Chronic Inflammatory Demyelinating Polyradiculoneuropathy Medication

If associated conditions are identified (HIV infection, lupus, paraproteinemia, lymphoma), treat them accordingly. The mainstay of treatment is immunosuppressive or immunomodulatory intervention.

Class Summary

These agents include intravenous immunoglobulin (IVIg), plasmapheresis, prednisone, azathioprine, methotrexate, mycophenolate, cyclosporine, and cyclophosphamide. Their use is based on the proposed pathogenesis of CIDP as an immune-mediated condition.

The FDA designated the IVIg product Gamunex as an orphan drug (September, 2008) for chronic inflammatory demyelinating polyneuropathy (CIDP). Approval was based on a clinical trial^[2] that showed Gamunex effective at improving certain motor functions for up to 48 weeks after initial treatment compared with placebo. The Inflammatory Neuropathy Cause and Treatment scale (INCAT) was used to measure patients’ ability to perform tasks (eg, walking, motor hand tasks). Twenty-eight of 59 patients (47%) treated with Gamunex had significantly improved INCAT scores compared with 13 of 58 patients (22.4%) treated with placebo (25% difference; 95% CI 7-43%; p=0.006). Patients with improved INCAT scores participated in a follow-up trial for an additional 24 weeks; 86% who continued receiving Gamunex maintained their improved INCAT scores compared with 61% who received placebo during the follow-up trial.

Plasmapheresis

Two controlled and blinded studies have confirmed benefit of plasmapheresis. Proposed mechanism is removal of antibodies and complement components that are responsible for immune-mediated damage of peripheral nerves. Plasma removed from blood through method similar to dialysis. Requires 2 large-bore needles, one to remove whole blood and other to return blood cells with albumin and saline. Patients whose veins are not large enough for repeated needle insertions have double-lumen catheter placed, either Quinton catheter (can be kept in for few weeks) or Permacath (can remain inserted indefinitely). Has been shown to have similar efficacy as IVIg in treatment of CIDP.

Immunoglobulin, intravenous (Gamunex)

Multiple clinical trials establish efficacy. Solution for IV infusion that is composed mostly of heterogenous human IgG but also small amounts of IgA and IgM. Its proposed mechanism of action based on thought that IVIg contains random set of antibodies that would neutralize immune factors, causing damage to peripheral nerve in CIDP. Used in infectious diseases to provide immediate passive immunity in situations in which time constraints do not allow development of active immunity via vaccination. Also used to treat multiple immune-mediated conditions, such as idiopathic thrombocytopenic purpura, GBS, and myasthenia gravis.

Activates complement cascade and provides multitude of antibodies capable of neutralization of many microorganisms, toxins, viruses, and presumably autoantibodies. Latter mechanism possibly underlies effect in CIDP. Several studies showed significant benefit in CIDP; this makes it useful alternative to plasmapheresis. On average, improvement seen by day 10 and continues through day 42.

Serum half-life approximately 21-29 d. Patients usually require repeated treatments every few weeks or months to maintain remission or treat recurrences.

Prednisone (Deltasone, Orasone, Meticorten)

Oral corticosteroid that suppresses inflammation and immune responses by altering protein synthesis in cells. Naturally occurring hormone that crosses cell membranes to bind to cytoplasmic receptors. Some mechanisms of action in CIDP are altering mediator function at site of inflammation and suppressing immune response.

Controlled trial demonstrated efficacy of oral prednisone.

Azathioprine (Imuran)

Purine analog that decreases metabolism of purines and also may inhibit DNA and RNA synthesis. Reduces disability and symptoms of CIDP by suppressing immune-mediated damage to nerves. A small trial did not show any beneficial effect but data are insufficient to draw conclusions.

Mycophenolate (CellCept)

Prodrug for immunosuppressive agent mycophenolic acid. Inhibits lymphocyte purine synthesis by inhibiting enzyme inosine monophosphate dehydrogenase. Reports of efficacy but no large controlled trials.

Cyclosporine (Sandimmune, Neoral)

Cyclic polypeptide consisting of 11 amino acids; effective in many autoimmune conditions. Inhibits first phase of T cell activation and does not affect humoral immunity. By suppressing T cells, may inhibit cell-mediated nerve damage at site of inflammatory/immune reaction. Small trial showed efficacy but data still insufficient to draw conclusions.

Cyclophosphamide (Cytoxan)

Cell-cycle phase-nonspecific antineoplastic agent and immunosuppressant that acts as alkylating agent.

Class Summary

In patients with CIDP, a variety of medications is used for treatment of neuropathic pain. Antiepileptic medications are quite effective. The 2 most frequently used medications, gabapentin and carbamazepine, are described.

Gabapentin (Neurontin)

Known to effect to GABA, but exact binding site unknown. Also has effects on calcium channels. Mostly used for treatment of epilepsy and neuropathic pain; 100-, 300-, and 400-mg cap and 600- and 800-mg film-coated tab are available.

Carbamazepine (Tegretol)

Blocks use-dependent sodium channels and inhibits sustained repetitive firing as well as reduces posttetanic potentiation of synaptic transmission in spinal cord. Potent enzyme inducer that can induce own metabolism. Used as anticonvulsant and for treatment of neuropathic pain.

Available in chewable 100-mg tab, in tab of 200 mg, XR tab of 100, 200, and 400 mg, and as susp of 100 mg/5 mL.

Class Summary

These medications are used frequently for the treatment of neuropathic pain. The most traditionally used medication, amitriptyline, is discussed.

Amitriptyline (Elavil)

Tertiary amine TCA known to decrease reuptake of serotonin and norepinephrine. Has been used more than other newer TCAs and has more proven benefits, although other TCAs, such as desipramine and nortriptyline, are also quite potent and have fewer adverse effects.

Tab available in 10, 25, 50, 75, 100, and 150 mg.

Pregabalin (Lyrica)

Thought to have similar mode of action to gabapentin. Clinical trials have shown efficacy for diabetic neuropathy and shingles induced neuropathic pain.

Duloxetine (Cymbalta)

Duloxetine clinical trials have shown efficacy in diabetic neuropathy pain and for depression.

It is a selective serotonin and norepinephrine reuptake inhibitor.