Neurontin Clinical Pharmacology

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Neurontin - Clinical Pharmacology [Gabapentin]

The normalized CL/ F values observed in pediatric patients 5 years of age and older were consistent with values observed in adults after a single dose. The oral volume of distribution normalized per body weight was constant across the age range. These pharmacokinetic data indicate that the effective daily dose in pediatric patients with epilepsy ages 3 and 4 years should be 40 mg/ kg/ day to achieve average plasma concentrations similar to those achieved in patients 5 years of age and older receiving gabapentin at 30 mg/ kg/ day (see DOSAGE AND ADMINISTRATION).

Gender

Although no formal study has been conducted to compare the pharmacokinetics of gabapentin in men and women, it appears that the pharmacokinetic parameters for males and females are similar and there are no significant gender differences.

Race

Pharmacokinetic differences due to race have not been studied. Because gabapentin is primarily renally excreted and there are no important racial differences in creatinine clearance, pharmacokinetic differences due to race are not expected.

Clinical Studies

Postherpetic Neuralgia
Neurontin Ž was evaluated for the management of postherpetic neuralgia (PHN) in 2 randomized, double-blind, placebo-controlled, multicenter studies; N= 563 patients in the intent-to-treat (ITT) population (Table 1). Patients were enrolled if they continued to have pain for more than 3 months after healing of the herpes zoster skin rash.

TABLE 1. Controlled PHN Studies: Duration, Dosages, and Number of Patients
Study Study Duration Gabapentin (mg/ day)
Target Dose
Patients Receiving
Gabapentin
Patients Receiving
Placebo 1 8 weeks 3600 113 116
2 7 weeks 1800, 2400 223 111 Total 336 227
a Given in 3 divided doses (TID)

Each study included a 1-week baseline during which patients were screened for eligibility and a 7-or 8-week double-blind phase (3 or 4 weeks of titration and 4 weeks of fixed dose). Patients initiated treatment with titration to a maximum of 900 mg/ day gabapentin over 3 days. Dosages were then to be titrated in 600 to 1200 mg/ day increments at 3-to 7-day intervals to target dose over 3 to 4 weeks.