A fixed-dose combination or FDC drug contains two or more active ingredients in a fixed dosage ratio. For example, one of the FDCs in the banned list is "naproxen plus paracetamol", meaning it's not the single drug but a combination of the two that has been ascertained as unnecessary for consumption.

The government has added restrictions to dosage and use of six more FDCs -- not among the 328 banned ones -- over their ingredients having no therapeutic value and posing a risk to consumers.

The health ministry took the decision after the country's top drug advisory body, the Drug Technical Advisory Board or DTAB, in a report said taking the 328 FDCs would be a health risk. India has some 2,000 FDCs as against a little over 500 in the US.

"The Delhi High Court stayed this (FDCs ban) on technical grounds, but it is a good move for public health. Individual drugs are approved by the centre, but some manufacturers make combinations of two drugs and get state licences," Dr KK Agarwal, former president of Indian Medical Association, told NDTV.

Mixing two drugs create a new medicine, Dr Agarwal said. If it's a new medicine, pharma companies should approach the Drugs Controller General of India and apply for a fresh licence, conduct trials, prove safety and only then go to the market, Dr Agarwal said.

Most firms have already discontinued their FDCs or have little stock left with them, Dilip Shah of industry body Indian Pharmaceutical Alliance told NDTV. It will take two days for the banned FDCs to disappear from shops from the time the manufacturers tell their distributors and wholesellers to withdraw the medicines.

President of the Indian Drug Manufacturers' Association, Deepnath Roychowdhury, said the order would have an impact on a market worth an Rs 16 billion a year for such drugs, which are produced by both small and large pharmaceutical companies. He said the verdict would be respected, news agency Reuters reported.

In March 2010, the government restricted sales of 344 FDCs, a move that was challenged by pharma firms in court. The Supreme Court last December told the DTAB to ascertain whether FDCs should be banned from the market.

In 2016, several top pharmaceutical firms including Pfizer Ltd and Glenmark Pharmaceuticals Ltd had gone to the Delhi High Court to challenge the centre's move to ban a separate list of 344 FDCs, including brands like Corex cough syrup, Vicks Action 500 and D'Cold. The court later stayed the government's ban.