Nearly two-thirds of multi-drug antibiotic cocktails sold in India between 2007 and 2012 were unapproved, said researchers on Monday, warning such "illegal" compounds were fuelling the spread of drug-resistant diseases.
In total, 118 different types of "fixed-dose combination" antibiotics -- formulations combining two or more drugs in a single pill -- were sold in India in the five years under review, a team reported in the British Journal of Clinical Pharmacology.
Of these, "64% were not approved by the national drugs regulator, the Central Drugs Standard Control Organisation", they said.
The sale of unapproved drugs is illegal in India.
The 118 formulations were sold as 3,307 different brand-named products, produced by 476 pharmaceutical companies -- including a dozen multinationals, said the team.
There were also 86 single-drug formulations, of which 93% had regulatory approval.
"Selling unapproved, unscrutinised antibiotics undermines measures in India to control antimicrobial resistance," said the study's lead author Patricia McGettigan of the Queen Mary University in London.
"Multinational companies should explain the sale of products in India that did not have the approval of their own national regulators and, in many cases, did not even have the approval of the Indian regulator," she said in a statement.
India already has one of the highest rates of drug resistance in the world, said the team, coupled with one of the highest antibiotic consumption rates.
The UN warns that the emergence of drug-resistant germs is a "global health emergency" threatening progress made by modern medicine, and risking a future in which people die of ailments that are easily curable today.
A report commissioned by the British government warned in 2014 that antibiotics-resistant infections could kill 10 million people per year globally by 2050, making it the leading cause of death over heart disease and cancer.
Bacteria acquire drug resistance partly through exposure to antibiotics.
Instead of killing the germs, the wrong type of antibiotic or the wrong dose can stimulate the bugs to fight back -- either by spontaneous DNA mutations that confer immunity, or by transferring resistant genes between themselves.
This can also happen when humans are exposed to antibiotics in animals they consume, or in the water or soil they come into contact with.