He expects the group's revenue growth to drop back to 10 percent in 1996 when the stream of patent expirations dwindles.

That reset the clock for Claritin's patent expiration to the summer of 2000.

In fact, we could go through a period where a number of these companies that are facing patent expirations will perform better than expected.

The abrupt drop in sales expected after the date of patent expiration can be estimated with the following formula:

While they struggle with new technologies, the companies are facing a steady stream of patent expirations on their most profitable drugs.

If granted, these patents 'reset the clock' on patent expiration.

First, the rate of patent expiration is increasing.

New-product launches and patent expirations are the key growth variables right now.

Secondly, though, many of the 1990's-era blockbusters were facing patent expiration or successful challenges.

The reason for Merck's current earnings problems "really is the patent expirations," he said.