Web sites for Merck’s type 2 diabetes drug Januvia, Merck’s asthma and allergy treatment Singulair and GlaxoSmithKline’s asthma medication Advair were the top three online product destinations respectively among US primary care doctors in 2007, a new study shows.

Market research firm Manhattan Research, which coordinated the study, said the purpose of the analysis was to better determine the leading online physician destinations based on the satisfaction and number of physician visitors.

“The latest research reveals physician site traffic is spread among product sites of new and early launch stage treatments, those with clinical news coverage, and consistent with years past, products with a significant consumer advertising component,” Manhattan Research president Mark Bard said in a statement.

Rounding out the top 10 pharmaceutical product Web sites among physicians in 2007, ranked by number of US primary care physician visitors, were:

4. Pfizer’s smoking-cessation aid Chantix

5. Shire’s ADHD treatment Adderall XR 

6. Lilly’s type 2 diabetes treatment Byetta

7. Merck’s HPV vaccine Gardasil

8. Merck and Schering-Plough’s joint-venture cholesterol-lowerer Vytorin

9. GlaxoSmithKline’s diabetes treatment Avandia

10. McNeill’s ADHD treatment Concerta

“We have seen these product sites evolve into brand gateways with visitation from physicians, healthcare professionals, and consumers and with the majority of the top 10 product sites changing from year-to-year, there is clearly a need among physicians for the most up-to-date product information,” Bard added.