rickets is a nutritional disorder that can develop if you do not get enough vitamin d calcium or phosphate rickets leads to poor functioning of a bone s growth plate growing edge softened and weakened bones stunted growth and in severe cases skeletal deformities
Hence, a 20-year period of the patent usually gives manufacturers a chance to recoup the cost of developing a new drug. When a drug patent expires, any pharmaceutical company can manufacture and sell the drug. A drug, which is produced and distributed without patent protection is called a generic drug.
Under the FDA rule, drug companies must test their drugs to be sure they are stable for as long a period as the company wants to claim the expiration date is. So if a drug is made in May 2000 and the company has conducted testing that the drug will remain safe and potent for two years, the expiration date is May 2002.