Background: Postpoliomyelitis syndrome (PPS) is likely due to degeneration and dysfunction of terminal axons of enlarged postpolio motor units. Age-related decline in growth hormone and insulin-like growth factor (IGF-I) may be a contributing factor. Neuromuscular junction abnormalities and decreased IGF-I levels may respond to the anticholinesterase pyridostigmine, with consequent improvement in strength, fatigue, and quality of life.
Objectives: To determine the effect of pyridostigmine in PPS on health-related quality of life, isometric muscle strength, fatigue, and serum IGF-I levels; and to assess the safety of pyridostigmine in PPS.
Methods: The study was a multicenter, randomized, double-blinded, placebo-controlled trial of a 6-month course of pyridostigmine 60 mg three times per day in 126 PPS patients. The primary data analysis compared mean changes of outcomes between treatment and control groups at 6 months using an intention to treat approach. Secondary analyses included a comparison of outcomes at 6 and 10 weeks, and in compliant patients.
Results: The study showed no significant differences in pyridostigmine and placebo-treated patients with regard to changes in quality of life, isometric strength, fatigue, and IGF-I serum levels at 6 months in the primary analysis and in compliant patients. There were no differences in outcomes at 6 and 10 weeks between groups. However, very weak muscles (1 to 25% predicted normal at baseline) were somewhat stronger (p = 0.10, 95% CI of difference -9.5 to 73.3%), and in compliant patients IGF-I was somewhat increased (p = 0.15, 95% CI of difference -6.4 to 44.8 ng/mL) at 6 months with the medication. Pyridostigmine was generally well tolerated.
Conclusions: This study showed no significant differences between pyridostigmine and placebo-treated PPS patients on measures of quality of life, isometric strength, fatigue, and serum IGF-I.