From the bizarre pleasure of a spontaneous orgasm to the libido-crushing agony of episodic impotence, antidepressant drugs have long been known to carry the risk of sexual side effects.

Most of these unintended effects are negative; some are just plain weird. And at the forefront of strange results, users have had orgasms while exercising, shopping — and yawning.

This "yawning orgasm" has been reported by patients using Prozac, Zoloft, Wellbutrin and other antidepressant drugs. As many as 5 percent of patients experience the side effect, experts say, though the orgasms may be widely underreported: They have been discovered only "coincidentally during routine side-effect queries," according to one group of researchers, who suspected that patients may be "unwilling to reveal the experience."

"They could be driving their car, and there it is!" said Dr. Norman Sussman, a clinical professor of psychology at the New York University School of Medicine.

Not all out-of-the-blue orgasms were yawn-related. One female patient documented in the Journal of Biological Psychiatry "experienced a three-hour, sudden-onset spontaneous orgasm while shopping." She said the experience was "pleasurable," but "found the experience socially awkward" and stopped taking her medication.

The Exception, Not the Rule

A pill that eases depression and might induce spontaneous orgasms sounds great. But for almost everyone taking antidepressants, the sexual side effects are usually the opposite, resulting in lowered libido and the inability to achieve orgasm (anorgasmia). A lucky few can reach a climax when they least expect it, but many more patients can't get there at all.

"I experienced less pleasure when taking antidepressants, to the point where I would not even think about sex most of the time," said Alex, a 34-year-old engineer from the Pacific Northwest who asked that his last name not be used.

As many as 70 percent of users on selective serotonin re-uptake inhibitors like Prozac, Paxil and Zoloft experience sexual dysfunction, and other classes of drugs can also pose similar problems. Patients are faced with a major dilemma: sex or happiness? The drugs often provide a respite from depression, but it can come at the price of their sex lives.

"It's like saying, 'I'm going to put you on this drug, but there's a 50 percent chance you'll lose interest in sex, and even if you are interested you may not be able to have an ejaculation or orgasm,'" Sussman said.

Some users with SSRI-related sexual dysfunction have taken "drug holidays," leaving their medication in the medicine cabinet for a few days to let their libidos rejuvenate. But because drugs like Prozac take weeks to leave the system, there's no guarantee it will work.

Solving Problems

That's not to say that SSRIs are always bad for your sex life. Even if they're not giving you spontaneous orgasms (don't get your hopes up), they alleviate depression, which is quite a libido-killer on its own.

"If you've been depressed and lose interest in sex, SSRIs can certainly help that," Sussman said. Depression left untreated can cause impotence and retarded libido, so "if you get someone better on an SSRI, a certain percentage will see their sex lives improve."

And it's key that patients find the right combination of drugs in order to minimize sexual side effects that may occur. Because every patient will react differently to given pharmaceuticals, "it's trial and error," Sussman said. "You switch to another [drug] because these things are idiosyncratic." He has even begun prescribing Viagra to help patients regain the orgasms they have lost.

Some short-fused men may even find that the side effect of anorgasmia, or difficulty achieving orgasm, may be beneficial. "There are guys out there who would have been absolutely afraid to have intercourse because of premature ejaculation," Sussman said. "They take SSRIs and they can stand up to anybody, so to speak."