NEW DELHI: After last week's ban on 344 medicines, as many as 500 more drugs - including antibiotics and anti-diabetes drugs - may be outlawed for being "irrational", unsafe and ineffective, official sources have said.Last week, as first reported by TOI, the ministry banned 344 fixed-dose combination (FDC) drugs including commonly-used cough syrups like Phensedyl, Corex and Benadryl.Now, a senior official says, the ministry is evaluating a list of over 6,000 products, of which at least 1,000 more FDCs are under "severe scrutiny". As many as 500 of those drugs will likely be banned in six months."There is primary evidence in around 1,000 cases, which shows these are irrational FDCs. However, in some cases, the data is incomplete so we have asked for further studies. In around 500 cases, we are at the last leg and waiting for some documents," an official told TOI. The health ministry believes that "irrational" FDCs are causing anti-microbial resistance and in some cases their toxicity is so high they can even lead to organ-failure. There are also concerns that these FDCs being available over-the-counter, without doctors' prescriptions, is leading to their misuse."Our objective is to ensure only safe products are available in the market. We have reviewed products for several times and there is evidence from research papers and studies to show these medicines are irrational combinations," the official said.In the meanwhile, the Delhi high court on Monday granted pharmaceutical firm Pfizer a stay order, pending a further hearing, on the ban on its popular cough syrup Corex.Some drug makers, including Pfizer, have argued that some of the banned drugs have been available in India for around 30 years and so must be safe. Health ministry officials have countered that a long market life isn't enough to prove safety."Just because adverse events have not come to notice or have not been reported so far does not mean we ignore scientific evidence showing discrepancies," the official said.Officials and health experts say that adverse effects of these drugs are not often reported because patients don't come back to doctors unless these drugs are used repeatedly and lead to severe problems. Also, because of a weak vigilance mechanism, the adverse impact of such drugs is often not reported.While industry estimates have pegged a revenue loss of at least Rs 3,800 crores for the 344 banned FDCs' makers, pharmaceutical firms may have to bear a much wider loss if 500 more drugs are banned.Some industry executives say the cumulative loss could be as much as Rs 10,000 crores.The total local pharmaceutical retail market is pegged at over Rs 1 lakh crores annually.