The pharma blogosphere is buzzing about what appears to be a new “guerilla marketing” campaign for the over-the-counter allergy drug Zyrtec.

According to one blogger in Boston and another in New York, many of these seemingly handwritten flyers have been seen taped to telephone poles, scaffolds and other post-like structures over the past week. (Click on the image at left for a larger version, courtesy of PharmaGossip.) Some anecdotal sightings have even reported a few of the tabs torn off. The phone number connects to a recorded message touting Zyrtec’s advantages and eventually directs callers to a Zyrtec Web site.

In case it’s not immediately clear, this college-town-style flyer is actually a negative ad attacking rival allergy drug Claritin, which is also sold over the counter. No word yet on whether Zyrtec’s maker — Johnson & Johnson subsidiary McNeil-PPC — is taking responsibility for the campaign, although I’ll let you know if I can find anything out.

Whatever your feelings about consumer-directed drug ads, it’s hard not to admire the cleverness of this approach. Given the increasing pressure on drugmakers from generic competition, Congress and the FDA, it wouldn’t surprise me at all to see other pharmas exploring similarly creative alternatives to traditional drug marketing. Whether it will turn out to be effective is an entirely different issue, and there I have my doubts — although you have to admit that it certainly doesn’t cost much, either.

There’s one more catch: If this scheme is legal, it’s probably only because Zyrtec doesn’t require a prescription, which would necessitate a lengthy disclosure of side effects and other information in any ad. On the other hand, simply omitting the name of the advertised drug might get you around that requirement, too.