Microscopic polyangiitis responds well to treatment with glucocorticoids such as prednisone together with an immunosuppressant such as cyclophosphamide. The combination of these 2 drugs decreases the remission of Microscopic polyangiitis by about 90%.

• Pharmacologic medical therapies for Microscopic polyangiitis include glucocorticoids and immunosuppressant.^[1][2]

• In more aggressive forms of the disease prednisone is interchanged with methylprednisolone.^[3][4]
• Both mild and severe forms of the disease are administered together with cyclophosphamide which is given in intravenous pulses every 2 weeks.
• After the first 3 doses, cyclophosphamide is administered every 3 weeks.
• Cyclophosphamide can also be given orally at a dose of 2 mg/kg/day, however, more side effects are seen with the oral dose, such as neutropenia.
• The dose of prednisone that is given is 1 mg/kg/day for less aggressive forms of the disease.

• If Microscopic polyangiitis is severe, plasmapheresis may also be given in conjunction with an immunosuppressant and glucocorticoid.
• Plasmapheresis has been shown to have benefit in patients with pulmonary and renal involvement.
  • Preferred regimen (1): Methylprednisolone 1g/kg 3 times a day.
  • Preferred regimen (2): Cyclophosphamide 15 mg/kg.

• Induction therapy using rituximab and glucocorticoids in a recent study conducted by RITUXVAS compared rituximab and cyclophosphamide.^[5][6]
• The trial showed no superiority, in that both medications were effective at inducing remission. However, the safety and the long term use of rituximab needs to be further addressed.

• The maintenance therapy for Microscopic polyangiitis is with azathioprine, which is less toxic to that of cyclophosphamide. Azathioprine is administered for 18 months.
  • Preferred regimen (1):Azathioprine 1 to 2 mg/kg/day.

• Other medications that may be used as maintenance are:
  • Preferred regimen (1): Mycophenolate mofetil up to 1g twice a day.
  • Preferred regimen (2): Methotrexate: 0.3 to 25 mg/kg/week.