Well, this is a question that (I must admit) had not crossed my mind. Courtesy of Slate, though, we can now ask how we can make pharmaceuticals more environmentally friendly. No, not the manufacturing processes: this article's worried about the drugs that are excreted into the water supply.
It's worth keeping an eye on this issue, but I haven't been able, so far, to get very worked up about it. It's true that there have been many studies that show detectable amounts of prescription drugs in the waste water stream. The possible environmental effects mentioned in the article, though, are seen at much higher concentrations. I think that much of the attention given to this issue comes from the power of modern analytical techniques -if you look for things at parts-per-billion level (or below), you'll find them. Of course, you'll also find a huge number of naturally occurring substances that are also physiologically active: can the synthetic estrogen ligands out there really compete against the huge number of phytoestrogens? I have to wonder. To me, the sanest paragraph of the article is this one:
Developing "benign-by-design" drugs poses a series of vexing challenges. In general, the qualities that make drugs effective and stable—bioactivity and resistance to degradation—are the same ones that cause them to persist disturbingly after they've done their job. And presumably even hard-core eco-martyrs (the ones who keep the thermostat at 60 all winter and renounce air travel) would hesitate to sacrifice medical efficacy for the sake of aquatic wildlife. What's more, the molecular structures of pharmaceuticals are, in the words of Carnegie Mellon chemist Terry Collins, "exquisitely specific." Typically, you can't just tack on a feature like greenness to a drug without affecting its entire design, including important medical properties.
And even that one has its problems. That "persist disturbingly" phrase makes it sound like pharmaceuticals are like little polyethylene bags fluttering around the landscape and never wearing down. But it's worth remembering that most drugs taken by humans are metabolized on their way out of the body, and most of these metabolites don't maintain the activity of the parent compound. Other organisms have similar metabolic powers - as living creatures, we've evolved a pretty robust ability to deal with constant low levels of unknown chemicals. (Here's a good chance to point out this article by Bruce Ames and Lois Swirsky Gold on that topic as it relates to cancer; many of the same points apply here).
No one can guarantee, though, that pharmaceutical residue will always be benign. As I say, it's worth keeping an eye on the possibility. But it will indeed be hard to do something about it, for just the reasons quoted above. As it is, getting a drug molecule that hits its target, does something useful when that happens, doesn't hit a lot of other things, works in enough patients to be marketable, has blood levels sufficient for a convenient dose, doesn't cause toxic effects on the side, and can be manufactured reproducibly in bulk and formulated into a stable pill. . .well, that's enough of a challenge right there. We don't actually seem to be able to do that well enough as it stands. Making the molecules completely eco-friendly at the same time. . .