Finally, because all the patents are held in one place, it is much easier to create combination pills.

Others have hastened to patent the chemicals involved and are planning to incorporate them into new combination pills.

The most encouraging finding was that estrogen alone, unlike the combination pills, did not increase the risk of breast cancer.

Patients on the combination pill take one in the morning and one at night.

These combination pills work on most of the symptoms of allergies.

Plan B contains a higher dose of the same synthetic hormones found in the combination pill.

Most combination pills come in 21- or 28-day packs.

But Pfizer will need years to make the combination pill a standard treatment for cholesterol, analysts say.

The company is planning a clinical trial to test the combination pill against Combivir.

By planning to offer only a combination pill, Pfizer is taking the marketing strategy one step further, analysts said.