Spamdexing is a method used to inflate the search engine rankings of a particular page, generally for malicious or unethical purposes. Attackers modify pages on legitimate sites to contain keyword-rich links to promote the sites of their choosing. Because the search engine will rank the links based on the popularity of the compromised site, spamdexing can often result in malicious links appearing at the top of search engine results pages (SERPs).
Spamdexers tend to favor .edu sites for their spamdexing campaigns, and it seems that many .edu site admins don't seem to care. When RSnake of ha.ckers.org tried to reach out to some of those admins and notify them of the problem, they either didn't respond or accused him of ambulance chasing. His blog post, ".EDU Hacks and Ambulance Chasing", provides some example searches that reveal just how widespread the problem is.
Before you proceed to try any of those searches, it's probably worth noting here that the majority of online pharmaceuticals are likely to be counterfeit pills that at best do nothing and at worst can cause real physical harm.