An embarrassed Astra-Zeneca just lost a very public “smack down” with rival drug maker Pfizer. Both consumers and the pharmaceutical industry were anxiously awaiting the results of the pharmaceutical equivalent of the “fight of the century” – a toe-to-toe match between blockbuster cholesterol reducing drugs Crestor and Lipitor.

But in the just-announced trial results, Crestor failed to clearly best Lipitor at clearing clogged arteries. Although it did demonstrate what Astra-Zeneca called a “numerically greater” effect, it did not achieve the statistical significance that would have provided the cholesterol drug with an obvious victory.

The researchers measured the amount of plaque in two different ways, by total volume and percentage volume. Crestor reduced the total volume of fatty deposits in the artery more than Lipitor, but on a percentage basis – the study’s chief measure of effectiveness – the result wasn’t a knock-out.

Pharmaceutical giant AstraZeneca was so convinced of its cholesterol drug’s superiority that it sponsored the clinical trial, called the Saturn study. Crestor is generally considered the more effective of the cholesterol medications, and past trials suggested that high doses of Crestor could beat high doses of Lipitor at reducing levels of “bad” LDL cholesterol and increasing levels of “good” HDL cholesterol.

Shares in AstraZeneca fell upon news of its discomforting failure to best its rival. The timing of this clinical study was critical, as Lipitor is about to go off-patent at the end of 2011, allowing other drug companies to market it as cheaper generic atorvastin. Had Crestor proved the victor in the head-to-head battle, its loss of market share to the cheaper generic Lipitor would have been greatly reduced.

But the calculated risk failed to pay off, and there is now little incentive for doctors to prescribe, and patients to pay extra money for, the pricy patented cholesterol drug. The results threaten to topple Crestor’s champion status as Astra-Zeneca’s biggest-selling drug, with US sales of $2.64 billion in 2010.

Rival Lipitor was the second top-selling prescription drug in the US in 2010 (behind Nexium and followed by Plavix). Crestor lagged behind in ninth place. Lipitor is a top-seller across the world. Generic Lipitor has been available in Canada since early 2011, making cheap Lipitor from Canada available to Americans through online Canadian pharmacies.

Both Crestor and Lipitor are statins. A statin is a cholesterol-lowering drug that reduces LDL cholesterol by reducing the liver’s ability to make cholesterol, and by helping the body to reabsorb cholesterol plaque that has accumulated on the artery walls. High cholesterol is a major risk factor for heart attack and stroke.