Essential drugs for rare diseases

Pharmaceutical companies or institutes introduce several drugs in the market after authorization by regulatory agencies of the respective country. The drug which comes first in the market is called as prototype drug and other related drugs with similar mechanism of action are called as congeners. Each pharmaceutical company obtains a patent on that congener and can market it exclusively till the end of patent life of that drug. Once the patent life is over, other pharmaceutical companies can market the drug with a generic name or their own trade name. Every new drug is given a new international nonproprietary name (INN) by an international body. The INN is also called as generic name of the drug, while every company can give a trade name for their own drug and is called as Brand name. As a result of market competition and a desire of promoting their own brand names, there are few thousand drugs with their own INNs and brand names in the global market.