Objectives. Bell's palsy (BP), which causes facial paralysis, affects 11-40 people per 100 000 per annum in the UK. Its cause is unknown but as many as 30% of patients have continuing facial disfigurement, psychological difficulties and occasionally facial pain. We present an randomised controlled trial (RCT)-based economic evaluation of the early administration of steroids (prednisolone) and/or antivirals (acyclovir) compared to placebo, for treatment of BP. Methods. The RCT was not powered to

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... detect differences in the cost-effectiveness; therefore, we adopted a decision analytic model approach as a way of gaining precision in our costeffectiveness comparisons [e.g. prednisolone only (PO) versus acyclovir only versus prednisolone and acyclovir versus placebo, prednisolone versus no prednisolone (NP) and acyclovir versus no acyclovir]. We assumed that trial interventions affect the probability of being cured/ not cured but their consequences are independent of the initial therapy. We used the percentage of individuals with a complete recovery (based on House-Brackmann grade = 1) at 9 months and Quality Adjusted Life Years (e.g. derived on responses to the Health Utilities Index III) as measures of effectiveness. Other parameter estimates were obtained from trial data. Results. PO dominated-i.e. was less costly and more effective-all other therapy strategies in the four arms model [77% probability of cost-effective (CE)]. Moreover, Prednisolone dominated NP (77% probability of being CE at £30 000 threshold) while no acyclovir dominated aciclovir (85% chance of CE), in the two arms models, respectively. Conclusions. Treatment of BP with prednisolone is likely to be considered CE while treatment with acyclovir is highly unlikely to be considered CE. Further data on costs and utilities would be useful to confirm findings.