Gabapentin (canadian Neurontin Oral Solution)
Manufacturer: Pfizer, New York, NY
Indications: Neurontin is indicated for the management of postherpetic neuralgia (PHN) in adults. Drug Class: Gabapentin, 1-(aminomethyl)cyclohexaneacetic acid, is structurally related to the neurotransmitter GABA (gamma aminobutyric acid) but does not modify GABAA or GABAB radioligand binding and does not inhibit GABA uptake or degradation.
Uniqueness of Drug: Gabapentin represents a novel class of antihyperalgesic agents. It decreases substance P activity, and its mechanism might involve stimulation of the neuronal GABAg1,g2 receptors negatively coupled to voltage-dependent calcium channels, thereby lessening pain signals to the brain. However, its mechanism of action is unknown at this time. Precautions: The total number of subjects treated with gabapentin in controlled clinical trials in patients with PHN was 336, of whom 102 (30%) were between ages 65 and 72, and 168 (50%) were age 75 or older. The most commonly observed adverse effects observed with the use in adults, not observed with equal frequency in placebo-controlled treated patients, were dizziness, somnolence, and peripheral edema. Treatment-emergent side effects, observed in at least 1% of patients with PHN who received gabapentin and more numerous than in the placebo-treated patients, were diarrhea, dry mouth, constipation, vomiting, ataxia, thinking abnormalities, abnormal gait, incoordination, blurred vision, and conjunctivitis. There were no clinically important differences between men and women in the types and incidence of adverse effects. Dosage: Gabapentin is supplied in capsules of 100, 300, and 400 mg and as an oral solution. It may be initiated as a single 300-mg dose on day 1, 600 mg/day dose on day 2 (divided twice daily), and 900 mg/day dose on day 3 (divided thrice daily). The dose can subsequently be titrated up as needed for pain relief to a daily dose of 1800 mg (thrice daily). In controlled clinical trials, efficacy was observed over a range of doses from 1800 to 3600 mg/day, with comparable effects across the dose range. No additional benefit was demonstrated by using doses greater than 1800 mg/day.
P&T Committee Considerations: Gabapentin is an anticonvulsant previously approved as an adjunct treatment for partial epileptic seizures in adults and children. It is also indicated for the adjunctive treatment of epilepsy and a range of neuropathic pain conditions. It is now approved in the U.S. for the management of PHN. Gabapentin medication is the first oral medication approved by the FDA for this indication. The pain associated with PHN is extremely intense and, once established, can last for years. In the U.S., there are over one million new cases of herpes zoster each year. PHN is a syndrome of often intractable pain that persists after the resolution of herpes zoster, a condition commonly known as shingles. This intense pain is described as burning, deep aching, tearing, and electric shock-like. Approximately 10% to 15% of all patients with herpes zoster develop PHN, which can persist for years. It is recommended that gabapentin be placed on the hospital formulary for treating patients with PHN. The average wholesale price for the 100-, 300-,and 400-mg capsule are $52.95/100, $132.38/100 and $158.84/100, respectively. The average wholesale price for the 470-ml oral solution is $100.69.