One person was in a coma and five others hospitalised after having negative reactions to a medication they were taking as part of a medical trial in north-western France, the country's health ministry said today.

The drug was being tested on healthy volunteers by French company Biotrial in Rennes as part of an early phase trial for an unnamed client.

Neither the ministry nor Biotrial have indicated what the drug was, other than to say that it was an oral medication.

France's health ministry said that the person in the coma was medically brain dead.

Biotrial said in a statement that "serious adverse effects" had occurred during the study but that it had complied with all safety regulations.

Drug manufacturers often contract independent clinical trial companies to conduct tests.

The company, based in Rennes, also has offices in London and in New Jersey, US. Volunteers who agree to participate in trials in France can earn between 100 and 4,500 euros (US$110 and US$4,933), Biotrial said.

French Health Minister Marisol Touraine called the test a "serious accident" and was traveling to Rennes this afternoon (French time).

Experimental medications go through multiple phases of testing before they are approved for commercial use. In the first phase, researchers test a drug on a small group of volunteers to check for side effects before administering the drug in phase two to a larger group to evaluate effectiveness.

A medication usually goes through one more pre- and one post-market testing phase to gather more information about effects.

It is uncommon for clinical tests to risk to trial participants.

The last major drug trial disaster in the pharmaceutical industry was in 2006, when German company TeGenero had a drug tested against multiple sclerosis in Britain.

Within moments of having the drug administered, six volunteers in the 2006 study began showing severe reactions, and a few hours later doctors began noting organ failure.

One participant remained in a coma for three weeks. TeGenero declared bankruptcy a few months later, and dosages allowances for testing were lowered.

- dpa