Is acyclovir (antiviral medication) effective in treating Bell's palsy?

Acyclovir for Bell's Palsy

Acyclovir alone should NOT be prescribed for Bell's palsy, but may be offered in combination with oral corticosteroids within 72 hours of symptom onset, though the added benefit is minimal and corticosteroids remain the cornerstone of treatment. 1, 2

Primary Treatment Recommendation

Oral corticosteroids are the only proven effective treatment for Bell's palsy and should be prescribed within 72 hours of symptom onset for patients 16 years and older. 1, 2 The recommended regimen is prednisolone 50 mg daily for 10 days or prednisone 60 mg daily for 5 days followed by a 5-day taper. 2

Evidence supporting corticosteroids is robust: 83% recovery at 3 months with prednisolone versus 63.6% with placebo, and 94.4% recovery at 9 months versus 81.6% with placebo. 2, 3

Antiviral Monotherapy: Strong Recommendation Against

Acyclovir or other antiviral agents should never be prescribed as monotherapy for Bell's palsy. 1, 2 The American Academy of Otolaryngology-Head and Neck Surgery explicitly states this as a strong recommendation against antiviral monotherapy. 1

The largest high-quality trial showed no benefit: 71.2% recovery with acyclovir versus 75.7% without acyclovir at 3 months (P=0.50), and 85.4% versus 90.8% at 9 months (P=0.10). 3

Combination Therapy: Optional with Minimal Benefit

Combination therapy with acyclovir plus corticosteroids may be offered as an option within 72 hours of symptom onset, but the benefit is small. 1, 2

The evidence for combination therapy is mixed:

• Some older studies suggested modest benefit, with combination therapy showing 96.5% complete recovery versus 89.7% with steroids alone 4, 5
• However, the highest quality and most recent trial (2007, New England Journal of Medicine) found no additional benefit: 79.7% recovery at 3 months with combination therapy versus 83.0% with prednisolone alone 3

The American Academy of Otolaryngology-Head and Neck Surgery guidelines classify combination therapy as an "option" rather than a recommendation, acknowledging that while the benefit is small, the risks are minimal. 1, 2

Practical Algorithm for Acyclovir Use

Within 72 hours of symptom onset:

• Always prescribe corticosteroids (prednisolone 50 mg daily for 10 days) 2
• May add acyclovir 400 mg orally five times daily for 10 days if patient and provider prefer combination therapy after shared decision-making 2
• Alternative: Valacyclovir can be used instead of acyclovir due to better bioavailability and less frequent dosing 2

Beyond 72 hours of symptom onset:

• Do not initiate corticosteroids or antivirals - no evidence supports benefit after this window 6
• Focus on eye protection and supportive care 6

Common Pitfalls to Avoid

• Never prescribe acyclovir alone - it is ineffective as monotherapy and delays appropriate corticosteroid treatment 1, 2, 3
• Do not overestimate the benefit of combination therapy - the most rigorous evidence shows no additional benefit over corticosteroids alone 3
• Do not initiate treatment beyond 72 hours - clinical trials demonstrating any benefit specifically enrolled patients within this window 6
• Do not neglect eye protection regardless of antiviral or steroid use - implement lubricating drops, ointments, and mechanical protection for patients with impaired eye closure 2

Special Populations

Children: Evidence for acyclovir benefit in pediatric Bell's palsy is even weaker than in adults, and children have better spontaneous recovery rates. 2 Antiviral therapy should generally be avoided in this population. 2

Pregnant women: Treatment decisions should be individualized with careful risk-benefit assessment, though corticosteroids remain the primary consideration rather than antivirals. 2

Bottom Line

Corticosteroids are the only proven treatment for Bell's palsy. 1, 2, 3 Acyclovir adds minimal to no benefit when combined with steroids and should never be used alone. 1, 3 The decision to add acyclovir to corticosteroids is optional and should involve shared decision-making, recognizing that the highest quality evidence does not support additional benefit. 1, 3