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Acyclovir was not shown to be effective in Bell's palsy

Three Part Question

In [an adult patient with Bell's palsy] does [acyclovir] improve [functional recovery]?

Clinical Scenario

A 45 year old man presents to the emergency department with a one day history of left-side facial weakness. Physical examination confirms that the patient has an incomplete left-sided Bell's palsy. As prednisone has a limited role in improving the recovery of incomplete Bell's palsy and medical literature postulates a viral etiology in Bell's palsy, you wonder whether acyclovir would improve the outcome for this patient.

Search Strategy

Medline 1966-04/02 using the OVID interface. Cochrane Library, Issue 1 2002.
Medline: [exp Bell palsy or exp Facial paralysis OR exp Facial nerve OR bell OR bells OR (facial adj5 palsy).af OR (facial adj5 paralysis).af OR (facial adj5 weakness).af] AND [exp Acyclovir or OR] LIMIT to Human AND English language. Cochrane: (Bell palsy)

Search Outcome

Altogether 49 papers were found of which 2 were relevant and had been included in a systematic review by the Cochrane Neuromuscular Disease Group (3). A meta-analysis was not performed, as the 2 studies were not directly compatible. This review was last updated on the 19th November 2001. No further relevant papers were identified after this date.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Adour KK et al,
119 patients presented within the first 72 hours Acyclovir & prednisolone v placebo & prednisolone Acyclovir 2000mg per day for 10 days Prednisolone 1 mg/kg for 5 days tapered to 10 mg/day for next 5 daysPRCTElectrical testingAcyclovir & prednisolone group had less partial nerve degeneration (p=0.05)Small study 20% patients (16.8%) were lost to follow-up No intention to treat analysis
Visual assessment of motor recovery by FPRP & FPRISmall treatment effect was demonstrated in the acyclovir & prednisolone group (p=0.04)
De Diego JI et al,
113 patients presenting within the first 96 hours Acyclovir alone v prednisolone alone Acyclovir 2400mg per day for 10 days Prednisolone 1mg/kg for 10 days tapered to zero over the next 6 daysPRCTElectrical testing Prednisone had less degeneration of marginal branch of facial nerve (p=0.02)Small study No real placebo control group 12 patients (10.6%) were lost to follow-up No intention to treat analysis
Visual assessment of motor recovery by FPRPPrednisone was beneficial (p=0.0338)


The results from the Adour trial suggest that treatment with acyclovir & prednisolone is more effective than treatment with prednisolone alone. However, the results from the De Diego trail suggest that treatment with prednisolone alone is more effective than treatment with acyclovir alone. Both studies are small and a significant number of patients were lost to follow-up in each. A large PRCT with a real placebo control group is needed to clarify the effectiveness of acyclovir in the treatment of Bell's palsy.

Clinical Bottom Line

Current evidence does not support the use of acyclovir alone in Bell's palsy. The combination of acyclovir and prednisone may have a small benefit in the final functional recovery.

Level of Evidence

Level 3 - Small numbers of small studies or great heterogeneity or very different population.


  1. Adour KK, Ruboyianes JM, Von Doersten PG, et al. Bell's palsy treatment with acyclovir and prednisone compared with prednisone alone: A double-blind, randomized, controlled trial. Ann Otol Rhinol Laryngol 1996;105(5):371-378.
  2. De Diego JI, Prim MP, De Sarria MJ, et al. Idiopathic Facial Paralysis: A randomized, prospective and controlled study using single-dose prednisone versus acyclovir three times daily. Laryngoscope 1998;108(4):573-575.
  3. Sipe J, Dunn L. Acyclovir for Bell's palsy (idiopathic facial paralysis) (Cochrane Review). In The Cochrane Library Issue 1, 2002. Oxford: Update Software.