When a drug is out for the first time, it’s called a first generation drug. As time goes by, more research is done. The drug is improved or a new, similar drug is made. This is the second generation of that medication.

The process may continue to a third or even, fourth generation. With each new generation, the drug is more effective, more potent, or has fewer side effects. For example, a new group of drugs came out for osteoporosis called bisphosphonates. At first, these had to be given intravenously. The second-generation was made as a pill to be taken by mouth.

There were also major intestinal side effects with this drug. The third-generation is now taken only once a week. It was made especially for patients who couldn’t take other oral bisphosphonates.