Fake or substandard drugs for tuberculosis are in full circulation in Africa, India and other developing countries, where it is prompting the rise of treatment-resistant strains of tuberculosis, according to a survey published on Tuesday.
Investigators in the United States asked local people in 19 cities in 17 countries to purchase isoniazid and rifampicin, the frontline antibiotics for tuberculosis (TB), from a private-sector pharmacy.
Out of 713 samples, 9.1 percent failed these basic quality-control tests, according to the inquiry, published in the International Journal of Tuberculosis and Lung Disease.
Around half of the failed samples had zero active ingredients, "making them likely to contribute to drug resistance", it said.
Dud drugs were manufactured by legitimate companies and criminal fraudsters, the report said.
The drugs were purchased at pharmacies in Luanda, Sao Paulo, Beijing, Lubumbashi, Cairo, Addis Ababa, Accra, Chennai, Delhi and Kolkata, Nairobi, Lagos, Moscow, Kigali, Dar-es-Salaam, Bangkok, Istanbul, Kampala, and Lusaka.
The failure rate was 16.6 percent in Africa, 10.1 percent in India and 3.9 percent in Brazil, China, Thailand, Turkey and Russia.
Nearly nine million people around the world have TB, one of the world's deadliest diseases, including more than 400,000 with a multidrug-resistant form of the disease, according to estimates for 2011 compiled by the World Health Organisation (WHO).
Drugs that do not work is a contributing factor to resistance to TB drugs, along with treatment that fails to kill the bacteria.
TB is one of the world's deadliest diseases. It is spread from person to person through the air and usually affects the lung.