Background: Post Herpetic neuralgia (PHN) is neuropathic pain that occurs after herpes zoster infection. Several treatments have been suggested in the management of PHN. This study evaluates the efficacy of subcutaneous injection of botulinum toxin in patients suffering from PHN.

Methods: Nineteen patients suffering from PHN for more than 2 months were enrolled in the study. The severity of pain was assessed by visual analog scale (VAS). A total dose 500 units of BTX-A was injected around the site of pain. This was administered in about 25 sub-cutaneous injection around the site, delivering approximately 20U/ml of BTX-A per injection. The patients were followed at 1,2, 3,4,12 and 16 weeks after the administration of the drug.

Results: The mean age was 56 years (age range 36 to 63) for non-pregnant patients. The two pregnant patients of age 28 and 32 year old who were in their 28 and 30 weeks of gestation were also included. The mean duration of PHN was 4.78 wks. At each visit VAS was used to evaluate the degree of pain (0: painless; 10: maximum pain). There was a significant reduction in the severity of pain after the injection.

Conclusions: Botulinum toxin significantly decreases the severity of pain in PHN patients and last for 4-6 month of the period. This decrease is less prominent by passing time.