effects of other drugs that cause drowsiness, including antidepressants, alcohol, antihistamines, sedatives (used to treat insomnia), pain relievers, anxiety medicines, and muscle relaxants.

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