What is the recommended dosing regimen of steroids, such as prednisone (corticosteroid), for viral myositis?

Steroid Dosing Regimen for Viral Myositis

For viral myositis, prednisone should be initiated at 0.5-1 mg/kg/day (typically 60-80 mg/day) with a gradual taper over several weeks depending on clinical response. 1

Initial Treatment Approach

Grade 2 (Moderate) Viral Myositis:

• Start prednisone at 0.5-1 mg/kg/day (60-80 mg daily as a single dose) 1
• Continue this dose for 2-4 weeks depending on clinical response
• Begin taper by reducing dose by 10 mg every 2 weeks until reaching 30 mg/day
• Then slow the taper to 5 mg every 2 weeks until reaching 20 mg/day
• Further slow to 2.5 mg every 2 weeks until completion
• At 10 mg/day, may slow further to 1 mg every 2-4 weeks until completed 1

Grade 3-4 (Severe) Viral Myositis:

• For severe weakness limiting self-care or with bulbar symptoms (dysphagia, dysarthria):
  • Start methylprednisolone 1-2 mg/kg IV or higher dose bolus 1
  • Consider hospitalization for patients with severe weakness or respiratory compromise
  • After initial control, transition to oral prednisone at 1 mg/kg/day with taper as above 1

Monitoring During Treatment

• Check CK and aldolase levels to monitor disease activity
• Assess muscle strength every 2-4 weeks during initial treatment
• Monitor for steroid-related adverse effects (hyperglycemia, hypertension, weight gain)
• Improvement should be noted within 2 weeks, with more complete response expected after 4 weeks 1

Steroid-Sparing Agents

Consider adding a steroid-sparing agent concurrently with initial steroid therapy:

• Methotrexate: Start at 15-25 mg weekly, increasing by 5 mg every 2 weeks to target dose
• Azathioprine: 2 mg/kg/day (check thiopurine methyltransferase level first)
• Mycophenolate mofetil: Alternative option if methotrexate or azathioprine not tolerated 1

Management of Refractory Cases

For patients not responding adequately to initial therapy:

• Consider IVIG therapy (slower onset of action) 1
• For persistent symptoms despite 4 weeks of treatment, consider rituximab 2
• TNF-α inhibitors may be beneficial, especially if associated fasciitis is present 1

Important Considerations

• Split dosing may be considered for patients with night pain when tapering below 5 mg daily 1
• Patients with bulbar symptoms or myocarditis require more aggressive treatment and close monitoring 1
• Steroid-related myopathy is a potential complication that can be difficult to distinguish from active myositis 3
• Pulsed oral dexamethasone (high-dose cycles) is an alternative with fewer side effects but may lead to earlier relapse compared to daily prednisolone 4

The evidence for corticosteroid use in viral myositis comes primarily from observational studies and expert consensus rather than large randomized controlled trials. However, the clinical response to corticosteroids is generally favorable, with improvement in muscle strength and reduction in inflammatory markers in most patients.