Table 1 Patient eligibility criteria for assessment of the efficacy of gabapentin in prevention of postherpetic neuralgia

Male or female, at least 50 years old

Patients taking gabapentin or a tricyclic antidepressant

Patients with diagnoses of uncomplicated herpes zoster presenting within the first 72 h of vesicle formation and an average pain score of at least 4 on a visual analogue scale of pain before therapy

Patients with evidence of cutaneous or visceral dissemination of herpes zoster infection (cutaneous dissemination is defined as more than 20 discrete lesions outside adjacent dermatomes) or ocular involvement of herpes zoster

Patients who are willing and able to comply with the requirements of the study

Patients with histories of intolerance or hypersensitivity to any active components of or excipient from the study drugs

Patients who are willing and able to give written informed consent

Patients with severe hepatic impairment or impaired renal function (creatinine clearance <79 ml/minute)

Patients who have received cytotoxic drugs or immunosuppressive therapy within the previous 3 months (e.g., long-term systemic corticosteroids)

Patients with any diagnosed immune dysfunction

Patients who have received immunomodulatory medications (including interferon) within the previous 4 weeks

HZ vaccine immunization