Key Points
- CIDP is viewed as the chronic form of Guillain-Barre syndrome
- CIDP can strike any age and either sex
- Early treatment is crucial
- Gamunex is already approved for treatment of PI and ITP
Patients with chronic inflammatory demyelinating polyneuropathy (CIDP) finally have a treatment option that has been recognized
by the U.S. Food and Drug Administration (FDA). Gamunex, an intravenous immune globulin (IVIG) pooled from human blood, recently
received FDA approval for the treatment of CIDP.
The product was previously approved for primary humoral immunodeficiency disease (PI) and idiopathic thrombocytopenic purpura
(ITP). Although various immune globulins have been used over the years to treat CIDP on an off-label basis, Gamunex is the
first product to receive FDA approval as an orphan drug for this indication. The orphan-drug designation provides manufacturers
with financial incentives to develop treatments for rare diseases, defined as those affecting fewer than 200,000 people in
the United States.
CIDP is a rare autoimmune disorder characterized by progressive weakness and impaired sensory function in the legs and arms.
The disorder, also known as chronic relapsing polyneuropathy, is caused by damage to the myelin sheath (the fatty covering
that protects nerve fibers) of the peripheral nerves. CIDP is closely related to Guillain-Barré syndrome and is considered
the chronic counterpart of that acute disease. Although it is typically more prevalent in young adults and in men, it can
strike at any age and in either gender. The course of CIDP varies widely among patients, but many patients are left with residual
numbness, weakness, fatigue, and other symptoms which can lead to reduced quality of life.
CIDP typically goes unrecognized and untreated due to its heterogeneous presentation and diagnostic limitations. However,
early treatment is crucial in preventing irreversible loss of nerve axons and improving functional recovery. Traditional treatment
options for CIDP have included corticosteroids, which may be prescribed alone or in combination with immunosuppressant drugs,
plasmapheresis, and IVIG. Theories about how to treat this condition include the hypothesis that Gamunex helps improve muscle
function in patients with CIDP by modulating the immune system's response to the inflammation that damages the myelin sheaths,
but the exact mechanism remains unknown. "Research in this field is lacking, and the approval of Gamunex signals a step forward
for patients suffering from CIDP," said Tarun Verma, PharmD, BCPS, Pharmacy Clinical Manager of Florida Hospital-Fish Memorial.
Gamunex was approved for administration as a total loading dose of 2 g/kg, given in divided doses over two to four consecutive
days. For maintenance infusions, Gamunex may be administered either over one day at a dose of 1 g/kg or divided into two doses
of 0.5 g/kg over two consecutive days. The dose is typically repeated every three weeks. Gamunex, which is available as a
10 percent liquid, is incompatible with saline but can be diluted with 5 percent dextrose in water (D5W).
Side effects reported most frequently by patients were headache, fever, increased blood pressure, rash, joint pain, chills,
back pain, nausea, and lightheadedness. Similar to other licensed IGIV products, Gamunex holds a black box warning about renal
dysfunction, acute renal failure, osmotic nephrosis, and death in predisposed patients. Therefore, blood urea nitrogen, serum
creatinine, and urine output should be closely monitored in patients at risk of developing renal failure. Renal dysfunction
and acute renal failure have been reported more frequently in patients receiving IGIV products containing sucrose, which is
typically used as a stabilizer.
MONA NASHED is a writer and hospital pharmacist in New Jersey.
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