Abstract
Background
Duchenne muscular dystrophy (DMD) is a progressive muscle condition starting in childhood, leading to severe disability and a shortened life span. It is due to severe deficiency of the protein dystrophin which performs both structural and signalling roles within skeletal and cardiac myocytes. Calcium accumulates in dystrophic muscle cells and plays a role in cell damage. It has been hypothesised that use of calcium antagonists might reduce this calcium load and its toxic effect on muscle cells. This is an updated review, in which no new trials were found.
Objectives
To evaluate the effects of calcium antagonists on muscle function and muscle strength in people with DMD.
Search methods
We searched the Cochrane Neuromuscular Disease Group Trials Register (July 2010), MEDLINE (from January 1950 to July 2010) and EMBASE (from January 1947 to July 2010). We also searched bibliographies in reports of any trials.
Selection criteria
All randomised or quasi-randomised controlled trials of any calcium antagonist in people with DMD.
Data collection and analysis
Both authors assessed all identified trials for inclusion in the study on the basis of whether they fulfilled the selection criteria. Both authors extracted data from the trials and assessed the methodological quality. Had there been more than one trial of the same intervention and outcome of sufficient methodological quality, we had planned to undertake a meta-analysis.
Main results
Five randomised or quasi-randomised double-blind trials fulfilled the selection criteria, but were not sufficiently comparable to undertake a meta-analysis. The drugs studied were verapamil (8 participants), diltiazem (56 participants), nifedipine (105 participants) and flunarizine (27 participants). There were limitations in the description of blinding and randomisation, and definition of outcome measures. One trial, using verapamil, showed a difference between groups in muscle force measured by ergometry, but also revealed cardiac side effects. The numbers of people included in the trials were low, and so the studies may not have included enough people for sufficient power to detect small differences in muscle force or function between placebo and control groups. In addition, calcium antagonists were in an early stage of development and some of the second generation drugs that have a better side effect profile, such as amlodipine, have not been studied.
Authors’ conclusions
There is no evidence to show a significant beneficial effect of calcium antagonists on muscle function in DMD.
Plain language summary
Calcium channel blocking drugs for Duchenne muscular dystrophy
Duchenne muscular dystrophy is a progressive wasting condition of muscles which starts in early childhood, leads to dependence on a wheelchair by the age of thirteen and respiratory failure by late teens. The condition is due to absence of dystrophin, a large muscle protein that has several functions within muscle cells. We know that calcium molecules build up in the muscle cells of people with Duchenne muscular dystrophy and this is associated with cell death. The rationale behind this review was to ascertain whether randomised controlled trials using drugs that block calcium entry into muscle would result in a reduction in progression of the condition. Although these trials were conducted over ten years ago a systematic review was not done at that time, and so a potential effect of calcium blocking drugs (antagonists) on the course of DMD may have been missed. If it were to exist, calcium antagonists might be an effective treatment in their own right or, more likely, could be used in combination with newer treatments such as corticosteroids or potential treatments such as gene related therapies.
This is an updated review. In the original review original eight studies were identified and five were high enough quality to be included. In this update no new trials were identified and so five were still included in the review. These studies were of different types of calcium channel blocking drugs and measured a variety of outcomes such as muscle strength, scales of muscle function, biochemical changes in muscle and electrocardiographic findings. Only one study showed a beneficial effect, which was an increase in muscle strength, but in this study the drug used was also associated with cardiac side effects. Adverse effects noted were mostly known side effects of calcium channel blockers.
Limitations of the review were that a meta-analysis could not be done as the trials used different calcium channel blockers and measured different outcomes, and all but one of the trials included a low number of patients. In conclusion, the review did not find calcium antagonists to have a useful effect.
