The thing that really gives a domain value is the available market for the keywords. For example, a domain like Texas.com would have a market of all of Texas which is millions and millions of people. So since the potential market for this domain is so large, the value of the domain would be large.
One you define the base potential market other things go into the value such as length, how cute and catchy is it, and so on and so on. But for the most part with your domain I'm sort of stuck on potential market.
On one hand the pharmaceutical market is rather large and pretty much covers most adults as we all have needs for meds at one time or another and who hasn't been concerned with drug interactions. Especially considering the fact that as of 2010 there will be more people retired than of working age - that means we will have a massive market of old folks who need meds more than the younger people and that opens up and even bigger market for your domain.
However all of that said, I question the defined meaning of the phrase Dirty Drugs. Which got me digging and it seems that subject is rather a hot topic right now for cancer research and that's good for the base value of your domain.
But like I suspected, it also has a lot to do with naughty drugs and less with the pharmaceutical market and as such it makes the value of the domain probably in the high $xx but with some development, pushing the drug interaction aspects, you could really really really really really really really increase the value of this domain.