US regulators have given Merck & Co and Schering-Plough some good news at last over Vytorin, saying that the cholesterol drug should still be prescribed.

The US Food and Drug Administration said that it has completed its review of the controversial ENHANCE study comparing Vytorin (ezetimibe/simvastatin) with Zocor (simvastatin) and has concluded that patients on the combination drug should continue treatment. The agency noted that preliminary results from the study showed that there was no significant difference in the changes in carotid (neck) artery thickness among patients in either treatment group, and the FDA's review of the final clinical trial report of ENHANCE confirmed this finding.

However, the agency also noted that Vytorin significantly lowered levels of LDL (bad) cholesterol. The latter was reduced by 56% for those patients given Vytorin, versus 39% for those on Zocor. "The results from ENHANCE do not change FDA's position on the benefits of lowering LDL cholesterol," the FDA said.

The FDA went on to note that the ongoing IMPROVE-IT trial, which involves 18,000 patients and is scheduled to be completed in 2012, is looking at whether treatment with Vytorin reduces the risk for cardiovascular events compared with Zocor alone. However until those results are published and "patients should not stop taking Vytorin or other cholesterol-lowering medications," the agency advised.

The FDA’s review represents good news for Merck and S-P which have seen sales of Vytorin slump after ENHANCE raised questions about whether the drug worked better than the much-cheaper Zocor on its own.