When patents on certain products expire, what happens to the price elasticity of demand for that product? For example, if a prescription drug is is under patent the company who produces it has a...

When patents on certain products expire, what happens to the price elasticity of demand for that product? For example, if a prescription drug is is under patent the company who produces it has a monopoly since no other company can copy and produce the drug When the patent expires, other companies and generic manufactures can begin producing the drug In this case, what will happen to the price elasticity of demand for the drug?