For 15 years, Kae Guardi loved her Depo-Provera, taking injections of the synthetic birth control hormone once every three months and never having to worry about menstruating.
But at age 48, nearing menopause, Gaurdi went off it for eight months and was overwhelmed with severe symptoms: nausea, breast tenderness and fatigue. And the dry heaves were so bad that she went back on the shots.
"I didn't know when they would hit -- usually in the morning or after 5 at night," she told ABCNews.com. "We could be in a restaurant or a ladies room and it would be so embarrassing, I would be crying and gagging so bad."
"I tolerated the drug quite well and that's why I'm surprised at these side effects," said the Endicott, N.Y., secretary. "Actually I liked the drug a lot -- told others how great it was. Now I wouldn't recommend it to anyone."
Guardi is one of 52 women who wrote to ABCNews.com about their experience with Depo Provera contraception injections. Many reported bothersome symptoms when stopping the drug.
Gaurdi's doctors just "shrugged their shoulders" over her complaints. Other gynecologists are also baffled and note that few long-term studies have been done on the hormone.
Produced by Pfizer, Depo-Provera is the brand name for an aqueous suspension of medroxyprogesterone acetate, which is injected every 12 weeks in the woman's buttock or upper arm to prevent ovulation. It is 97 percent effective in typical use.
The drug, which is also used to treat endometriosis, as well as other medical conditions, has had a long safety record since it was first introduced in 1967.
The original manufacturer, Upjohn, was repeatedly denied approval by the Food and Drug Administration in the 1970s, until 1992 when it was allowed to market Depo-Provera in the United States for contraception.
According to Pfizer spokesman Rebecca Hamm, Depo-Provera has been studied in clinical trials up to seven years. Nausea was reported in 1 to 5 percent of women in the clinical trials and dry heaves was not listed as an adverse reaction.
One long-term trial showed a decline in women's bone mineral density during use of Depo-Provera, but after 96 weeks of discontinuation, those losses were reversed.
"Women should discuss with their healthcare providers the risks and benefits of taking Depo-Provera," Hamm told ABCNews.com.
Pfizer also clearly states on its packaging that women should only use Depo-Provera Contraceptive Injection for longer than two years, "if other methods of birth control are not right for you."
"It's been around a long time and mostly used for therapeutic things before contraception," said Dr. Paul Kaplan, a University of Oregon gynecologist. "But the studies have been on its effectiveness and not about long-term use, particularly because it's unusual to be on it for longer than four to six years."
Kaplan directed a 2008 study on synthetic progestins like Depo-Provera that showed a link with vascular disease in premenopausal women.
Synthetic progestins like Depo-Provera have been a boon to women who cannot take estrogen-based pills or other forms of birth control like the IUD.
The injections are also useful for teenagers who may not be "responsible" about remembering to take birth control, according to Kaplan.