A study to compare the cholesterol lowering potential of two leading statin drugs pravastatin and atorvastatin, have come out with the conclusion that the latter has a superior edge.

The Pfizer-sponsored study presented at American Heart Association meeting in Orlando, Florida, found that atherosclerosis was halted in patients taking high doses of its block-buster atorvastatin brand Lipitor whereas the disease worsened slowly in those who where under Pravachol, a popular pravastatin brand made by Bristol-Myers Squibb.

The new findings have put a question mark on the popular notion that all statins are alike, said Dr Steven Nissen, the cardiologist at the Cleveland Clinic who directed the study of 502 patients.

At the study's start, the middle-aged, mostly male heart disease patients in the study had levels of low-density lipoproteins, or LDL, of 150, on average. LDL carries cholesterol to arteries. Atorvastatin lowered participants' LDL levels to 79, while those taking pravastatin had an average level of 110.

After 18 months, the atorvastatin patients had no change in the plaque in their arteries. But plaque increased by 2.7 per cent in pravastatin patients. The study did not assess patient outcomes like heart attacks and deaths, which would have required 8,000 patients and taken five or more years.

If the two statins had turned out to be about equal, Pfizer might have lost in the multibillion-dollar statin market because pravastatin is nearing the end of its patent life and generic versions should be cheaper.

The study assessed the progression of atherosclerosis using a tiny ultrasound camera that was threaded into coronary arteries, allowing researchers to look directly at the growth of plaque.