Gabapentin: Price, Dosage & Where to Buy

Gabapentin is a gabapentinoid medicine that acts as an alpha2-delta calcium-channel ligand. It requires a prescription in the United Kingdom.

Gabapentin is prescribed for the management of postherpetic neuralgia in adults and as adjunctive therapy in the treatment of partial onset seizures, with and without secondary generalisation, in adults and children aged 3 years and older with epilepsy. Generic gabapentin has been available since September 2003.

Gabapentin belongs to the gabapentinoid class of medicines. It binds to the alpha2-delta subunit of voltage-gated calcium channels in the central nervous system. By attaching to this subunit, gabapentin modulates the release of certain neurotransmitters that are involved in transmitting pain signals and in the abnormal electrical activity that causes seizures.

This action is thought to reduce the perception of pain in conditions such as postherpetic neuralgia and to decrease the likelihood of seizures when used with other antiepileptic drugs. The precise way gabapentin produces its therapeutic effects is not fully understood, but its interaction with calcium channels in nerve tissue is believed to be central to its mechanism.

Gabapentin is indicated for the management of postherpetic neuralgia in adults. Postherpetic neuralgia is nerve pain that persists after a shingles infection has healed. Gabapentin is also indicated as adjunctive therapy in the treatment of partial onset seizures, with and without secondary generalisation, in adults and paediatric patients 3 years of age and older with epilepsy.

Adjunctive therapy means that gabapentin is used alongside other antiepileptic medicines to help control seizures that begin in one part of the brain. These seizures may remain localised or spread to involve the entire brain.

The label lists capsules in strengths of 100 mg, 200 mg, 300 mg, and 400 mg, oral solutions of 50 mg/mL and 250 mg/5 mL, oral suspensions of 250 mg/5 mL, and tablets in strengths of 100 mg, 300 mg, 400 mg, 450 mg, 600 mg, 750 mg, 800 mg, and 900 mg. For postherpetic neuralgia in adults, gabapentin may be initiated on Day 1 as a single 300 mg dose, on Day 2 as 600 mg/day (300 mg two times a day), and on Day 3 as 900 mg/day (300 mg three times a day). The dose can subsequently be titrated up as needed for pain relief to a dose of 1800 mg/day (600 mg three times a day).

For epilepsy with partial onset seizures in patients 12 years of age and above, the usual starting dose is 300 mg three times a day. The recommended maintenance dose is 300 mg to 600 mg three times a day.

For paediatric patients aged 3 to 11 years, the starting dose range is 10 mg/kg/day to 15 mg/kg/day, given in three divided doses. Dose adjustment is recommended in patients with renal impairment.

Gabapentin capsules should be stored at 20 degrees to 25 degrees Celsius (68 degrees to 77 degrees Fahrenheit), with excursions permitted between 15 degrees and 30 degrees Celsius (59 degrees to 86 degrees Fahrenheit). This corresponds to controlled room temperature as defined in standard references. The capsules should be kept in their original container to maintain quality and should be stored away from excessive heat and moisture.

If a dose of gabapentin is missed, it should be considered in the context of the regular dosing schedule. For postherpetic neuralgia, gabapentin is typically dosed three times a day, and for epilepsy, it is also given three times daily with a maximum interval of 12 hours between doses. Missing a dose may reduce the medicine's effectiveness in controlling pain or preventing seizures.

Patients are generally advised not to double the next dose to make up for a missed one. The prescriber or pharmacist can provide specific guidance based on the individual treatment plan and how much time has passed since the missed dose.

Observational studies have not indicated an increased risk of major birth defects or miscarriage with gabapentin use during pregnancy, though these studies have methodological limitations. In animal studies, gabapentin was developmentally toxic when given to pregnant animals at doses similar to or lower than those used clinically. Postmarketing data suggest that extended gabapentin use with opioids close to delivery may increase the risk of neonatal withdrawal compared to opioids alone.

Neonatal withdrawal signs reported have included tachypnoea, vomiting, diarrhoea, hypertonia, irritability, sneezing, poor feeding, hyperactivity, abnormal sleep pattern, and tremor. Women who are pregnant or planning pregnancy should discuss the risks and benefits of gabapentin with their doctor. Gabapentin is secreted in human milk following oral administration.