Most over-the-counter bottles are made of high-density polyethylene (that's No. 2 plastic), though some may be made of polyethylene terephalate (No. 1). Both types are widely recyclable, but many local curbside programs won't take them, because they're small and can jam up equipment. Meanwhile, amber prescription bottles are usually polypropylene (No. 5), which is rarely accepted by recyclers. The design company Preserve collects No. 5 plastics at many Whole Foods, though, and you can also mail your polypropylene empties directly to the company. Some shelters, clinics, and veterinarians' offices also collect prescription vials and reuse them, so if you've got a whole bunch of them on your hands, it might be worth looking for such a facility in your area. The Lantern likes to use hers as coin containers or carrying cases for earrings and safety pins while she travels.
Meanwhile, if you want to reduce the footprint of your personal pharmaceutical habit, you should also spare a thought at the beginning of the process. Buying in bulk usually makes a lot of environmental sense, but those benefits are undercut if you have to throw away an unused product because it's gone bad. If you know you're not going to consume 500 Advil capsules before the expiration date, go for the smaller bottle.
Is there an environmental quandary that's been keeping you up at night? Send it to firstname.lastname@example.org, and check this space every Tuesday.