Merck's new diabetes drug Januvia, which only won FDA approval in mid-October, is off to a strong start in the United States, according to compiled by market research company ImpactRx Inc.

The company, which combines free samples dispensed by doctors with new prescriptions written, said primary care physicians in the week ending Nov. 17th chose Januvia for 14 percent of their patients with type 2 diabetes.

While this trailed the 26 percent of patients who were given the standard diabetes option Metforin and the 23 percent given the diabetes drug Actos, Januvia's share equaled that of Avandia -- a member of the same class of medicines as Actos -- and exceeded the 9 percent registered for Byetta.

Januvia, which belongs to a new class of medicines called DPP-4 inhibitors that work by enhancing the body's own ability to lower blood sugar, was even more frequently the choice of endocrinologists, according to ImpactRX.

While Byetta was the most frequent choice of endocrinologists with 22 percent, Januvia accounted for 20 percent of new prescriptions plus new samples, compared with 19 percent for Avandia, 16 percent for metformin, and 10 percent for Actos.

"In situations where physicians are making a brand choice, it's clear that Januvia is off to a strong start and Merck looks to be putting the promotional muscle behind it to make that happen," said Patrick Angelastro, senior vice president of strategic development for ImpactRx.