MONDAY, Sept. 18 (HealthDay News) -- A new molecular drug designed to prevent fungal infections in post-surgical patients and others with weaker immune systems has been approved by the U.S. Food and Drug Administration.

Schering Corp.'s Noxafil (posaconazole) contains a substance that has never before been approved in the United States, the FDA said in a statement. The drug was approved to prevent infections caused by certain molds and yeast-like fungi called Aspergillus and Candida.

While people with healthy immune systems are normally unaffected by these fungi, they tend to cause invasive infections in people who have had bone-marrow transplants and people with low white blood cell counts, the agency said.

Noxafil's safety and effectiveness were evaluated in clinical trials involving 1,844 people between ages 13 and 82. Common side effects included nausea, vomiting, diarrhea, rash, a drop in blood potassium levels, and in rare cases, problems with heart or liver function.

The drug should be taken with a full meal to allow for adequate absorption into the body, the FDA said.