New Delhi: Indian authorities are closely monitoring the sale of heartburn drug Ranitidine after the US drug regulator said it had found a cancer-causing impurity called N-nitrosodimethylanine (NDMA) in some products containing Ranitidine.Ranitidine is a commonly prescribed medicine for countering acidity and is on the World Health Organisation’s ‘Model List of Essential Medicines’. In India, a host of companies including GalxoSmithKline, JB Chemicals, Cadila Pharma, Zydus Cadila, Dr Reddy’s, Sun Pharmaceuticals sell over 180 versions of the drug. The market size for Ranitidine brand in India is Rs 688.6 crore, as per data shared by AIOCD PharmaTrac.To ensure patient safety, the Drug Controller General of India (DCGI) on Tuesday directed state drug regulators to ask pharmaceutical companies to check their products for the carcinogen . It also asked them to ensure that the drug is sold only under prescription.“The drug Ranitidine is approved for multiple indications in the country and is available in various formulations including tablets, injections, etc. It is a prescription drug included in Schedule H and, therefore, it should be sold by retail only under prescription of a registered medical practitioner,” the DCGI’s letter said. ET has seen a copy of the letter.Last week the US and European Union regulators said they were investigating the discovery of NDMA in branded and generic Zantac. “Subject experts have also been reviewing the situation and an advisory may follow in the days to come, but as of now there is nothing to panic,” said a senior official in the drug regulatory authority, requesting not to be named.Experts vouch for the benefits of the medicine. "Ranitidine is one of the oldest drugs to be used in acidity and upper intestinal ulcers, and has been considered to be safer than similar other drugs like proton pump blockers (eg. Pantoprazole), said Anoop Misra. Chairman, Fortis-C-DOC Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology.“We are using it frequently, especially in patients with renal dysfunction.”According to a GSK spokesperson, the company has been contacted by India’s drug regulatory authorities regarding the detection of NDMA in Ranitidine products and the queries have been responded to. “GSK is continuing investigations into the potential source of the NDMA. These investigations include continued engagement with GSK’s API suppliers, including Dr. Reddy’s and Saraca Laboratories Limited. GSK has engaged external laboratories to conduct tests on the API and on the finished product batches of Zantac IV (injection). Initial results are expected by the end of September 2019. The testing is being extended to include batches of tablets and potentially other dose forms. Market-specific test results will be available later,” the spokesperson said.A spokesperson for Sanofi said the company does not sell the product in India. “Ranitidine prescription products have been authorised on the market for over 35 years and in a number of markets an OTC version of ranitidine has been available to consumers for over two decades.The range of products meet all specified quality and safety requirements for use,” the person said.