Chronic inflammatory demyelinating polyradiculoneuropathy ( CIDP ) is a disease causing progressive or relapsing and remitting weakness and numbness. It is probably due to an autoimmune process. Immunosuppressive or immunomodulatory drugs would be expected to be beneficial.
A study has systematically reviewed the evidence from randomised trials of immunomodulatory and immunosuppressive agents other than corticosteroids, immunoglobulin and plasma exchange for CIDP.
Researchers wanted to measure the change in disability after one year as our primary outcome. The secondary outcomes were change in disability after four or more weeks ( from randomisation ), change in impairment after at least one year, change in maximum motor nerve conduction velocity and compound muscle action potential amplitude after one year and for those participants who were receiving corticosteroids or intravenous immunoglobulin, the amount of this medication given during at least one year after randomisation.
Participants with one or more serious adverse events during the first year was also a secondary outcome.
Four trials fulfilled the selection criteria, one of Azathioprine ( 27 participants ), two of Interferon beta-1a ( 77 participants in total ) and one of Methotrexate ( 60 participants ).
The risk of bias in the two trials of Interferon beta-1a for CIDP and the trial of Methotrexate was assessed to be low but bias in the trial of Azathioprine was judged high.
None of these trials has shown significant benefit in the primary outcome ( measured only in the Methotrexate study ) or secondary outcomes selected for this review.
Severe adverse events occurred no more frequently than in the placebo groups for Methotrexate and Interferon beta-1a, but participant numbers were low.
There was no adverse event reporting in the Azathioprine study.
In conclusion, the evidence from randomised trials did not show significant benefit from Azathioprine, Interferon beta-1a or Methotrexate but none of the trials was large enough to rule out small or moderate benefit.
The evidence from observational studies is insufficient to avoid the need for randomised controlled trials to discover whether these drugs are beneficial.
Future trials should have improved designs, more sensitive outcome measures and longer durations. ( Xagena )
Mahdi-Rogers M et al, Cochrane Database Syst Rev. 2013;6:CD003280. doi: 10.1002/14651858.CD003280.pub4.