HERSHEY, Pa. – By bedtime, Melissa Ark was so tired she had to decide whether to brush her teeth, floss or wash her face. She had only enough energy for one.

She could barely eat. Her digestive system was so inflamed, most foods caused major discomfort. Even water upset her stomach.

“I would be doubled over in pain just from that water hitting my stomach,” said Ark, 47, of Lower Paxton Township, Pa.

An exercise instructor and nutritionist, Ark had been in exceptionally good health. Now she was being ravaged by Crohn’s disease, a chronic inflammation that usually affects the small or large intestine or both.

A drug widely used to treat heroin addiction would put her back on the road to health.

The experimental treatment being tested at Penn State Milton S. Hershey Medical Center involves naltrexone, a drug available since 1984.

Years ago, researchers noticed small doses of naltrexone seemed to promote healing. Hershey Medical Center gastroenterologist Jill Smith was tapped to spearhead a study.

The first was conducted several years ago and involved 17 people with Crohn’s disease

Eighty-nine percent showed improvement, and 14 went into remission, according to study results published in the American Journal of Gastroenterology.

Based on those results, Smith obtained funding from the National Institutes of Health and a private foundation for a larger, more definitive study.

That study, still under way, has involved about 30 people and will eventually include 44. In another study, Smith will evaluate the effectiveness of the treatment in children ages 6 to 17.

She is optimistic that naltrexone could significantly improve the lives of Crohn’s patients. An estimated 700,000 people in the United States have Crohn’s.

Crohn’s often strikes people in their teens or 20s. Some people never become severely ill, while others have severe medical problems.

A generic drug, naltrexone is cheaper than newer, brand-name drugs. A month’s course of the drug could conceivably cost less than $100.

In addition, naltrexone might cause fewer side effects than anti-inflammatory drugs commonly used to treat Crohn’s, Smith said. Those drugs can suppress the immune system, putting the patient at risk of severe infection and cancer, Smith said.

“We do have some evidence that the naltrexone may actually improve the immune system rather than suppressing it,” she said.

Ark, who was diagnosed with Crohn’s 10 years ago, had previously been involved in a trial of another drug, which didn’t help.

After taking naltrexone for three months, she began to feel better. She has had no side effects.

Ark continues to take naltrexone and is not in complete remission. But she feels closer to how she felt prior to developing Crohn’s.

“Even my worst days are better than my best days were,” she said.

Naltrexone is not widely available to Crohn’s patients. Indeed, considerable hurdles stand in the way.

Naltrexone was approved by the Food and Drug Administration in 1984, but only for treatment of substance abuse, and in a much larger dose than a Crohn’s patient needs.

The drug is available only in 50 milligram pills. Smith’s patients take a specially mixed dose of about 4 milligrams. While physicians could prescribe “off label” use of naltrexone to treat Crohn’s, many would be reluctant to do so, fearing an overdose, Smith said.

Moreover, naltrexone’s status as a generic drug might impede approval for other uses.

New drugs have patent protection for seven years, giving the manufacturer a chance to recoup development costs and earn a profit, Smith explained.

When an approved drug such as naltrexone gets approval for a different use, the protection lasts only three years, so there’s less potential for profit, she said.

The approval application costs $750,000, she said, and the FDA would probably require another, larger study.

Smith believes that factor is making it hard for her to sway a drug company to sponsor trials and apply to get naltrexone approved to treat Crohn’s disease.

Naltrexone is being tested, with promising results, on other illnesses, including HIV and cancer.

At Hershey Medical Center, researcher Ian Zagon believes naltrexone might be beneficial to people with multiple sclerosis. His research so far has involved animals, but he’s trying to obtain funding for trials involving humans.