A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active chemical substance is the same, the medical profile of generics is believed to be equivalent in performance. A generic drug has the same active pharmaceutical ingredient (API) as the original, but it may differ in some characteristics such as the manufacturing process, formulation, excipients, color, taste, and packaging.
Biopharmaceuticals, such as monoclonal antibodies, differ biologically from small molecule drugs. Biosimilars have active pharmaceutical ingredients that are almost identical to the original product and are typically regulated under an extended set of rules, but they are not the same as generic drugs as the active ingredients are not the same as those of their reference products.
Large pharmaceutical companies often spend millions of dollars protecting their patents from generic competition. Apart from litigation, they may reformulate a drug or license a subsidiary (or another company) to sell generics under the original patent. Generics sold under license from the patent holder are known as authorized generics.
Generic drug companies may also receive the benefit of the previous marketing efforts of the brand-name company, including advertising, presentations by drug representatives, and distribution of free samples. Many drugs introduced by generic manufacturers have already been on the market for a decade or more and may already be well known to patients and providers, although often under their branded name.
In the mid 2010s the generics industry began transitioning to the end of an era of giant patent cliffs in the pharmaceutical industry; patented drugs with sales of around $28 billion were set to come off patent in 2018, but in 2019 only about $10 billion in revenue was set to open for competition, and less the next year. Companies in the industry have responded with consolidation or turning to try to generate new drugs.
Before a company can market a generic drug, it needs to file an Abbreviated New Drug Application (ANDA) with the Food and Drug Administration, seeking to demonstrate therapeutic equivalence to a previously approved "reference-listed drug" and proving that it can manufacture the drug safely and consistently. For an ANDA to be approved, the FDA requires the bioequivalence of a generic drug to be between 80% and 125% of the innovator product. (This range is part of a statistical calculation, and does not mean that generic drugs are allowed to differ from their brand-name counterparts by up to 25 percent.) The FDA evaluated 2,070 studies conducted between 1996 and 2007 that compared the absorption of brand-name and generic drugs into a person's body. The average difference in absorption between the generic and the brand-name drug was 3.5 percent, comparable to the difference between two batches of a brand-name drug. Non-innovator versions of biologic drugs, or biosimilars, require clinical trials for immunogenicity in addition to tests establishing bioequivalency. These products cannot be entirely identical because of batch-to-batch variability and their biological nature, and they are subject to extra rules.
When faced with patent litigation from the drug innovator or patent holder, generic companies will often counter-sue, challenging the validity of the patent. Like any litigation between private parties, the innovator and generic companies may choose to settle the litigation. Some of these settlement agreements have been struck down by courts when they took the form of reverse payment patent settlement agreements, in which the generic company basically accepts a payment to drop the litigation, delaying the introduction of the generic product and frustrating the purpose of the Hatch–Waxman Act.
The Indian government began encouraging more drug manufacturing by Indian companies in the early 1960s, and with the Patents Act in 1970. The Patents Act removed composition patents for foods and drugs, and though it kept process patents, these were shortened to a period of five to seven years. The resulting lack of patent protection created a niche in both the Indian and global markets that Indian companies filled by reverse-engineering new processes for manufacturing low-cost drugs. The code of ethics issued by the Medical Council of India in 2002 calls for physicians to prescribe drugs by their generic names only. India is a leading country in the world's generic drugs market, with Sun Pharmaceuticals being the largest pharmaceutical company in India. Indian generics companies exported US$17.3 billion worth of drugs in the 2017-18 (April-March) year.