The Food and Drug Administration has long had gaps in data about how people are reacting to medicines that have hit the market. The agency must rely on doctors, patients and drug manufacturers to report troubling side effects, or "adverse events." But it is, at best, an imperfect system.

Now, in an effort to get a fuller understanding of side effects of certain medicines, the FDA is partnering with a networking forum called PatientsLikeMe, which allows people with the same disease or condition to connect with others and share their experiences.

The site, among the largest of its kind, has more than 350,000 members reporting on about 2,500 conditions. That translates to a massive amount of data, which can be sold to pharmaceutical companies, regulators and care providers. But rather than sell that information to the government, the group plans to collaborate with the FDA to develop new methods of finding problems with new drugs.

"There's no one perfect bullet for surveillance," said Ben Heywood, co-founder and president of PatientsLikeMe. "We know it's just another way for patients to have a voice in the market."

The partnership is only in its exploratory phase and expected to last at least three years, but it has the potential to influence how the FDA manages its risk assessment of drugs, which is currently done primarily through clinical trials. The trials only have a limited reach to a drug's users — maybe a few thousand people at best — but patient-generated data could give a more complete picture on side effects by providing more context.

[FDA data show men and women have vastly different adverse reactions to drugs]

So far, the for-profit company has collected more than 110,000 adverse event reports on roughly 1,000 different medications since 2009.

FDA officials said all information provided to the agency will be anonymous, so the agency will not be following up with patients who post information on the website.

The company called the partnership an "unprecedented step" in the post-market surveillance of drugs by the FDA, but this won't be the first time the company has shared data with the agency. PatientsLikeMe first launched its drug safety initiatives in 2008 with a pilot program specifically looking at people living with multiple sclerosis.

Data from PatientsLikeMe will act as a supplement the FDA's already existing post-market reporting systems. The agency uses that data, in part, to make sure manufacturers maintain quality control and to monitor for safety.

But the system remains far from complete.

Just because a bad reaction is reported doesn't necessarily mean it is linked to the medication, and just because there is a side effect associated with a drug doesn't mean it is preventable. Also, while the law requires manufacturers to report adverse reactions to drugs to the FDA, health care professionals and patients must do so voluntarily.

As a result, most reports made to the FDA are completed by manufacturers, not the consumers directly experiencing the effects.

"Any time you rely on self-reporting, it won't be the most robust data," said Tejal Gandhi, president of the National Patient Safety Foundation. "Going to patients is really important. Once you start getting signals, the FDA can figure out if it is a true signal."