Pharmacovigilance: how medicine safety is monitored after approval

Pharmacovigilance is the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other medicine-related problem. When a medicine is approved by a regulatory authority, it has usually passed rigorous clinical trials demonstrating that its benefits outweigh its risks. However, clinical trials typically involve only a few thousand carefully selected participants and often last for a relatively short period. Once a medicine reaches the market, it may be taken by millions of people over many years. This real-world use can reveal rare side effects, unexpected drug interactions, or safety issues in specific populations—such as pregnant women, children, or the elderly—that simply did not appear during initial testing. Post-market monitoring is therefore essential to ensure that a medicine's safety profile remains favourable throughout its lifecycle.

Monitoring safety after approval is a continuous process. It relies on a combination of spontaneous reporting by healthcare professionals and patients, formal post-authorisation safety studies, and the global sharing of data. Without this ongoing scrutiny, regulators would be unable to identify emerging risks or take action to protect public health.

Understanding adverse events and reactions

An "adverse event" is defined as any untoward medical occurrence in a patient administered a medicine, but it does not necessarily have a causal relationship with the treatment. For example, if a patient develops a headache while taking a new medication, that is an adverse event; it might be caused by the medicine, or it might be entirely unrelated. When an event is evaluated and confirmed to be caused by the medicine, it is termed an "adverse drug reaction" (ADR). Understanding this distinction is important, as not every negative symptom experienced during treatment is a side effect of the drug itself.

Pharmacovigilance relies heavily on the spontaneous reporting of these events. Healthcare professionals and patients are generally encouraged to report any suspected ADRs, even if they are not certain that the medicine was the cause. Reports of serious reactions, unexpected reactions, and reactions in vulnerable populations are particularly valuable. Patients can assist this process by reading the patient information leaflet to understand expected side effects, but reporting new or unusual symptoms to a healthcare professional ensures they are captured in the safety monitoring system. These spontaneous reports form the raw data that regulators use to monitor safety.

Signal detection and global databases

The primary goal of collecting adverse event reports is "signal detection." In pharmacovigilance, a signal is information arising from one or multiple sources that suggests a new, potentially causal association between a medicine and an adverse event. Because an individual country might only see a handful of cases of a very rare reaction, global collaboration is vital. The World Health Organization (WHO) maintains VigiBase, a global database of suspected adverse drug reactions managed by the Uppsala Monitoring Centre in Sweden. VigiBase pools reports from over 150 member countries.

By analysing this vast pool of data using statistical methods that look for unusually high reporting frequencies, pharmacovigilance experts can detect emerging safety patterns that would be invisible to any single national regulator. Similar databases, like EudraVigilance in Europe, help regional authorities monitor medicine safety. Once a signal is detected, it undergoes further evaluation to determine whether the medicine genuinely caused the reaction and whether regulatory action is required.

How SAHPRA monitors safety in South Africa

In South Africa, the South African Health Products Regulatory Authority (SAHPRA) is responsible for monitoring the safety of medicines after registration. SAHPRA operates a national pharmacovigilance programme that collects, evaluates, and acts on adverse event reports. Both healthcare professionals and the public can submit reports of suspected ADRs to SAHPRA, commonly through the MedSafety app or standard reporting forms. Additionally, pharmaceutical companies, as Marketing Authorisation Holders, are legally required to report any safety concerns they become aware of to the regulator.

SAHPRA is also a contributing member to the WHO Programme for International Drug Monitoring, meaning local reports feed into VigiBase, and local regulators benefit from global data. Consumers using tools like HealthSA to search for medicine registrations can be assured that these products are continually monitored by SAHPRA post-approval. This ensures that the safety of medicines available in South Africa is assessed against both local experience and international standards.

Regulatory responses to confirmed safety signals

When a safety signal is confirmed and the benefit-risk balance of a medicine shifts, regulators have several tools to manage the risk. The most common response is updating the medicine’s package insert or patient information leaflet to include new warnings, precautions, or contraindications. Regulators might also issue safety advisories or "Dear Healthcare Professional" letters to alert doctors and pharmacists to the new information.

In some cases, a medicine may be restricted to certain patient groups, require additional monitoring, or be subject to a Risk Evaluation and Mitigation Strategy. If the evidence ultimately shows that the risks of a medicine clearly outweigh its therapeutic benefits, the regulator may suspend or withdraw the marketing authorisation entirely, removing the product from the market. This dynamic system ensures that medicine approvals are not just a one-time event, but an ongoing commitment to patient safety.