Friday, Federal Drug Administration officials announced the launch of an investigation on Amgen and Johnson & Johnson’s experimental drugs for anemia. The latter company revealed this month that the results of a German trial showed a higher death rate in stroke patients who were given the drug than in the placebo-treated group. The research was aimed at finding whether the medication could benefit a stroke patient’s brain functions, although the FDA has only approved of Eprex’s use in raising red blood cell levels in people who suffered from anemia.

A number of 522 people, most of whom were not anemic (according to the FDA), were given relatively high doses of the drug or a placebo over a period of three days. Bleeding in the brain accounted for 4% of the deaths in the Eprex-group, as opposed to 1% in those who had taken a placebo.

Three months after the study began, sixteen percent of those who had received Eprex died (most of which within a week after the study ended), while the percentage in the other group was only nine percent.

Anemia is the most common blood disorder worldwide, causing fatigue and sometimes concentration problems. Since it leads to lack of oxygen in the organs, its further clinical consequences spread over a large array of medical conditions.

In a statement posted online, federal health regulators said they would be looking into the risks and benefits of the drug’s experimental use.

Amgen sells generically known epoetin alfa Exprex under the Epogen name, while Johnson & Johnson comercializes the drug under the name of Procrit.

The FDA informed that they expected to receive further data within the following weeks and that it would make the resultsof their investigation public once their review was finished.