I found this online. It doesn't specifically say pharmaceuticals but it's helpful.
Types of Water Filters
The simplest, and often least expensive, water purifiers are those that use a
carbon-activated filter. These include pitchers with built-in filters as well as those that attach directly to faucets or to plumbing below the sink. Those using granulated charcoal may be slightly less effective than solid block charcoal filters. Carbon filters will generally remove chlorine, coarse sediment, lead and some organic chemicals. The simplest types won't filter out pathogens, some pesticides and some heavy metals, but those with a combination of filters are more likely to.
The most comprehensive, and most expensive, water purifiers are
reverse-osmosis systems. These purifiers push water up against a membrane. The water that does not make it through contains the contaminants and is diverted as waste water. While reverse-osmosis systems remove a wide-range of contaminants, including all heavy metals, many pesticides and asbestos, they do not remove trihalomethanes (THMs), radon and VOCs, or pesticides such as lindane and atrazine unless they also have carbon filters attached. They also waste a lot of water " a few gallons for each gallon purified is flushed away as waste water.
Distillers, contrary to popular belief, do not remove all substances from water. Distillers do remove heavy metals, asbestos, nitrates, bacteria, viruses and cysts, but do not eliminate most pesticides, VOCs, chlorine and trihalomethanes (THMs), a group of chemicals which form when chlorine reacts with organic chemicals left in the water by soil and decaying vegetation. THMs may cause miscarriages. In addition, distillation softens water, removing calcium and magnesium, which are beneficial to human health. Softened water is more likely to leach chemicals from storage containers.
Water purifiers that are labeled with "absolute one micron" will filter out cysts that have escaped disinfection by water companies. A word of caution: "Nominal one micron"
will not remove pathogens!
The
National Sanitation Foundation, a nonprofit organization, certifies water filters by the type of contaminants eliminated. NSF Standard 42 is used on filters that remove contaminants that reduce aesthetic quality (taste, smell, color), such as aluminum, chlorine, iron and sediment. NSF Standard 53 is the most comprehensive, used for filters that remove most pesticides, VOCs, cysts, fluoride, most heavy metals and THMs. NSF has a database of filters certified by them.