OBJECTIVEThis study estimated the health economic impact of olopatadine (Opatanol) compared to branded cromoglycate (Opticrom) and generic sodium cromoglycate in the treatment of seasonal allergic conjunctivitis (SAC) in the UK.DESIGN AND SETTINGThis was a modelling study performed from the perspective of the UK's National Health Service (NHS).METHODSA decision model was constructed depicting the management of SAC sufferers who are 4 years of age or above over a typical allergy season of 4 months and considers the decision by a GP to initially treat a patient with olopatadine, branded or generic cromoglycate. The analysis assumed both drugs to be equally effective. Consequently, a cost-minimisation analysis was performed to identify the least costly alternative.MAIN OUTCOME MEASURES AND RESULTSStarting treatment with olopatadine is expected to lead to a healthcare cost of 92 pounds sterling (95% CI: 46 pounds sterling; 150 pounds sterling) over 4 months compared to 109 pounds sterling (95% CI: 65 pounds sterling; 166 pounds sterling) with branded cromoglycate and 95 pounds sterling (95% CI: 51 pounds sterling; 152 pounds sterling) with generic cromoglycate, resulting in a 16% and 3% reduction in healthcare costs respectively over 4 months of treatment. This cost-difference is primarily due to fewer GP visits among olopatadine-treated patients.CONCLUSIONUse of olopatadine instead of branded or generic cromoglycate affords an economic benefit to the NHS. Hence, within the limitations of the model, olopatadine is the preferred first-line treatment for use in SAC sufferers, since it is expected to lead to fewer GP visits, thereby releasing healthcare resources for alternative use.