WebMD, RxList, MedicineNet and Medscape are the latest to forge ever-closer ties to the pharmaceutical industry after they were purchased by private investment firm KKR (Kohlberg, Kravis, Roberts & Co). The takeover will be finalised by the end of this year.

The sites have always been heavily reliant on advertising income from drug companies—WebMD alone generates around $700m a year—and this has influenced editorial decisions. Medcsape has deleted all negative stories about vaccinations, for example.

But now the pharmaceutical industry has a direct influence over the sites with KKR's $2.8bn purchase. KKR has in its investment portfolio GlaxoSmithKline's older drugs whose patents have expired, Bayer's diabetes equipment division, and 80 per cent of Panasonic Health Care.

Several of their directors and board members also have close ties to the drugs industry, including one executive who is also chairman of Merck.

WebMD's reach in the US is vast, and is one of the country's most influential health websites. It's visited by around 75 million consumers and 650,000 doctors every month.

KKR's Internet Brands division has day-to-day control of the recently-acquired sites. Its CEO, Bob Brisco, said: "WebMD and Medscape are the market leaders in online health with unparalleled reach to consumers and healthcare professionals"—and now they are even better placed to push the pharmaceutical line.