Selecting just the right drug for a patient is an art form, like chopped liver sculpture.

Sometimes it's based on science, like antibiotic prescribing; once you have the culture and sensitivity report, the decision is pretty much made for you. At other times, picking just the right drug for a patient comes closer to playing roulette. Or, as is the case with drugs commonly used to treat erectile dysfunction (ED), you might take a look at the advertising.

At the moment, there are three phosphodiesterase type 5 inhibitors available to consumers: sildenafil (Viagra, Pfizer), tadalifil (Cialis, Lilly), and vardenafil (Levitra, Bayer). A careful study of the advertising for these three products helps point out the differences.

For example, in one Viagra ad, a man is standing alone. He has a smirk on his face, and two blue protuberances sticking up from his head. These may either represent a devilish appearance, or show that he's wearing a blue hair bow. Now, the advertisers at Pfizer might want to check the meaning of "horn" as a verb. To 'give horns to,' after all, means to cuckold. And that's probably not the symbol they had in mind.

In one Cialis ad, on the other hand, a man is sitting on something, not specified, drinking something (it looks like eggnog), watching a woman take a bath. She doesn't seem to be very serious about it though, since the soap is clearly still in the soap dish at the far end of the tub, and from the color of the sponge she's holding, there's no water in the tub. Again, a word of advice to the advertising department – next time give us a fantasy we can relate to, like a French maid's uniform. Or at least get a bathtub large enough for two. This is just confusing.

Finally, in a Levitra ad, an attractive woman seems to be doing chiropractic manipulations to the neck of a middle-aged man. She appears to be treating him for a stiff neck, which conveys the wrong idea.

What's interesting about the Levitra ad, is that it has a secondary theme of football, including an endorsement from a football player who last played professionally in 1972. Levitra also offers a sweepstakes with a grand prize of a trip for two to the Super Bowl. But how many women are going to treat a trip to a football game as a precursor to a night of sensual romance? After a day watching football, it may not matter whether he has an erection or not.

The fact is that these three drugs are so similar, even their ad agencies can't come up with a good reason for choosing one over the other. The only way is to sit down and discuss your sex life to see which one fits best, pretty much the way you might select a computer. Are you planning to be businesslike, or do you intend to play games?

And, yes, there are differences. For the couple in a hurry, there's no substitute for Levitra. I