Decades ago, to prepare for a colonoscopy, patients first had to clean out their colons using laxatives such as castor oil or magnesium citrate, sometimes over several days. It wasn't pleasant.

Things improved in 1984 with the introduction of a powder-based solution that patients could drink the day before a colonoscopy. The colon-cleansing drink, called GoLYTELY, tastes nasty but "turned 3 1/2 days of torture into 3 1/2 hours of torture," says gastroenterologist Jack Di Palma, a professor of internal medicine at the University of South Alabama College of Medicine.

The prep for a colonoscopy, a procedure in which a physician snakes a flexible tube through the colon to get a camera's-eye look at the organ's interior, remains perhaps the biggest impediment to screening. So the approval last year of a far less sickening prep option for patients was welcome news.

Cleansing the colon beforehand is critical to identifying and removing polyps, often a precursor to cancer, during the procedure. Over the years, several newer-generation prep solutions have become available, each with advantages and disadvantages, and others — including those in the form of flavored shakes and food bars — have been tested but not yet approved.

The solutions that most patients drink clean out the colon, but patients have to ingest copious amounts — four liters, or a little more than a gallon — and the taste is still pretty terrible.

Physicians now recommend that patients split the dose in two, half taken the day before and the rest several hours before the procedure.

"We tell people to chill it, sip it through a straw, hold their nose, chew gum in between or suck hard candies," says Louis Korman, a semiretired D.C.-area gastroenterologist. "Everyone hears the stories about how horrible the preparation is. The prep is what everyone remembers, and it represents a disincentive to getting a colonoscopy."

But last year — in what experts believe could end the dread that keeps many people from this important screening — the Food and Drug Administration approved a regimen of pills, Sutab, that studies show works just as well as the liquid solutions — without the vile flavor. It's a 24-tablet regimen: 12 pills the day before and 12 the next day, several hours before the procedure.

Patients still must drink lots of water, a total of 48 ounces the first day and another 48 ounces the next day. But at least plain water is tasteless.

"The thing that is great about Sutab is that it takes the issue of the taste away," says Douglas K. Rex, distinguished professor emeritus of medicine at the Indiana University School of Medicine. "You're still going to have to sit on the toilet, but not having to drink something that tastes awful is a big advantage."

Oncologist Arif Kamal, an associate professor of medicine at Duke University, agrees. "This is a good option for those for whom taste is an issue," says Kamal, who is also chief patient officer at the American Cancer Society. He also points out simpler alternatives to full-blown colonoscopies for patients who are at average colon cancer risk, including at-home screening tests for blood and altered DNA that suggest the presence of cancer.

"The pros: It's more convenient to do it at home," Kamal says. "The cons: You still have to sample your own stool. Also, the frequency is more often - every two to three years," compared with a seven-to-10-year interval for colonoscopies. Most insurance plans, including Medicare, cover these.

"Virtual" colonoscopies also are available, although patients still must do the prep, and certain "flat" polyps are more easily seen in conventional colonoscopies, experts say. Virtual colonoscopies are not at-home procedures, as they involve imaging the colon, and insurance coverage is spotty. They are covered only under special circumstances, such as when a conventional colonoscopy cannot be completed for some reason.

The American Cancer Society now recommends that people 45 and older at average risk for colon cancer undergo screening. This is a change from previous guidelines that recommended screening for only those 50 and older at normal risk.

Excluding skin cancers, colorectal cancer is the third-most commonly occurring cancer in the United States, according to the American Cancer Society, which projects an estimated 106,180 new cases of colon cancer this year and 44,850 cases of rectal cancer. About 7 in 10 U.S. adults ages 50 to 75 are up-to-date on colonoscopy screening, according to the Centers for Disease Control and Prevention. Experts believe prep avoidance probably is one of the major reasons the remainder are not.

The new pills could change that, but they have a downside.

Many insurance drug plans won't cover them, and their out-of-pocket price can be $120 or more. (It cost a friend of mine in Florida $150 after her insurance plan denial and — after mine also refused — I paid $60 using a discount coupon my doctor obtained from Sebela Pharmaceuticals.)

"For people who won't get a colonoscopy because of the nasty tasting prep, it could be a game changer — if they can afford it," says gastroenterologist Clement Boland, retired professor of medicine at the University of California at San Diego School of Medicine. "That's ridiculous. It shouldn't be that expensive. It's just salt [sodium sulfate, magnesium sulfate, potassium chloride], not something fancy like monoclonal antibodies."

Experts say the most likely reason for the insurance denials is that the pills are new and aren't yet proved to be an advance over less expensive alternatives. "An insurance company will say: 'Well, if it's equivalent, we'll just cover the cheaper one,' " Kamal says.

Many gastroenterologists coping with patient prep reluctance regard this as backward thinking. "The insurance companies try very hard to force people into using the generic products, which are not tolerated very well," Rex says. "When it comes to prep, efficacy is not the issue. From the patient's perspective, it's tolerability. That is really important to patients."

Several major insurance plans cover the pills, including some in Medicare Part D, says John McGowan, head of research and development for gastroenterology at Sebela Pharmaceuticals.

Because others do not, however, it probably is a good idea to check with your own individual plan to determine whether the pills are covered.

For those who lack insurance or whose plans won't cover the pills, McGowan suggests checking sutab.com/savings on his company's website for ways to save. Also, the company provides free samples and discount coupons to physicians for patients who cannot afford the pills, he says.

He acknowledges that the cost can be a barrier for some patients. Nevertheless, "in the event that a patient cannot properly complete the liquid preparation, a colonoscopy must be repeated, in which case, the additional upfront, out-of-pocket costs for Sutab would be worth it," he says.

The newest pills should not be confused with earlier tablets, made mostly of sodium phosphate, which the FDA found in 2006 caused serious kidney damage in some patients. While still on the market, the old pills are rarely used today, experts say.

"The newer ones have sodium sulfate, and are safe," Rex says, stressing that patients still must drink the recommended amounts of water to avoid dehydration. "You don't want to drink the bad tasting stuff, but you have to drink something," he says.

Di Palma, who conducted the Sutab study, says he has tried all the preps and used them for his own colonoscopies.

"I've had five colonoscopies, and Sutab was the easiest one yet," he says.