Two blockbuster drugs from two of world's top drug makers, Pfizer and Merck have lost their patent protection in June marking the beginning of a massive price drop of these drugs in the world markets. Patent of Zocor, the anti cholesterol drug of Merck already expired on June 23. With this Merck loses its monopoly over its cholesterol molecule, simvastatin, with annual worldwide sales of $4.4 billion. Pfizer's antidepressant drug, Zoloft, with $3.3 billion sales, is another drug which lost the patent protection on June 30. When a drug loses its patent, the price of the drug and its sales tend to drop by 80 per cent within an year, as competition opens up for a host of generic drug makers. It is possible, therefore, that both Merck and Pfizer may face substantial dip in their sales volumes and margins in the coming months. They will, however, continue to produce their branded drugs as millions of dollars in annual sales can still be realized from patients who prefer the brands they used to buy. A large number of patients with strong product loyalty may not immediately switch over to generic versions but could stick to Zocor and Zoloft. Both Merck and Pfizer may also attempt to launch spin-offs of their brands adding suffixes or prefixes with tweaked indications. Introduction of extended release versions of the patent expired drugs is another marketing gimmick the drug makers indulge in a bid to retain sales. Two immediate beneficiaries of patent expiry of Zocor, the second largest selling cholesterol drug, are Teva and Ranbaxy. Both of them have obtained 180 days exclusivity for marketing generic simvastatin of various strengths in the US market starting from June 23. That assures a major gain for both the companies during the six months period. Dr. Reddy's Labs also stands to gain as it is likely to be the supplier of authorized generics to Merck. A dozen other drug makers who have obtained clearance from US FDA for marketing generic versions of the drug, will enter the market only after the six months. Only then a real market crash of simvastatin, and probably other statin prices, will take place in the world markets. Simvastatin is being marketed under different brands in India at very high prices by various leading Indian companies as it is outside price control. And Ranbaxy's Simvotin is the widely prescribed and most expensive brand in the country. A possible outcome of Zocor's patent expiry is that it could threaten the sales of Pfizer's Lipitor, world's top selling drug with $ 12.2 billion in sales. A good number of physicians in the US and Europe are encouraging their patients to use Zocor instead of Lipitor. Pfizer's Lipitor, another cholesterol drug, atorvastatin is under patent and was introduced by Pfizer in 1997. The drug is most widely prescribed cholesterol lowering therapy in the world and is approved in more than 70 countries. The Lipitor patent is challenged in different countries by various generic companies including Ranbaxy. Courts in many countries have so far upheld Pfizer's patent claim for the drug. But, once any court rules against Pfizer that will be the end of Lipitor monopoly too.