Paxil. Zoloft. Nexium. Vioxx. Viagra. Ever wonder how pharmaceutical and biotech companies come up with names for their bestselling drugs? Is there any logical method to the maddening mix of vowels and double consonants? And what's with all those Z's and X's, anyway?

James Singer, president and chief creative officer of NameBase/MediBrand, spends all day coming up with drug names that roll easily off the tongue and stick in the minds of doctors and patients. Before starting his own firm, Singer worked for the New York branding giant InterBrand, where he helped to conjure up the brand name for the antidepressant fluoxetine. You know it better as Prozac.

We asked Singer to take us through the drug-naming process.

TSC: Is there some kind of drug-naming rulebook, or are you free to use your imagination?

Singer: There aren't any set rules for drug brand names. In fact, most have nothing at all to do with the actual chemical compound or the disease. But it is very important that we avoid any confusion with other drug names. When we come up with a drug name, we have to be extra careful to make sure that it sounds and looks different enough from another drug. Patient safety is crucial.

TSC: So, what are the ingredients for a blockbuster drug name?

Singer: Basically, a good drug name should sound effective. It should be euphonic, which means it should be easy to say and write. And, of course, you want it to be memorable.

TSC: OK, so take us through Prozac. Where did that name come from?

Singer: Again, Prozac has nothing to do with the chemical compound or its indication. It's just a good-sounding name. The word starts with "pro," which implies something positive. The letter P is also what we call a "plosive," which is a strong sound that seems to explode forcefully from the mouth. Studies have shown that brand names that start with "plosive" letters like P, T, K or C are more effective. Think about Coca-Cola, Compaq or Kodak and you get the idea.

TSC: Do all drug names need to have an X or Z?

Singer: (Laughing) No, but those letters are what we call fricatives. They're very fast sounding. In the case of Prozac, it makes people feel like the drug is fast-acting, even though, in reality, it's not.

TSC: That explains the flood of X's and Z's in drug names.

Singer: Right. The "Z" sound, whether it's spelled with a Z or an X, has been very popular for a while. But we're starting to get pretty cautious about using them because they're not very unique anymore. There are just a slew of these out there right now, which can hurt when you're trying to keep your drug name differentiated.

TSC: But didn't you just come up Xenical, the weight-loss drug, for Roche?

Singer: Yeah, but we'd been working on that one for a long time, before the sound became so popular.

TSC: Consumers are bombarded with TV and magazine ads for brand-name drugs these days. Has this new emphasis on direct-to-consumer drug advertising impacted your business?

Singer: Definitely. The best way to get a drug prescribed is to have a patient go to his doctor and ask for it. Years ago, drug brand names were more clinical, but today, drug companies really want names that are sharper and more memorable.

TSC: Spiffy-sounding drug names definitely stick in consumers' minds, but what can you do to improve doctor's handwriting. How do pharmacists know what the doctor ordered anyway?

Singer: (Laughing) Actually, part of our job is to study prospective drug names on doctors and pharmacists to make sure that there aren't any safety problems or confusion with prescriptions. But believe it or not, we're finding that a lot of doctors are now beaming prescriptions electronically using personal digital assistants.

TSC: So, no more problems with lousy doctor handwriting?

Singer: (Laughing) I guess not.