Adverse event is a healthcare term that indicates any undesirable and unintended series of events (psychological and/or physical) a patient experiences or could have undergone courtesy therapeutic goods or medical treatment such as hospitalization, surgery, medical product usage, medical test or research, etc. Any patient irrespective of his disease, medical condition, or medical diagnosis can experience adverse events.

Within the drug therapy context, adverse events are also called adverse effects or adverse drug reactions. Extremely serious or complicated adverse events are called ‘never events’ or ‘sentinel events’. However, in most scenarios, the terms ‘adverse event’ and ‘sentinel events’ are used alternatively. Adverse events that could have harmed the patient but were averted in time either by a medical professional or patient are referred to as a ‘near miss’.

Difference Between Adverse Event and Side Effect

Adverse events shouldn’t be confused with side effects as one’s aware of a treatment’s possible side effects; adverse events, on the other hand, are unexpected. Also, an adverse event’s implications are more dangerous and harmful. A patient could experience an adverse effect due to the physician’s or a healthcare personnel’s lack of drug knowledge. Also, adverse events don’t resolve on their own and require medical intervention such as medication or hospitalization.

A side effect is usually known. Typically, a healthcare provider would alert the patient about the possible side effects of administering a drug or undergoing a medical treatment. The effects are not always harmful and they resolve with time. At times, a drug could be administered primarily for its side effects. For instance, Botox was originally intended to address eye-related diseases. The fact that the neurotoxic protein could treat wrinkles was only accidentally discovered. Adverse events, on the contrary, are always undesirable. A side effect can be also termed as ‘mild adverse event’.

Medicines and Devices Causing Adverse Events

Adverse events are usually associated with the medical industry, especially clinical trials and drug therapies. Almost all medications and vaccines could cause adverse events. These medicines include over-the-counter medicines, prescription medicines, and also complementary medicines such as homeopathic or naturopathic preparations, herbal medicines, and nutritional supplements.

The medical devices that could cause adverse effects could range from complex medical equipment to bandages. The devices included are breast implants, blood pressure monitors, condoms, catheters, MRI scanners, lubricating eye drops, syringes, orthodontics (fillings and braces), etc. Problems usually associated with these devices are defective components, labeling or packaging errors, performance failures, and poor design or construction.

Adverse Outcomes

An adverse event’s outcomes can be primarily categorized as predictable and unpredictable. The predictable events are usually dose-dependent and could be categorized as mild, moderate or severe. A mild impact is any discomfort that doesn’t impact the individual’s routine functioning or performance and doesn’t need medical treatment. A moderate impact could render the patient uncomfortable, possibly worsening the condition that the patient already had. Treatment is invariably required.

A severe impact would invariably lead to major symptoms that mitigate the individual from performing routine tasks, needing invasive surgical or medical intervention or hospitalization. And long-term consequences are possible too. Breathing issues, serious blood disorders, convulsions or seizures, permanent disability, congenital anomaly or birth defect (medical product exposure during pregnancy or prior to conception) and fatality are some severe adverse effects.

Unpredictable adverse event reactions are usually not correlated to dosages. They don’t occur too often and could be influenced by drug allergies, intolerances, and other patient-related susceptibility factors.

Adverse Event Documentation

Clinical trials usually furnish information about the several possible adverse outcomes related to a therapeutic good. Product manufacturers (medical device suppliers and pharmaceutical companies), consumers (patients, their family members and lawyers), and healthcare professionals (pharmacists, physicians and nurses) furnish these reports to the state agency. Consumers and healthcare professionals could even report to product manufacturers.

Adverse event collection involves clinicians or researchers detecting events as they happen at a clinical facility. This could comprise chart review, interviewing medical staff and patients, digital searches, direct ward observation and clinically examining patients. Generally, trained experts document the information as per a standard template to ensure data consistency and accuracy. Healthcare providers, reporters, patients, and others must ensure the data is captured completely and in clear clinical language. Also, data should be analyzed and similar syndromes or toxicities should be grouped for easy perusal.

Significance of Reporting Adverse Events

An adverse event not just harms a patient physically, emotionally and psychologically, but also leads to costs incurred for curing or subsiding the adverse effect. Reporting adverse events help discover safety concerns related to an already marketed product. An adverse event helps supervise safety of products that have been approved for public usage. If there is a safety concern with a particular product, the product is evaluated again.

Based on the reevaluation’s outcome, regulatory action could be taken by government medical agencies to enhance product safety and safeguard public health. The measures could be updating the labeling information of a product, restricting its usage, dispensing fresh safety information to public, or getting the product removed from the market.

Unreliable Information

Generally, it’s not certain that the reported medication error or adverse event was courtesy the product. Also, most clinical trials don’t continue long enough to discover adverse outcomes that take time to develop. The sample of patients isn’t large and diverse enough to deduce anything or detect adverse outcomes that rarely occur. Moreover, the sample doesn’t usually comprise different kinds or a mix of people such as children, older individuals, pregnant ladies, or individuals with specific medical conditions.

Proper evidence is not always required to ascertain a particular product causing an event. Also, reports don’t always comprise sufficient detail for properly evaluating an adverse occurrence. In other words, no adverse event report establishes that a particular drug caused the effect. The reaction could have been due to an individual’s underlying disease or other drug(s) being administered concurrently.

Also, not all adverse events relating to a product are reported. Usually, a product with strong marketing invariably gets reported more. At times, multiple reports pertaining to a specific product could come through. Near misses are not recorded. Experts believe tackling adverse events and chances of reducing future occurrences will be more effective only if near misses are also accounted for, along with adverse events. The primary reason why near misses go unreported is people fear dismissal or disciplinary action if they report near misses, which are a lot more common than realized adverse effects.


To achieve and oversee improvements in healthcare sector and patient safety, planning and implementing systematic and standardized adverse event measurement mechanisms are vital. Until systematic methods are there to detect adverse events, developments in patient safety would be difficult to measure reliably.