The company has "emerged successful in revoking composition patents of Allergan," it said in a statement.
Ajanta had challenged the two patents granted to Allergan in 2011 on grounds of "obviousness, not an invention, not patentable, insufficiency and non-disclosure under section 8 of the Patent Act," the drug firm said.
The Kolkata-based Patent and Design Office had granted two patents to Allergan for the composition covering Bimatoprost and Timolol (sold under the Ganfort brand), and Timolol Brimonidine and Timolol (sold as Combigan), which are used for eye-related treatments.
"Ajanta has already been successfully selling Bimat T and Bidin LS (the generic versions of the drugs) in the Indian market and will continue to sell backed by this favourable verdict," the drug company said.
In its ruling revoking the patents, the Chennai-based Intellectual Properties Appellate Board said: "We have found the claimed invention as obvious."
Earlier this week, the government had "treated as withdrawn" patent applications by Swiss pharma major Roche Holding for offshoot medicines of its breast cancer drug 'Herceptin' because the company did not comply with local norms.