Multiple sclerosis (MS) is a disease that affects young and middle-aged adults, causing different symptoms in individuals. It is caused by damage to the myelin sheaths (fibres that wrap around and protect the nerves and spinal cord). Potassium (a mineral) is important for nerve function, but may become too active when there is not enough myelin. Potassium blocking drugs (4-aminopyridine AP, and 3,4-daminopyridine DAP) may be able to improve nerve function in nerves without enough myelin. However, the review of trials found there is not enough evidence about the safety of these drugs or whether benefits are certain.
Currently available information allows no unbiased statement about safety or efficacy of aminopyridines for treating MS symptoms. Furthermore, we could not obtain any data on three unpublished RCTs (more than 300 participants). We conclude that publication bias remains a pervasive problem in this area, and that until the results of these unpublished studies are available to the scientific community, no confident estimate of effectiveness of aminopyridines in the management of MS symptoms is possible.
The potassium channel blockers 4-aminopyridine (AP) and 3,4-diaminopyridine (DAP) increase nerve conduction in demyelinated nerve fibers, and have been proposed as a symptomatic therapy for people with multiple sclerosis (MS).
To determine the efficacy and safety of aminopyridines for neurological deficits in adults with MS.
We searched the Cochrane MS Group trials register (December 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 4, 2004), MEDLINE (January 1966 to December 2004) and EMBASE (1974 to December 2004). We hand searched bibliographic references from retrieved studies and recent MS symposia reports, and contacted known studies' investigators.
We included trials fulfilling all following criteria: randomised controlled trials (RCTs); adults with MS, out of exacerbation; AP or DAP treatment versus placebo; clinical endpoints.
Three reviewers independently extracted data and assessed trial quality from 17 full-paper studies.
Six studies (eight publications, 198 participants, all crossover trials) were considered. Five studies assessed the efficacy of AP versus placebo, one compared DAP with active placebo. Treatment duration ranged from hours to six months. Median quality score of the studies was three.
Of the 198 treated participants, there were six major side effects: one acute encephalopathy, three episodes of confusion, and two seizures.
Three studies (54 participants) assessed manual muscle testing, with 29 participants (54%) improving in at least one muscular district during study treatment versus four participants (7%) during placebo (odds ratio [OR] 14.5, 95% confidence interval [CI] 4.7 to 43.7). Nine out of 54 participants (17%) improved in ambulation during study treatment versus none during placebo (p < 0.001). A lower Expanded Disability Status Scale (EDSS) score was found in 13/198 participants during study treatment (7%) versus none during placebo (p < 0.001). No improvement in neuropsychological tests was found in three trials assessing cognitive function. Finally, 47/136 adults with MS (35%) felt better when receiving the study drug, against 7(5%) on placebo (OR 9.7, 95% CI 4.3 to 22.0).