NEW DELHI, Oct. 16 -- India plans to overhaul its drug patent rules to stop pharmaceutical companies from evergreening patents through minor modifications and artificially extend market monopolies.

New draft guidelines issued by the Office of the Controller General of Patents, Designs and Trade Marks under the ministry of commerce and industry propose to set stricter evidentiary benchmarks to verify inventions and prevent patent extensions that delay generic versions.

The planned framework is significant for India's $60 billion pharmaceutical industry, which accounts for a fifth of the world's generic medicine supplies and ranks third globally by volume. Once a drug patent expires, the original manufacturer no longer holds a monopoly on...