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Side effect

A side effect is any unintended response to a medication or medical treatment that occurs alongside its primary therapeutic purpose, potentially ranging from minor and transient issues like drowsiness or upset stomach to severe, life-threatening reactions such as organ damage or allergic responses.^[1]^[2] These effects can be predictable and dose-related or arise unpredictably due to individual factors, and while some may resolve on their own after discontinuation, others require immediate medical intervention.^[3] In clinical contexts, side effects are distinguished from the drug's intended action but are integral to pharmacovigilance, as they influence treatment decisions and regulatory approvals.^[4] The study and management of side effects fall under adverse drug reaction (ADR) monitoring, where organizations like the World Health Organization define them as unintended pharmacological effects at normal doses, encompassing both harmful and occasionally beneficial outcomes.^[5] During drug development, side effects are identified through rigorous clinical trials, but many only emerge post-approval via real-world use, prompting systems like the FDA's MedWatch program for voluntary reporting by patients and providers.^[2] Common causes include drug interactions with other medications, food, or underlying health conditions, with prevalence varying by drug class— for instance, antibiotics often cause gastrointestinal upset, while chemotherapy agents may lead to broader systemic impacts.^[6]^[7]^[8] Addressing side effects typically involves strategies such as dosage reduction, therapeutic substitution, or adjunctive therapies to alleviate symptoms while preserving efficacy, emphasizing the balance between benefits and risks in personalized medicine.^[9] Ongoing research focuses on predictive modeling and genomic testing to anticipate and minimize these effects, reducing the global burden of adverse drug events, which represent a significant global health burden and contribute substantially to healthcare costs.^[10] Patient education plays a crucial role, empowering individuals to recognize and report symptoms early, thereby enhancing overall drug safety profiles.^[11]

Definition and Basics

Definition

In pharmacology and medicine, a side effect is defined as any unintended or secondary effect of a drug, treatment, or medical procedure that occurs beyond its primary therapeutic goal.^[1] This encompasses effects that may arise from the drug's pharmacological properties at standard doses, distinguishing them from the intended outcome such as symptom relief or disease modification.^[5] The term "side effect" first appeared in general usage in 1814 to describe subsidiary consequences of actions, but its application in medical and pharmacological contexts emerged in 1939 to characterize non-target outcomes of therapeutic interventions.^[12]^[13] Side effects differ from the primary effect in that they manifest concurrently or subsequently to the desired action, often at the same therapeutic dose, and are typically predictable based on the drug's mechanism.^[3] While many side effects are benign or manageable, some qualify as adverse reactions when they pose harm, though this classification is explored further in dedicated contexts.^[2]

Intended vs. Unintended Effects

In pharmacology, effects of a medication are classified as intended or unintended based on their alignment with the therapeutic purpose for which the drug is prescribed. Intended effects, also known as therapeutic effects, are those that achieve the primary goal of treatment, such as pain relief from an analgesic like aspirin.^[5] In contrast, unintended effects, often termed side effects, are secondary outcomes arising from the drug's causal mechanisms that were not the reason for its administration, such as drowsiness or gastrointestinal upset from the same analgesic.^[5] This classification hinges on the prescriber's intention and the intervention's inherent pharmacological properties, where side effects are explicitly defined as unintended consequences stemming from the drug's action.^[5] The designation of an effect as intended or unintended can shift depending on the therapeutic context, illustrating the relativity of this classification. For instance, the vasodilatory action of minoxidil was originally intended for treating severe hypertension, but its promotion of hair growth was initially an unintended side effect observed in patients.^[14] Subsequent recognition of this effect led to its reformulation and approval as a topical treatment for androgenetic alopecia, where hair growth became the intended therapeutic outcome while hypotension emerged as a potential side effect at lower doses.^[15] Similarly, immunosuppressive effects of drugs like corticosteroids are intended in organ transplantation to prevent graft rejection but may manifest as unintended side effects, such as increased infection susceptibility, when the same agents are used primarily for anti-inflammatory purposes in other conditions.^[16] These contextual variations underscore that an effect's status is not inherent to the drug but determined by the clinical indication and user intent.^[5] In clinical practice, this distinction guides physicians in prescribing by requiring a careful evaluation of the intended benefits against the potential unintended risks to optimize patient outcomes.^[17] For example, when selecting an antihypertensive, a clinician might favor a drug with strong intended blood pressure-lowering efficacy despite known unintended metabolic side effects, provided the overall benefit-risk profile supports its use in the patient's specific health context.^[18] This assessment involves integrating evidence from clinical trials, patient history, and regulatory data to ensure that the therapeutic gains outweigh any secondary harms, thereby informing informed consent and monitoring strategies.^[17]

Classification

Adverse Side Effects

Adverse side effects, also known as adverse drug reactions (ADRs), refer to unintended and harmful responses to a medication that occur at doses normally used for prophylaxis, diagnosis, or therapy. These effects can range from mild discomforts, such as nausea or headache, to severe outcomes like organ damage or anaphylaxis, often necessitating discontinuation of the drug or medical intervention. Unlike intended therapeutic actions, adverse effects arise from the drug's interaction with the body in unanticipated ways, potentially impacting patient safety and treatment adherence. Classification of adverse side effects by severity helps in clinical assessment and management, with standardized scales providing a framework for grading their intensity. The Common Terminology Criteria for Adverse Events (CTCAE), developed by the National Cancer Institute, categorizes effects into five grades: Grade 1 (mild; asymptomatic or mild symptoms, no intervention needed), Grade 2 (moderate; minimal intervention required), Grade 3 (severe; medically significant but not immediately life-threatening), Grade 4 (life-threatening; urgent intervention indicated), and Grade 5 (death related to the adverse event). This grading aids healthcare providers in weighing risks against benefits and guiding regulatory decisions. A key classification of ADRs distinguishes between Type A (augmented) reactions, which are predictable, dose-related, and common (e.g., gastrointestinal upset from antibiotics), and Type B (bizarre) reactions, which are unpredictable, idiosyncratic, and often immune-mediated (e.g., anaphylaxis).^[19] Common categories of adverse side effects include allergic reactions, toxicity, and organ-specific damage. Allergic reactions encompass hypersensitivity responses, such as rashes, urticaria, or anaphylaxis, triggered by immune-mediated mechanisms to otherwise tolerated drugs. Toxicity refers to dose-dependent harm from excessive drug exposure, leading to symptoms like gastrointestinal distress or neurotoxicity, often due to impaired metabolism. Organ-specific damage, exemplified by hepatotoxicity (liver injury causing elevated enzymes or failure) or nephrotoxicity (kidney impairment), targets particular systems and may result from direct cellular toxicity or idiosyncratic responses. These categories highlight the diverse pathways through which adverse effects manifest, underscoring the need for vigilant monitoring.

Therapeutic Side Effects

Therapeutic side effects are unintended secondary effects of a medication that confer additional health benefits, distinct from the drug's primary therapeutic purpose. Unlike adverse effects, these can be harnessed for new medical applications, often through the process of drug repurposing. In pharmacology, such effects arise from off-target interactions with biological pathways, providing opportunities to expand a drug's indications without the need for entirely new development.^[20]^[1] A prominent historical example is minoxidil, developed in the 1970s as an oral vasodilator for severe hypertension. During clinical trials, researchers observed hypertrichosis—excessive hair growth—as an unintended side effect in patients, particularly on the face, scalp, and extremities. This observation, initially noted in 1971, led to targeted studies on its potential for treating hair loss. By reformulating minoxidil as a topical solution and conducting dedicated trials, it was approved by the FDA in 1988 for androgenetic alopecia, transforming an antihypertensive into a leading therapy for baldness.^[21]^[15] The process of identifying therapeutic side effects typically begins with clinical observation during trials or routine patient care, where unexpected benefits are documented and hypothesized. Subsequent steps involve preclinical validation to elucidate mechanisms, followed by focused clinical studies to confirm efficacy and safety for the new indication. Post-marketing surveillance systems, such as those monitored by regulatory agencies, further aid detection by aggregating real-world data. This iterative approach, often driven by serendipity, has enabled rapid repurposing while minimizing development timelines and costs compared to de novo drug discovery.^[22]^[23]

Mechanisms and Causes

Pharmacological Mechanisms

Side effects in pharmacology often arise from unintended drug-receptor interactions, where a medication binds to non-target receptors, triggering physiological responses beyond its therapeutic intent. For instance, first-generation antihistamines like diphenhydramine can cross the blood-brain barrier and bind to histamine H1 receptors in the central nervous system, leading to sedation as an off-target effect. This off-target binding occurs due to structural similarities between target and non-target receptors, allowing the drug to interact with multiple sites in the body, which can disrupt normal signaling pathways such as those involving G-protein coupled receptors or ion channels. Metabolic pathways play a critical role in generating side effects through the biotransformation of drugs into active or toxic metabolites, primarily mediated by hepatic enzymes. The cytochrome P450 (CYP450) family, including isoforms like CYP3A4 and CYP2D6, oxidizes many xenobiotics, sometimes producing reactive intermediates that cause cellular damage, such as hepatotoxicity from acetaminophen's NAPQI metabolite. These enzymes exhibit polymorphism and substrate specificity, leading to idiosyncratic toxicities when metabolism shifts toward harmful byproducts rather than detoxification. Inhibition or induction of CYP450 by co-administered drugs can further amplify these risks, altering metabolite profiles and exacerbating side effects. Dose-response relationships underpin the emergence of side effects, as therapeutic doses maintain efficacy within a narrow window, while higher exposures exceed safety thresholds, activating adverse pathways. Conceptually, the dose-response curve illustrates a sigmoidal progression where low doses yield minimal effects, therapeutic levels achieve desired outcomes, and supratherapeutic doses provoke toxicity through receptor saturation or metabolic overload. Side effects typically manifest on the ascending or plateau phases of this curve, highlighting the importance of therapeutic indices—the ratio of toxic to effective doses—to predict and mitigate risks. Individual factors can modulate these curves, as explored in related sections on patient-specific influences.

Patient-Specific Factors

Patient-specific factors play a crucial role in determining the occurrence, severity, and type of side effects experienced from medications, as individual biological, demographic, and environmental variations can significantly alter drug responses. These factors introduce variability beyond the inherent properties of the drug itself, influencing how it is processed, tolerated, and interacts within the body. Understanding these influences is essential for personalized medicine approaches that aim to minimize adverse outcomes. Genetic variations, particularly in pharmacogenomics, substantially affect drug metabolism and the risk of side effects. Polymorphisms in the cytochrome P450 2D6 (CYP2D6) gene, for instance, lead to distinct metabolizer phenotypes—such as poor, intermediate, extensive, or ultrarapid—that alter the activation or clearance of substrates like antidepressants, opioids, and beta-blockers. For drugs inactivated by CYP2D6 like metoprolol, poor metabolizers experience elevated plasma concentrations of the parent drug, increasing the likelihood of adverse reactions such as enhanced hypotensive effects. For prodrugs like codeine that require CYP2D6 for activation to morphine, poor metabolizers have reduced efficacy due to insufficient active metabolite formation, along with potentially more codeine-related side effects from higher parent drug levels. Conversely, ultrarapid metabolizers of such prodrugs may produce excessive active metabolite, increasing toxicity risks, as seen with codeine leading to morphine overdose.^[24]^[25] These genetic differences underscore the importance of genotyping in predicting side effect risks for CYP2D6-metabolized drugs. Demographic characteristics, including age, sex, and comorbidities, further modulate side effect profiles through physiological changes and disease interactions. In older adults, age-related declines in renal and hepatic function, along with reduced physiological reserve, heighten susceptibility to side effects, particularly renal toxicity from drugs like nonsteroidal anti-inflammatory agents or aminoglycosides. Comorbidities exacerbate this risk; for example, patients with chronic kidney disease or heart failure are more prone to electrolyte imbalances or fluid retention from diuretics and antihypertensives. Sex differences also contribute, with women generally experiencing a higher incidence of adverse drug reactions due to pharmacokinetic variations, such as slower drug clearance and higher body fat distribution, which can prolong exposure to lipophilic compounds. These demographic influences highlight the need for dose adjustments and monitoring tailored to patient profiles. Lifestyle and environmental factors, such as diet, polypharmacy, and concurrent exposures, can amplify or mitigate side effects by affecting drug absorption, distribution, and interactions. Dietary components interact with medications; for instance, high-fat meals may delay gastric emptying and enhance bioavailability of lipophilic drugs like griseofulvin, potentially intensifying gastrointestinal side effects, while grapefruit juice inhibits CYP3A4 enzymes, elevating levels of statins and increasing myopathy risk. Polypharmacy, common in patients managing multiple conditions, heightens the potential for drug-drug interactions that precipitate side effects, such as serotonin syndrome from combined antidepressants or bleeding risks from concurrent anticoagulants and antiplatelets. Environmental factors like smoking can induce CYP1A2 activity, accelerating metabolism of theophylline and reducing its efficacy while altering side effect thresholds. Addressing these modifiable factors through lifestyle counseling can help optimize therapeutic outcomes and reduce adverse events.

Frequency and Assessment

Incidence and Prevalence

The incidence of side effects, often referred to as adverse drug reactions (ADRs) when unintended and harmful, varies significantly depending on the drug, patient population, and setting. In outpatient primary care settings, the pooled prevalence of ADRs is approximately 8.32%, with mild effects such as nausea or headache commonly reported in 10-20% of cases for frequently prescribed medications like antibiotics and analgesics.^[26]^[27] Recent studies indicate ADRs affect approximately 6-10% of hospitalized patients overall, with prevalence estimates around 6.2% (95% CI 5.1-7.2%) in a 2025 meta-analysis, and serious events varying from 3.5% to 10.1% depending on the region and methodology.^[28]^[29] Regulatory classifications further categorize side effect frequencies as very common (affecting more than 1 in 10 people), common (1 in 100 to 1 in 10), uncommon (1 in 1,000 to 1 in 100), rare (1 in 10,000 to 1 in 1,000), and very rare (fewer than 1 in 10,000), providing a standardized framework for assessing occurrence across treatments.^[27] Measurement of side effect incidence is influenced by differences between controlled clinical trials and real-world post-marketing surveillance. Clinical trials, involving selected populations under strict monitoring, primarily detect common ADRs occurring in more than 1% of participants, but they often underrepresent rare or long-term effects due to limited sample sizes and duration.^[30] In contrast, post-marketing data from spontaneous reporting systems reveal broader patterns but suffer from substantial underreporting, estimated at over 90% for all ADRs and up to 95% for serious ones, leading to incomplete prevalence estimates in everyday clinical practice.^[31] This underreporting is exacerbated by factors such as clinician time constraints and patient awareness gaps, resulting in lower documented rates in routine care compared to intensive study environments.^[32] Over the past decade (2015-2025), documentation of side effects has trended upward globally, driven by enhanced pharmacovigilance efforts, including mandatory reporting requirements and digital surveillance tools, with significant increases in ADR report submissions observed across multiple countries as of 2022. As of 2025, pharmacovigilance has seen further boosts from COVID-19 vaccine surveillance and AI-assisted signal detection.^[33]^[34] Reporting rates vary widely by country income level, with high-income countries often exceeding hundreds to over a thousand reports per million inhabitants annually (e.g., 1,130 in China in 2019), while low- and middle-income countries typically report far lower figures, often below 10 per million, reflecting disparities in healthcare infrastructure and regulatory enforcement.^[35]^[34] These variations underscore the role of improved international systems, such as the WHO's VigiBase, in bridging gaps and elevating overall awareness of side effect prevalence.^[36]

Reporting and Monitoring

Reporting and monitoring of side effects, particularly adverse drug reactions, occur primarily through post-approval pharmacovigilance systems designed to detect, assess, and mitigate risks after a medication reaches the market. These efforts involve both regulatory-mandated reporting mechanisms and clinical practices to ensure ongoing safety surveillance.^[37] In the United States, the Food and Drug Administration (FDA) operates the MedWatch program as the primary system for voluntary and mandatory reporting of adverse events associated with prescription drugs, over-the-counter medications, biologics, and medical devices. Healthcare professionals, patients, and consumers can submit reports via online forms, phone, or mail, detailing suspected side effects to facilitate FDA's analysis and potential regulatory actions such as label updates or product withdrawals. Mandatory reporting is required for manufacturers and healthcare providers in cases of serious events, while voluntary reports from the public help identify rare or emerging issues not captured in pre-approval trials.^[38]^[39] Similarly, in the European Union, the European Medicines Agency (EMA) manages EudraVigilance, a centralized database for collecting, managing, and analyzing reports of suspected adverse reactions to medicines authorized or under study in the region. Marketing authorization holders, clinical trial sponsors, and national competent authorities submit individual case safety reports electronically, enabling real-time signal detection and risk assessment across the EU. The system supports both individual case evaluations and aggregate data analysis to inform safety decisions, with public access to anonymized reports promoting transparency.^[40]^[41] Pharmacovigilance encompasses systematic processes for signal detection and causality assessment to evaluate reported side effects. Signal detection involves statistical and non-statistical methods to identify potential safety issues from disparate data sources like spontaneous reports and literature, using tools such as disproportionality analysis in databases like the FDA Adverse Event Reporting System (FAERS) or EudraVigilance. Once a signal is identified, causality assessment determines the likelihood that a drug caused the observed effect, often employing standardized scales like the Naranjo algorithm, a 10-question probabilistic tool scoring factors such as temporal association, dechallenge, and rechallenge to categorize reactions as definite, probable, possible, or doubtful. This algorithm, developed in 1981, aids in standardizing evaluations across reports to prioritize follow-up investigations.^[42]^[43]^[44] In clinical settings, ongoing monitoring of side effects integrates patient-reported data, laboratory evaluations, and digital health records to track individual responses during treatment. Patient diaries allow individuals to document symptoms, medication adherence, and perceived side effects in real-time, improving accuracy in capturing subjective experiences that might otherwise be underreported during visits. Routine lab tests, such as blood counts or liver function panels, detect objective indicators of toxicity, with thresholds triggering dose adjustments or discontinuation. Electronic health records (EHRs) facilitate integrated surveillance by aggregating patient data for automated alerts on potential adverse events, supporting pharmacovigilance through real-world evidence analysis while enhancing care coordination.^[45]

Examples and Case Studies

Common Examples in Medications

One of the most frequently encountered gastrointestinal side effects in medication use is nausea, commonly associated with opioids prescribed for pain management. For instance, opioids such as oxycodone and morphine often induce nausea in up to 25% of patients, particularly during initial treatment phases, contributing to discomfort that may lead to discontinuation of therapy.^[46]^[47]^[48] Similarly, nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, widely used for inflammation and pain relief, can cause nausea as a minor gastrointestinal disturbance, affecting a notable portion of users and often manifesting alongside dyspepsia.^[49]^[50] Neurological side effects, such as dizziness, are prevalent among antihypertensive medications, particularly beta-blockers like propranolol and metoprolol, which are staples in treating high blood pressure. These drugs frequently lead to dizziness or light-headedness due to their impact on blood pressure regulation, with studies indicating an increased risk (relative risk of 1.72) that affects daily activities like standing or driving for many patients.^[51]^[52]^[53] Dermatological reactions, including rashes, represent a common side effect of antibiotics, especially penicillin-based ones such as amoxicillin, used routinely for bacterial infections. Penicillin allergies or sensitivities often present as hives or maculopapular rashes in approximately 5-10% of treated individuals, prompting immediate medical attention to avoid escalation.^[54]^[55]^[56]

Historical and Notable Cases

One of the most infamous cases of drug-induced side effects is the thalidomide tragedy, which unfolded in the late 1950s and early 1960s. Developed by the German pharmaceutical company Chemie Grünenthal and marketed under names like Contergan, thalidomide was promoted as a safe sedative for treating morning sickness in pregnant women, with over 10,000 tons produced and distributed in 46 countries by 1961. However, by 1961, reports emerged linking the drug to severe congenital malformations, particularly phocomelia—a condition causing shortened or absent limbs—in newborns. An estimated 10,000 to 20,000 children worldwide were born with thalidomide-related birth defects between 1956 and 1962, with approximately 40% of affected infants dying in infancy. In the United States, the disaster was largely averted due to the vigilance of FDA reviewer Frances Kelsey, who rejected approval applications from 1960 to 1961 citing inadequate safety data on peripheral neuropathy and potential fetal risks, despite pressure from the distributor Richardson-Merrell; only 17 U.S. cases were reported from limited investigational use. The tragedy prompted global regulatory reforms, most notably the 1962 Kefauver-Harris Amendments in the U.S., which mandated proof of both safety and efficacy for new drugs, required informed consent in clinical trials, and strengthened FDA oversight of pharmaceutical advertising and testing protocols.^[57]^[58] Another landmark incident involved rofecoxib, marketed as Vioxx by Merck & Co., a selective cyclooxygenase-2 (COX-2) inhibitor approved by the FDA in May 1999 for osteoarthritis and acute pain relief, with over 80 million prescriptions filled in the U.S. alone by 2004. Initially hailed for reducing gastrointestinal side effects compared to traditional NSAIDs, Vioxx's cardiovascular risks became evident through post-marketing studies; the Adenomatous Polyp Prevention on Vioxx (APPROVe) trial, halted in September 2004, showed a doubled relative risk of serious cardiovascular events like myocardial infarction and stroke after 18 months of use (3.5% incidence in the Vioxx group versus 1.9% in placebo). Merck voluntarily withdrew Vioxx from the market on September 30, 2004, amid lawsuits estimating up to 27,000 heart attacks or strokes attributable to the drug, leading to settlements exceeding $4.85 billion. This event intensified scrutiny of the entire COX-2 inhibitor class, prompting FDA warnings for similar drugs like celecoxib (Celebrex) and valdecoxib (Bextra, withdrawn in 2005), and highlighting flaws in post-approval surveillance and direct-to-consumer marketing, which had generated over $2.5 billion in annual sales for Vioxx. The scandal spurred congressional investigations into FDA-Merck interactions and reinforced requirements for cardiovascular safety assessments in anti-inflammatory drug trials.^[59] The ongoing opioid crisis exemplifies long-term unintended consequences of pain management strategies, rooted in aggressive prescribing practices from the late 1990s onward. Opioids such as oxycodone (OxyContin, approved in 1995) and hydrocodone were promoted for chronic non-cancer pain based on assertions of low addiction risk—estimated at under 1% in some early claims—leading to a surge in prescriptions from 76 million in 1991 to 259 million by 2012 in the U.S. Addiction, recognized as a key side effect involving opioid use disorder (OUD), affects 8-12% of chronic pain patients on long-term therapy, with misuse rates up to 29%, driven by tolerance, dependence, and reward pathway alterations in the brain. This overprescription, influenced by pain advocacy campaigns like "pain as the fifth vital sign" in the 1990s and pharmaceutical marketing, contributed to over 500,000 overdose deaths from 1999 to 2020, predominantly from prescription and illicit opioids, with totals exceeding 645,000 opioid-involved deaths by 2021 and over 1.1 million total drug overdose deaths by 2023, marking a public health emergency declared by the U.S. Department of Health and Human Services in 2017. The crisis has reshaped pain management guidelines, with the CDC issuing restrictive prescribing recommendations in 2016 and 2022, emphasizing non-opioid alternatives and multimodal therapy to mitigate addiction risks, and ongoing efforts including expanded access to naloxone and treatment programs as of 2025.^[60]^[61]

References

[1]
Definition of side effect - NCI Dictionary of Cancer Terms
An effect of a drug or other type of treatment that is in addition to or beyond its desired effect. Side effects can be harmful or beneficial, ...
[2]
Finding and Learning about Side Effects (adverse reactions) - FDA
Aug 8, 2022 · Side effects, also known as adverse reactions, are unwanted undesirable effects that are possibly related to a drug. Side effects can vary from ...
[3]
Adverse Drug Reactions - StatPearls - NCBI Bookshelf
Jan 10, 2024 · A side effect is defined as a predictable or dose-dependent effect of a drug that is not the principal effect for which the drug was used.
[4]
Drug Reactions - MedlinePlus
Mar 16, 2023 · Side effects are unwanted, usually unpleasant, effects caused by medicines. Most are mild, such as a stomachache, dry mouth, or drowsiness, and ...
[5]
What are side effects? - PMC - NIH
Mar 11, 2023 · The WHO defines a side effect as any unintended effect occurring at a normal dose related to pharmacological properties. The WHO definition ...
[6]
Medication Side Effects | Department of Human Services
What might cause medication side effects? · Interactions with other drugs · Interactions with over-the-counter drugs · Interactions with food · Interactions with " ...
[7]
Medication Safety and Your Health - CDC
Nov 18, 2024 · An adverse drug event (ADE) is when a medication causes harm to someone. ADEs include allergic reactions, side effects, overmedication and ...
[8]
Medication side effects: What are your options? - Harvard Health
Nov 20, 2024 · All medicines have potential side effects. Usually, side effects are more bothersome than serious –– though a few are dangerous.
[9]
Finding better ways to reduce serious drug side effects
Aug 9, 2017 · Predicting potential side effects is a complicated task. Even after extensive testing, some adverse effects often don't show up until drugs are ...Missing: definition | Show results with:definition
[10]
Medications | VA Birmingham Health Care | Veterans Affairs
Oct 13, 2022 · A side effect is an expected and known secondary effect of a medication. The side effect is typically not the primary reason the drug was chosen ...<|control11|><|separator|>
[11]
Side-effect - Origin & Meaning of the Phrase
From 1884, "side effect" combines side (adj.) + effect (n.), meaning a subsidiary consequence of an action, especially in medicine since 1939.Missing: pharmacology | Show results with:pharmacology
[12]
[PDF] Definitions and Standards for Expedited Reporting - FDA
Mar 1, 1995 · The old term "side effect" has been used in various ways in the past, usually to describe negative (unfavorable) effects, but also positive ...
[13]
Minoxidil - StatPearls - NCBI Bookshelf
Feb 24, 2023 · Minoxidil exerts its antihypertensive effect by opening adenosine triphosphate (ATP)-sensitive potassium channels, thereby reducing peripheral ...
[14]
How minoxidil was transformed from an antihypertensive to hair-loss ...
Jul 20, 2011 · Once minoxidil was on the market for hypertension, it quickly became an open secret that the drug stimulated hair growth.
[15]
Immunosuppressants: Definition, Uses & Side Effects
Healthcare providers prescribe immunosuppressants to treat certain autoimmune diseases and prevent organ or stem cell transplant rejection. These ...
[16]
Benefit-Risk Assessment for New Drug and Biological Products - FDA
Apr 4, 2024 · The intent of this guidance is to clarify for drug sponsors and other stakeholders how considerations about a drug's benefits, risks, and risk ...
[17]
Evaluating Drug Efficacy and Safety - Clinical Pharmacology
The commonly used term side effect is imprecise, often used to refer to the unintended effects of a medication that occur within the medication's therapeutic ...Missing: origin | Show results with:origin
[18]
Side Effect - Canadian Society of Pharmacology and Therapeutics
This term was first used in the modern concept in 1814. A side effect is a predictable type of Adverse Drug Reaction, notably for off-target effects which can ...Missing: origin | Show results with:origin
[19]
Minoxidil: Formulation, Dosage & Side-Effects - ISHRS
During clinical trials in the 1970s, researchers discovered that one of its side effects was excessive hair growth, known as hypertrichosis. This unexpected ...
[20]
A history of aspirin - The Pharmaceutical Journal
Sep 26, 2014 · c400 BC: In Greece, Hippocrates administers willow leaf tea, which contains the natural compound from which aspirin is derived, to women to ease ...
[21]
Aspirin: Turn-of-the-Century Miracle Drug | Science History Institute
Jun 3, 2009 · The first recorded use of salicylates dates back about 4,000 years to the Sumerians, who noted the pain remedies of the willow tree on early ...
[22]
Drug Repurposing: An Effective Tool in Modern Drug Discovery - NIH
Feb 21, 2023 · Drug repurposing is the technique of using an existing drug or drug candidate for a new treatment or medical condition for which it was not indicated before.
[23]
Therapeutic innovation in drug repurposing: Challenges and ...
Minoxidil is a clear example of how a drug designed for one route of administration and indication can be effectively repurposed by altering its delivery ...
[24]
Prevalence of adverse drug reactions in the primary care setting
May 26, 2021 · The pooled prevalence of ADRs in the primary care setting was 8.32% (95% CI, 7.82, 8.83). The percentage of preventable ADRs ranged from 12.35–37.96%.<|separator|>
[25]
How often do side effects occur, from very common to rare?
The chance of having a drug side effect generally falls in these ranges: Very common: affecting more than 1 in 10 people (>10%); Common: affecting between 1 ...
[26]
Preventable Adverse Drug Reactions: A Focus on Drug Interactions
Mar 6, 2018 · After discussing this case, we will discuss the prevalence and incidence of adverse drug reactions. We will then examine several well ...
[27]
Difficulties in assessing adverse drug reactions in clinical trials
Therefore only the most common acute, dose-related ADRs are usually detected in the pre-marketing phase. 2. The detection and assessment of ADRs in clinical ...Missing: incidence | Show results with:incidence
[28]
Underreporting of Adverse Drug Events: a Look into the Extent ...
Underreporting of ADEs refers to the failure or incomplete reporting of incidents where patients experience harmful reactions from medications by healthcare ...
[29]
Factors Associated with Underreporting of Adverse Drug Reactions ...
Jun 6, 2023 · Underreporting is the major limitation of the voluntary reporting system of adverse drug reactions (ADRs). Our 2009 systematic review showed the ...
[30]
Trends of reporting of 'serious'vs. 'non-serious' adverse drug ... - NIH
ADR reports mainly concern NSADRs during first years of marketing. Reports of SADRs are proportionally more frequent later. Keywords: 'serious' adverse drug ...
[31]
Global patterns of adverse drug reactions over a decade - PubMed
Dec 1, 2012 · High-income countries had the highest ADR reporting rates (range 3-613 reports/million inhabitants/year) and low-income countries the lowest ( ...
[32]
Global Patterns of Adverse Drug Reactions Over a Decade
It was showed that high- Income countries had the highest ADR reporting rates and low-income countries the lowest, with large variations across countries in ...<|control11|><|separator|>
[33]
Good Pharmacovigilance Practices and Pharmacoepidemiologic ...
Aug 24, 2018 · This document provides guidance to industry on good pharmacovigilance practices and pharmacoepidemiologic assessment of observational data regarding drugs.
[34]
The FDA Safety Information and Adverse Event Reporting Program
MedWatch is made up of voluntary and mandatory reporting on prescription medicines, over-the-counter medicines, non-vaccine biologicals, medical devices, ...Reporting Serious Problems to ...FDA's MedWatchFDA MedWatch/Safety AlertsMedical Product Safety ...About the MedWatch E-list
[35]
MedWatch Forms for FDA Safety Reporting
Oct 22, 2025 · Safety reporting portal for health professionals, patients, consumers and industry. Find pdf fillable forms in English and Spanish and a ...
[36]
EudraVigilance | European Medicines Agency (EMA)
EudraVigilance is the system for managing and analysing information on suspected adverse reactions to medicines which have been authorised or being studied ...Electronic reporting · EudraVigilance system overview · EudraVigilance training
[37]
EudraVigilance system overview | European Medicines Agency (EMA)
EudraVigilance is a system for monitoring the safety of medicines. Its components facilitate electronic reporting of suspected adverse reactions related to ...
[38]
Signal management | European Medicines Agency (EMA)
Safety signals can be detected from a wide range of sources, such as spontaneous reports, clinical studies and scientific literature. The EudraVigilance ...
[39]
[PDF] Practical Aspects of Signal Detection in Pharmacovigilance - CIOMS
... signal detection methods in the EudraVigilance Data Analysis System (9). The FDA Guidance on Good Pharmacovigilance Practices and Pharmacoepi- demiology ...
[40]
A method for estimating the probability of adverse drug reactions
A method for estimating the probability of adverse drug reactions - Naranjo - 1981 - Clinical Pharmacology & Therapeutics - Wiley Online Library.
[41]
[PDF] Real-World Data: Assessing Electronic Health Records and Medical ...
This guidance represents the current thinking of the Food and Drug Administration (FDA or Agency) on this topic. It does not establish any rights for any ...
[42]
Prescription Opioids DrugFacts | National Institute on Drug Abuse
Jun 1, 2021 · However, opioids can also have harmful effects, including: drowsiness; confusion; nausea; constipation; euphoria; slowed breathing. Opioid ...
[43]
New Safety Measures Announced for Opioid Analgesics ... - FDA
Aug 31, 2016 · Common side effects include drowsiness, dizziness, nausea, vomiting, constipation, and slowed or difficult breathing. Opioids also carry ...
[44]
Management of common opioid-induced adverse effects - PubMed
Oct 15, 2006 · Nausea occurs in approximately 25 percent of patients; prophylactic measures may not be required. Patients who do develop nausea will require ...
[45]
Gastrointestinal and Cardiovascular Risk of Nonsteroidal Anti ...
The use of NSAIDs is associated with various gastrointestinal side effects. Minor side effects such as nausea, dyspepsia, anorexia, abdominal pain ...<|separator|>
[46]
Non-steroidal anti-inflammatory drugs and the gastrointestinal tract
A third of patients consuming NSAIDs develop foregut symptoms of dyspepsia (epigastric discomfort, bloating, post-prandial nausea, early satiety and belching) ...
[47]
Beta blockers - Mayo Clinic
Side effects. Common side effects of beta blockers can include: Cold hands or feet. Extreme tiredness. Weight gain. Dizziness or light-headedness. Less ...
[48]
Beta Blockers - StatPearls - NCBI Bookshelf
Bradycardia and hypotension are two adverse effects that may commonly occur. Fatigue, dizziness, nausea, and constipation are also widely reported.
[49]
β‐Blockers and risk of neuropsychiatric disorders - PubMed Central
Dec 10, 2024 · Our analysis revealed that β‐blocker use was significantly associated with an increased risk of dizziness (RR 1.72, 95% CI [1.39–2.14]; I 2 = 1% ...
[50]
Penicillin allergy - Symptoms & causes - Mayo Clinic
Sep 20, 2025 · Penicillin is used to treat bacterial infections. Penicillin allergy may cause hives, rash and itching.Overview · Symptoms · When to see a doctor · Causes
[51]
Penicillin - StatPearls - NCBI Bookshelf - NIH
Penicillin V and G can have adverse effects, including nausea, vomiting, diarrhea, rash, abdominal pain, and urticaria. In addition, Penicillin G can have other ...Penicillin · Indications · Adverse Effects
[52]
Penicillin Allergy - StatPearls - NCBI Bookshelf
Common cutaneous symptoms are generalized urticaria, flushing, pruritis, and angioedema. Go to: Evaluation. To determine if a patient has an IgE mediated ...Bookshelf · Penicillin Allergy · Epidemiology<|control11|><|separator|>
[53]
How the thalidomide scandal led to safer drugs - MedicalNewsToday
Dec 15, 2020 · The thalidomide tragedy demonstrated the need for strictly enforced regulation of drug testing, marketing, dispensing, and use.
[54]
How a courageous physician-scientist saved the U.S. from a birth ...
Mar 10, 2020 · As an FDA reviewer in 1961, Frances Kelsey, MD, PhD, resisted pressure to approve the drug thalidomide, later shown to cause severe birth ...Missing: stricter | Show results with:stricter<|separator|>
[55]
Failing the Public Health — Rofecoxib, Merck, and the FDA
The message that was duly reinforced was that rofecoxib had no cardiovascular toxicity: rather, naproxen was cardioprotective. Only by happenstance, in a trial ...
[56]
Pain Management and the Opioid Epidemic - NCBI Bookshelf - NIH
For example, nausea, constipation, sedation, and other side effects are common after the administration of opioids in patients with cancer pain, just as they ...