One of the ways healthcare companies perform acquisition is via direct mail. It can be a targeted approach to acquire lists and then send patients information. Of course, direct mail can be expensive depending on the piece, and you might expect to get a 1% to 2% response rate on actions like website registrations or calls. Definitely this is an acquisition channel where you can create a basic pro-forma spreadsheet model to gauge potential ROI.
I would recommend Email as an more cost effective alternative for consumer acquisition. These also can be list purchased.
Where do the sources of the lists come from? They are opted in at various sources by the consumers who note that they have a particular condition. The sources of a pharmaceutical direct mail piece to patients is illuminating; see this blog entry and article.
I recommend a test and learn approach when it comes to pharma lists for direct mail or email. Rent a random fraction of the list and see the response rate. Or better yet, use a quantitiy you can afford. Also, consult an agency you trust to find the right list suppliers.