When a new drug hits the market, the work isn’t done. In fact, the real test of safety begins after approval. Pre-clinical trials involve a few thousand patients under tight control-mostly healthy adults, carefully selected, and monitored in ideal conditions. But real life? It’s messy. People take multiple medications. Seniors, pregnant women, kids, and those with chronic conditions use these drugs daily. That’s where post-marketing surveillance comes in. It’s not optional. It’s required. And tracking it properly can mean the difference between catching a dangerous side effect early-or missing it until it’s too late.
Why Post-Marketing Studies Matter
Before a drug gets approved, clinical trials rarely include more than 5,000 people. That’s not enough to catch rare side effects. A reaction that happens in 1 out of 10,000 patients won’t show up in a trial of 3,000. But once millions start taking the drug? That’s when problems emerge. That’s why regulators like the FDA and EMA require companies to keep watching after approval.
These studies aren’t just paperwork. They’re active monitoring systems designed to find hidden risks: new side effects, interactions with other drugs, long-term damage, or even unexpected benefits. For example, in 2022, the EMA found that 28% of serious reactions linked to certain heart medications were only visible in elderly patients-people who made up just 15% of original trials but 43% of actual users. Without post-marketing studies, those risks would’ve stayed hidden for years.
The Three-Phase Tracking Process
Tracking post-marketing studies isn’t random. It follows a strict, regulated three-phase process.
Phase 1: Planning - Right after approval, drug companies must submit a detailed safety surveillance plan. This includes how they’ll collect data, who will report side effects, and what risk-reduction steps they’ll take-like updated warning labels, patient guides, or restricted distribution programs. These aren’t suggestions. They’re legally binding commitments.
Phase 2: Reporting - Companies must submit periodic safety reports every few months or years, depending on the drug’s risk level. These reports pull data from multiple sources: spontaneous reports from doctors and patients, clinical studies, insurance claims, and electronic health records. The FDA’s FAERS database alone holds over 30 million reports as of 2023. That’s not just a number-it’s a live stream of real-world drug experiences.
Phase 3: Reevaluation - Every 4 to 10 years after launch, regulators require a full recheck of the drug’s safety, effectiveness, and quality. If new data shows risks outweigh benefits, the drug can be restricted, relabeled, or pulled from the market. Between 2018 and 2022, 87% of safety actions taken by the FDA were simple label updates. But 9% involved direct letters to doctors, and less than 1% led to full withdrawals. Still, even one withdrawal saves lives.
Key Tools for Tracking: FAERS and Sentinel
Two major systems do the heavy lifting in the U.S.: FAERS and Sentinel.
FAERS (FDA Adverse Event Reporting System) is the oldest and most widely used. It’s a voluntary reporting system where doctors, pharmacists, patients, and manufacturers can submit reports of side effects. It’s not perfect-reports are often incomplete, and many go unsubmitted. But it’s the first line of defense. In 2022, 63% of all safety signals came from spontaneous reports in FAERS.
Sentinel System is the newer, more powerful tool. Instead of relying on voluntary reports, Sentinel analyzes real-world data from over 300 million Americans. It pulls from insurance claims, hospital records, and electronic health records. In 2023, it expanded to include detailed EHR data from 24 million patients across six major health systems. That means it can see not just that a patient took a drug, but what other conditions they had, what labs were abnormal, and whether they were hospitalized.
Together, these systems catch different types of risks. FAERS finds rare, unexpected reactions. Sentinel finds patterns across large populations. One reports what happened. The other asks: Why?
Global Systems: What Other Countries Do
The U.S. isn’t alone. Every major country has its own system.
In the UK, the Yellow Card scheme collects reports from healthcare workers and patients. In 2022, they received over 76,000 reports-a 12% jump from the year before. Canada’s Canada Vigilance Program got nearly 29,000 reports in the same period. The EU uses EudraVigilance, which is getting an AI upgrade in 2025 to automatically flag suspicious patterns.
These systems don’t work in isolation. The WHO is building a global network to share data across 100 countries by 2027. Why? Because a side effect that shows up in Japan might be missed in the U.S. if the population is different. Global sharing helps catch problems faster.
What Goes Wrong? The Biggest Challenges
Even with all these systems, tracking isn’t easy. Here’s where things break down:
- Delayed studies - Between 2015 and 2022, 72% of FDA-mandated post-marketing studies ran behind schedule. The average delay? Over two years. Why? Poor patient recruitment, slow data access, and lack of resources.
- Data gaps - Sentinel can’t see everything. Insurance claims don’t tell you why a drug was prescribed, what lab results were abnormal, or whether a patient was actually taking it as directed. That’s why some experts say Sentinel isn’t enough on its own.
- Reporting fatigue - Doctors are busy. Patients don’t know how to report. Many side effects go unreported. One study found that for every serious adverse event, only 1 in 10 gets officially documented.
- False signals - Algorithms can overreact. In 2018, 34% of flagged safety signals turned out to be false alarms. By 2023, improved AI and statistical methods brought that down to 19%. But it’s still a problem.
Companies struggle too. A 2022 survey found that 68% of pharmaceutical firms had trouble meeting FDA deadlines because data systems didn’t talk to each other. Hospitals, pharmacies, insurers-each uses different software. Getting clean, consistent data across all of them? That’s a nightmare.
How to Do It Right: Best Practices
If you’re responsible for tracking post-marketing studies-whether you’re at a pharma company, hospital, or regulatory agency-here’s what works:
- Use automated alerts - Set up systems that flag missed deadlines, unusual spikes in reports, or protocol deviations. Don’t wait for quarterly reviews.
- Build cross-functional teams - Pharmacovigilance isn’t just for safety experts. You need data scientists, clinicians, IT staff, and legal advisors working together. The industry standard? One dedicated specialist for every $500 million in annual drug sales.
- Track your timeliness - Use the Post-Marketing Study Timeliness Index (PMSTI). Measure how many studies finish on time. If your rate is below 80%, something’s broken.
- Integrate real-world data - Don’t just rely on FAERS. Connect to EHRs, registries, and claims databases. The more sources you use, the clearer the picture.
- Train reporters - Educate doctors, nurses, and patients on how and why to report side effects. Simple guides, quick forms, and mobile apps help.
The Future: AI, Genomics, and Global Networks
The next five years will change everything.
The FDA’s Sentinel Common Data Model Plus (SCDM+), launching in 2024, will add genomic data to the mix. Imagine knowing that a drug causes liver damage only in people with a specific gene variant. That’s the future.
AI is getting smarter. Pilot projects with Large Language Models showed a 42% improvement in detecting safety signals from unstructured EHR notes-like doctor’s free-text comments. But there’s a catch: AI also generates 23% more false positives. So human review still matters.
And globally, the WHO’s data-sharing initiative will let countries pool signals. A rare reaction spotted in Brazil could trigger a warning in Germany before it even reaches the U.S.
What’s clear? Post-marketing surveillance is no longer passive. It’s active, real-time, and data-driven. The drugs we take today are safer because of it. But only if we track them well.
What Happens When You Don’t Track?
Look at history. Thalidomide in the 1950s. Vioxx in the 2000s. Both caused thousands of injuries before being pulled. Both were approved under less rigorous systems. Today, those failures are why we have FAERS, Sentinel, and mandatory post-marketing studies.
Skipping or delaying tracking isn’t just risky-it’s irresponsible. Every missed report, every delayed study, every unconnected database increases the chance that someone will be harmed because no one was watching.
The system isn’t perfect. But it’s the best tool we have. And if you’re part of it-whether you’re reporting a side effect or managing a safety plan-you’re not just doing your job. You’re protecting lives.
What is the difference between FAERS and Sentinel?
FAERS is a voluntary reporting system where doctors, patients, and companies submit adverse event reports. It’s good for spotting rare, unexpected reactions but relies on incomplete data. Sentinel is an active surveillance system that analyzes real-world data from insurance claims and electronic health records of over 300 million Americans. It finds patterns across large populations and can track drug use in context-like other medications or health conditions-but can’t see detailed clinical notes unless linked to EHRs.
How long do post-marketing studies usually take to complete?
The FDA typically requires post-marketing studies to be completed within 3 years. But between 2015 and 2022, the median completion time was 5.3 years. Delays happen due to slow patient recruitment, data access issues, and lack of resources. About 72% of studies missed their deadlines during that period.
Who reports adverse drug reactions?
Healthcare professionals (doctors, nurses, pharmacists), patients, and drug manufacturers are all required or encouraged to report adverse reactions. In the U.S., reports go into FAERS. In the UK, they go to the Yellow Card scheme. In Canada, to the Canada Vigilance Program. Patients can report directly through online portals or phone lines set up by regulators.
What actions can regulators take based on post-marketing findings?
Regulators can update drug labels with new warnings, issue "Dear Health Care Professional" letters, require Risk Evaluation and Mitigation Strategies (REMS), restrict distribution, or withdraw the drug entirely. Between 2018 and 2022, 87% of safety actions were label updates, 9% were letters to doctors, 3% involved REMS changes, and less than 1% led to market withdrawal.
Are post-marketing studies mandatory?
Yes. In the U.S., the FDA requires post-marketing studies for many new drugs, especially high-risk ones like cancer treatments, biologics, and drugs for rare diseases. The 21st Century Cures Act increased these requirements by 37% between 2017 and 2022. Companies must submit study plans and meet deadlines-or face regulatory penalties.
How do pharmaceutical companies track their own post-marketing studies?
Companies use centralized pharmacovigilance platforms that integrate data from FAERS, EHRs, clinical trials, and global databases. They set up automated alerts for missed deadlines, unusual safety signals, or protocol deviations. Teams of pharmacovigilance specialists monitor reports daily and coordinate with IT, legal, and regulatory departments to ensure compliance and timely reporting.
Can AI replace human reviewers in post-marketing surveillance?
No-not yet. AI tools like Large Language Models can analyze unstructured data like doctor’s notes and flag potential signals 42% more accurately than traditional methods. But they also generate more false positives (23% higher). Human experts are still needed to review findings, understand clinical context, and decide if a signal is real. AI supports, but doesn’t replace, human judgment.
Next Steps: What You Can Do
If you’re a healthcare provider, start reporting side effects-even if you think it’s minor. Every report adds to the puzzle.
If you’re a patient, know how to report. Visit your country’s drug safety website. Fill out a form. It takes five minutes. You might help prevent someone else’s harm.
If you work in pharma or health IT, invest in integrated data systems. Break down silos. Connect your databases. Automate alerts. Track your PMSTI. Don’t wait for a crisis to fix your process.
Drug safety doesn’t end at approval. It only begins there.