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Years of study and review are behind every prescription pill.

A little more than 100 years ago, "patent medicines" abounded—tonics or elixirs that claimed to cure diseases and conditions such as cancer, diabetes and weak hearts. These medicines often contained opium, morphine, heroin or cocaine, and they had no proven health benefits.

Unfortunately, the people buying these drugs had no way of knowing what the products did or what was in them. To find out what a drug did—good or bad—a person simply had to take it and wait.

Thankfully, a trip to the pharmacy now isn't nearly as risky. All drugs sold in the United States have to be tested thoroughly for safety and effectiveness before they go on the market.

Where do they come from?

The process of developing a drug generally starts in a laboratory, where scientists follow a lead taken from promising research. Or it can arise from the need for a new drug for a specific disease or condition.

Drug development starts with close observation of the body's functioning, both in good health and when affected by disease. Scientists then puzzle out how the disease affects the body's cells and molecules and try to find a chemical that interrupts the process.

The very first studies, used to find a drug with a chemical effect, are done in test tubes. These preliminary tests are called assays.

Ensuring safety

Drugs that do well in test tube studies are then tested on animals. Animal tests measure:

• How much of the drug makes it into the bloodstream.
• How the body breaks the drug down.
• The type and safety of the chemicals produced when the drug breaks down.
• How quickly the body processes and excretes the drug.

Most drugs don't pass these tests: They're ineffective, unsafe or poorly absorbed.

The human element

With good results from animal studies, the drug's creators can apply to the U.S. Food and Drug Administration (FDA) for permission to test a drug in humans. These tests are called clinical trials.

Phase I clinical trials test the drug's side effects at different doses in healthy volunteers. This helps establish the drug's most common side effects and the link between drug dosage and severity of side effects. Phase I trials generally last several months and include a small number of people.

Phase II clinical trials study the drug's effects in people who have the disease the drug is designed to treat.

In most cases, researchers divide up to several hundred volunteers into treatment and control groups. The treatment group gets the new drug, while the control group gets no treatment, a placebo, a drug known to work or a different dose of the new drug.

After a study period of several months to two years, researchers compare health and disease progress in the two groups.

Phase III clinical trials include a much larger group of people with the disease the drug is designed to treat—several hundred to several thousand. These trials are designed much the same way as the phase II trials but last for up to four years.

Making the call

After these tests and trials, a new drug application can be sent to FDA's Center for Drug Evaluation and Research (CDER). This agency has the final word on which drugs may or may not be sold in the United States.

The application must include information on:

• The results of all testing.
• What the drug is made of.
• How the drug affects the body.
• How the drug is made, processed and packaged.

The CDER also requires a sample of the drug and the labels that will be used for it.

A team of scientists and doctors reviews the application. The final decision is based on the drug's benefit-to-risk relationship—how well it treats the disease compared to its side effects.

It takes less than six months for the CDER to evaluate most "priority" drugs—drugs that offer a clear advantage over available treatments. For most others, it usually takes a year or less.

After approval

FDA continues to monitor prescription drugs after they're on the market through the MedWatch program.

This program tracks serious side effects and interactions reported by doctors, nurses, pharmacists, manufacturers, healthcare facilities and consumers. Based on these reports, FDA may:

• Send letters or alerts to doctors, pharmacists and other healthcare professionals warning them about new safety information (medical alerts).
• Require safety warnings in a prominent place on the drug's label (boxed warnings).
• Require the drugmaker to conduct more studies.
• Inspect the facility where the drug is made.
• Remove a product from the market for good (product withdrawal).

If you suspect a drug of causing a serious side effect or interaction, talk to your doctor about filing a MedWatch report or go to the MedWatch website.

Take as directed

It took decades to form current U.S. drug laws, but they won't help unless you follow your doctor's instructions for taking medicines. Just because a drug is safe for one use doesn't mean it's safe for any others. And make sure to tell your doctor about all the medicines you're taking—it's the only way to avoid potentially dangerous interactions.

Reviewed 12/14/2023