In the appropriate frame of mind, "Loving Couples" may seem like welcome commercial fluff -- the ideal source of relaxation at the end of a hard day or long week.

The plot calls for a coy title along the lines of "Just What the Doctors Ordered." James Coburn and Shirley MacLaine co-star as married doctors: Walter and Evelyn Kirby of Beverly Hills, he a surgeon and she an internist.

After 10 years of marriage they drift apart and into love affairs with younger partners. Although the breakup is lamely contrived, it attempts to obscure expediency with a little novelty: It's Evelyn rather than Walter who first proves unfaithful.

Walter has allegedly provoked his wife by treating her thoughtlessly, but the available evidence is shaky. Dapper, extroverted and prominent, Walter is much in demand, vain enough to enjoy the limelight and inclined to overbook himself, a bad habit that torpedoes simultaneous plans made by Evelyn.

She's especially miffed that he forgets a long weekend vacation and agrees to speak at a medical convention. When she asks why another doctor couldn't pinch-hit for him, Walter is genuinely hurt. The topic is the colon, his baby. "Who else is there?" he plaintively asks.

Curiously, Evelyn doesn't appear to be subject to similar obligations. She appears to be a doctor with a surplus of open dates and too much time on her hands. Although shown on the job, she's closer to the tradition of bored socialite wives like the Dana Wynter character in "Airport."

Screenwriter Martin Donovan lacks an acceptable grievance for the romantic complications he sets in motion. Could the real source of Evelyn's discontent be professional jealousy? It's never acknowledged, but it would make more sense than her humorless peevishness about minor defects in an otherwise charming and affectionate spouse.

At any rate, Evelyn proves susceptible to a rush by a handsome young realtor, Gregg Plunkett, played by Stephen Collins. He happens to be blithely betraying a steady girlfriend, Stephanie Beck, an awkwardly appealing TV weather reporter played by Susan Sarandon. The affair is discovered by Stephanie; depressed and perplexed, she seeks advice from Walter, who is astonished to learn that he's in the same boat.

A second affair blossoms out of the mutual melancholy of the deceived partners. The rearranged couples accidentally confront each other at the same weekend rendezvous. Deception no longer being necessary, the men exchange residences, and it becomes simply a matter of time before Donovan can manuever his quartet into reconciliations with their original mates.

The men prove more appealing company than the women, perhaps because Donovan feels less inhibited about kidding their pretensions and foibles.

Although Evelyn appears to be indulging a second adolescence with Gregg, I rather fear that we're supposed to regard it as a sign of newfound independence when she learns to boogie the night away and begins wearing T-shirts with slogans like "Under New Management" and "Dance Your Buns Off, Doc."

In a similar respect, Stephanie seems to be Making Progress when she takes a tentative step from weather bulletins to bubbly soft featurettes.

The men emerge as funny sexual rivals. Walter is the most ingratiating role Coburn has had in many years, and he outshines the other attractive members of this ensemble, sometimes by flashing those prodigious teeth with devastating comic effect.

Collins, smoothly exaggerating his own creamily good-looking presence, seems exactly the right type to provoke jealous disparagement from Coburn, who can't resist taking sarcastic potshots at the young interloper.

In fact, the most convincing and amusing human response in the film is Coburn's resentment of Collins. He persuades you that Walter is sincerely offended and mystified by the attraction this sleek, irresponsible pup seems to hold for his wife. He doesn't get it -- and he's got a point.

The writer seems to have trouble imagining what Evelyn and Gregg might say to each other. On numerous occasions their intimate scenes turn into picturesque filler backed by saccharine ballads -- the sort of audiovisual interludes that appear to be inserted so the audience can slip away to the concession stand or bathroom without missing any exposition.

Although so much recycled romantic comedy confetti, the movie is attractively cast and given a crisp, bright finish. There are fringe benefits: the characters live well and frequently step out to fashionable spots, providing the sort of luxurious amenities that help to make an artificial entertainment more ingratiating.

Sally Kellerman does a formidable supporting bit as a Beverly Hills nympho who seduces Collins while being shown house and then keeps popping up like a bad penny.

The script has its moments, scattered as they are. There's a delightful situation in which Coburn is apprehended staking out his own house by Beverly Hills patrolmen. The Walter-Stephanie affair is wrapped up with an ingenious kiss-off, set outside a movie theater. Subterfuges this good tend to defy invention, so Donovan probably transposed it straight from someone's real-life romantic denouement. It's a situation that should haunt insecure lovers for the rest of their moviegoing lives.