Irvine-based drug maker Allergan Inc.’s shares fell sharply today after analysts downgraded the company over possible generic competition for its Restasis dry-eye treatment.

Allergan shares were down 10% to a market value of about $25 billion in midday New York trading after analysts from Piper Jaffray, Leerink Swann LLC and Deutsche Bank wrote that a Food and Drug Administration opinion could clear the way for a generic competitor for Restasis.