In January 2016, disaster struck in France when at least six people who were enrolled in a clinical drug trial reportedly had bad reactions to the medication being tested. One person died. Others were hospitalized with severe health problems.

The volunteers were healthy to begin with, which is typical for a Phase 1 trial. Such trials are designed to test safety (not effectiveness) and identify side effects.

It’s not yet clear where that trial went wrong, if it did. But the incident reminds us that when it comes to clinical trials, the treatment or procedure being tested may not always be safe or effective.

If your doctor has suggested joining a clinical trial, or you've thought about it, here is what to know.

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Clinical trials: pros

Clinical trials are at the center of all medical advances, according to the National Institutes of Health (NIH). They look at new ways to prevent, detect or treat disease with new drugs, combinations of drugs, surgical procedures or new devices, or new ways to use existing treatments. Without clinical trials, these advances would not be possible.

Participating in a clinical trial can potentially be lifesaving for sick people. Healthy people who volunteer can learn a lot about their health status in the process.

Clinical trials: cons

Among the possible downsides of joining a clinical trial are these:

  • The treatment may not work as well as the researchers expected, or at all, according to NIH. It may not work even as well as currently available treatments.
  • You may experience side effects. Dropout rates can be high — as high as 30 percent more according to one estimate. One reason for dropouts may be side effects. Often these are temporary or minor, but some can be severe. “In rare cases, participants have been seriously injured or have died of complications resulting from their participation in trials of experimental therapies,” notes an NIH article aimed at seniors. According to breastcancer.org, side effects may be more likely in Phase 1 and Phase 11 trials. (Phase III, the final phase before approval and marketing, aims to confirm effectiveness and monitor side effects.)
  • You may get a placebo . If you do, while you may experience a positive ''placebo effect,'' you won’t get the full benefit of the treatment.
  • You may have to spend a substantial amount of time at a hospital or clinic to fulfill the trial requirements. The trial could last months or years. Extensive paperwork or reporting may be required.

To better protect people enrolled in clinical trials, in 2010 the Food and Drug Administration strengthened its regulations governing trials of new drugs and medications known as biologics. For instance, researchers must report findings that suggest a substantial risk to trial participants within 15 days of becoming aware of the problem. If serious adverse (negative) reactions occur at a higher than expected rate, that must be reported promptly, too.

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What to ask before joining

If you’re considering joining a trial, do some research before you decide. You can read about the trial at www.clinicaltrials.gov.

The NIH, cancer.gov and other health care groups suggest these questions to ask your doctor or the director of the trial:

  • What is the goal or purpose of the trial?
  • Why might this treatment or procedure or device be better than what is available?
  • What time commitment is needed? Is travel involved? Hospital stays?
  • What are my chances of getting the placebo treatment? (You should be informed verbally and in writing of this, advises the Lung Cancer Alliance.)
  • How will I know the treatment works?
  • Will I be informed of the results?
  • Who will oversee my care and tests?
  • What are the common side effects and which are serious enough to need medical attention?
  • If I have questions, whom do I call, before and after working hours and before, during and after the trial?
  • Can you discuss both benefits and risks and tell me how they balance out?
  • Is there any cost to me?
  • What happens if I am injured during the trial? Who pays those costs?
  • Who talks to my insurance company to answer their questions?
  • What happens after the trial is over — do I still get checkups?

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Kathleen Doheny is a Los Angeles journalist specializing in health, behavior and fitness topics.