The combination includes Intron-A, which Schering-Plough already sells alone to treat hepatitis, and ICN's drug ribavirin, or Rebetol.
Studies have shown the two drugs together provide a significant benefit to patients. Schering will sell the combination in a single package containing the Rebetol pills and injections of Intron-A, under the name Rebetron.
"This combination should be seriously considered by practitioners in this field," said Judith Feinberg, an associate professor in the division of infectious diseases at the University of Cincinnati Medical Center and a member of the FDA advisory panel that recommended approval of the drug combination last month.
Shares of Madison, N.J.-based Schering-Plough rose $1.88 to $84.88 on Wednesday, and shares of Costa Mesa-based ICN were up 81 cents at $42.50. Both trade on the New York Stock Exchange.
The approval was expected because the FDA advisory panel backed the combination therapy after hearing that patients who take it increase tenfold their chances of beating back the virus. Schering is readying an application for use of the drug as a first-line treatment in hepatitis C patients.
The combination Schering-ICN therapy has drawbacks. Intron-A is already a hard drug to take, with injections often causing flu-like symptoms. The combination adds the side effects of a regimen of pills on top of that.
Pregnant women shouldn't take the drug combination, the FDA said.
Experts estimate that almost 4 million Americans are infected with hepatitis C, a virus most often transmitted through contaminated needles, or a tainted blood transfusion before screening tests were available. ICN will receive royalties on the regimen to be marketed by Schering-Plough. ICN currently sells its drug in another form, under the brand name Virazole, for treating respiratory infections.