Made of Honor, beginning with its flat pun of a title, is another wedding-themed romantic comedy that fizzles when it should fizz. As anyone who has seen the ubiquitous posters knows, Patrick Dempsey (aka Dr. McDreamy) plays the maid of honor (unfortunately not in drag) in this lame, tame variation on My Best Friend’s Wedding. Here, however, there’s never any question that this maid will marry his best friend, Hannah (Michelle Monaghan). Along the way, we’re forced to learn far too much about the onerous responsibilities attending this honorific, with changes of scenery thrown in as palliative.

It starts with a few sparks. A guy wearing a Clinton mask and speaking in a wry Clintonian voice wanders through a drunken party at Cornell in 1998, looking for his Monica. When he enters the darkened dorm room and jumps into bed, he finds Monica’s startled roommate, Hannah, instead. She’s Doris-Day-horrified at the Lothario beneath the mask, Tom (Dempsey), who in turn is fascinated by this straight-talking girl who claims she doesn’t want to sleep with him. (It’s remarkable how young the makeup artists manage to make 42-year-old Dempsey look in this scene.)

Unfortunately, the movie jumps forward ten years, and it’s downhill from there. Director Paul Weiland (City Slickers II) shoots locations here with exclamation marks, so we glimpse the Brooklyn Bridge, Dean & DeLuca, and several Soho restaurants before we see Tom drive up in his sleek convertible. He’s rich from having invented the heat-resistant coffee cup sleeve, lives in a sleek penthouse, and keeps his sex life strictly divorced from his emotional life. The movie suggests that his father (gamely played by the director Sydney Pollack) has not set the best example by marrying six times. It’s a bachelor’s paradise until his best friend since college, Hannah, goes to Scotland on a business trip and becomes engaged to a handsome Scottish duke (Kevin McKidd). Suddenly, Tom’s feelings for the adorable Hannah become more than friendly. His basketball buddies encourage him to follow her and “steal the bride,” and so Soho is replaced by the lush green Scottish countryside, a magnificent castle, and kilts.

Dempsey is far more appealing on “Grey’s Anatomy” than here or in Enchanted. He’s still handsome, but more sad than charming as a romantic lead, and doesn’t convey the same charisma on the large screen. He and Monaghan (Gone Baby Gone), who has a perky, wholesome beauty, share some chemistry, but not enough. They’re not helped by the uninspired screenplay and uneven supporting cast. Kathleen Quinlan appears comatose as Hannah’s mother. The other bridesmaids, especially Hannah’s bitter cousin, are grating when they should be sharp. And Tom’s male friends, especially an ill-conceived nerd who is supposed to be funny because he’s wearing tiny basketball shorts, add nothing by way of comic energy or wit. McKidd (HBO’s “Rome”) is largely wasted in the role of the dashing Scot, but he’s suitably gallant and chiseled.

Everything you’re meant to feel, the soundtrack signals loudly, and the mannered cinematography simply calls attention to itself. Add to this Grandma innocently wearing a sex toy as a necklace and you get the point. Made of Honor is tone-imperfect.