Nearly every drug sold without a prescription can cause serious harm or death if enough is taken, but a handful of common over-the-counter (OTC) medications account for the vast majority of dangerous overdoses. Acetaminophen, ibuprofen, aspirin, diphenhydramine, dextromethorphan, loperamide, and even some supplements and antacids all carry real overdose risk. The fact that these products sit on open shelves and require no doctor visit creates a false sense of safety that the medical literature does not support.
Acetaminophen Is the Single Most Dangerous OTC Drug in Overdose
Acetaminophen (sold as Tylenol and found in dozens of cold, flu, and pain combination products) is consistently the OTC medication most frequently involved in overdose-related liver failure and death. At normal doses, a small fraction of the drug gets converted into a reactive byproduct that the liver neutralizes with a protective molecule called glutathione. In overdose, the liver’s glutathione supply runs out, and that reactive byproduct starts destroying liver cells directly.1PubMed Central. Acetaminophen Hepatotoxicity The damage can progress silently for a day or more before symptoms appear, which is part of what makes acetaminophen overdose so treacherous. By the time someone feels truly sick, their liver may already be in crisis.
One of the biggest risks with acetaminophen is unintentional overdose from stacking products. Many cold and flu remedies, sleep aids, and prescription painkillers contain acetaminophen alongside other active ingredients, and people often don’t realize they’re doubling up. In one study, about 46% of adults demonstrated they would overdose by taking two acetaminophen-containing products simultaneously.2PubMed Central. Risk of unintentional overdose with non-prescription acetaminophen products The combination of acetaminophen with opioid-containing products has been a particular driver of liver injury; analysis of U.S. poison control data found that acetaminophen-opioid combinations were overrepresented among cases with hepatic injury, while combination with cough and cold products alone was less likely to cause serious harm.3PubMed. Trends in hepatic injury associated with unintentional overdose of paracetamol (Acetaminophen) in products with and without opioid
If acetaminophen overdose is caught early, a well-established antidote exists: acetylcysteine (often called NAC), which replenishes the liver’s glutathione stores. But “early” is the operative word. Delays of even several hours sharply reduce the antidote’s effectiveness, and in severe cases liver transplant becomes the only option.
Ibuprofen and Aspirin
Ibuprofen and other nonsteroidal anti-inflammatory drugs (NSAIDs) are the second most commonly ingested OTC medications in overdose situations. While NSAID overdose is generally less immediately lethal than acetaminophen overdose, it can still cause serious organ damage. The kidneys are the primary concern: medical literature has linked NSAID use to acute kidney injury, chronic kidney disease, and inflammatory kidney conditions.4PubMed Central. Kidney damage from nonsteroidal anti-inflammatory drugs-Myth or truth? Review of selected literature In large overdoses, acute kidney failure has been documented even in otherwise healthy individuals, including a case of a two-year-old who developed reversible kidney failure after ingesting roughly 640 mg per kilogram of body weight.5PubMed. Acute renal insufficiency in ibuprofen overdose Gastrointestinal bleeding and metabolic acidosis are additional risks at high doses.
Aspirin (a salicylate) is a different kind of beast. In overdose, salicylates disrupt several fundamental metabolic processes at once. They overstimulate the brain’s breathing center, cause the body to burn through glucose and oxygen at an accelerated rate, and interfere with the normal energy-production cycle in cells. The result is a cascade of problems including dangerous acid-base imbalances in the blood, dehydration, electrolyte depletion, and elevated body temperature.6Pediatrics. Pathophysiology of Aspirin Overdosage Toxicity, With Implications for Management Severe aspirin poisoning can be fatal, and because the drug is absorbed slowly from the stomach, blood levels can continue to rise for hours after ingestion, making timing of treatment critical.
Antihistamines, Especially Diphenhydramine
Diphenhydramine (Benadryl) is the OTC antihistamine most commonly involved in overdose deaths. It is found everywhere: in allergy pills, sleep aids, cold remedies, and motion-sickness tablets. Between 2019 and 2020, antihistamines were found in 15% of all U.S. drug overdose deaths, with about 3.6% of overdose deaths involving antihistamines alone, and diphenhydramine was the most commonly identified antihistamine in those fatalities.7PubMed Central. Treating Diphenhydramine Overdose: A Literature Review of Currently Available Treatment Methods There is no specific antidote for diphenhydramine poisoning, making treatment largely supportive and the stakes of overdose correspondingly higher.
In overdose, diphenhydramine causes a distinctive and dangerous combination of effects: agitation, hallucinations, seizures, dangerously abnormal heart rhythms, and in severe cases, coma and cardiac arrest. Viral social media “challenges” have periodically encouraged young people to take large doses, which has amplified the problem.
Newer antihistamines like cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra) are dramatically safer in overdose. A detailed review of these second-generation antihistamines found an excellent cardiac safety profile with no evidence of heart toxicity even at four times the standard dose, provided the person has no preexisting heart-rhythm disorders or relevant electrolyte imbalances.8PubMed. Cardiac safety of second-generation H(1)-antihistamines when updosed in chronic spontaneous urticaria In children who accidentally ingest large amounts of newer antihistamines, the situation can typically be managed at home without an emergency department visit.9PubMed. Safety of antihistamines in children The difference in safety margin between older and newer antihistamines is enormous and worth knowing if you keep allergy medications around the house.
Cough Suppressants and Decongestants
Dextromethorphan (DXM), the cough suppressant found in products like Robitussin and NyQuil, is widely abused for its dissociative and hallucinogenic effects at high doses. In overdose it can cause seizures, loss of consciousness, and serotonin syndrome, a potentially fatal condition involving dangerous spikes in body temperature, muscle rigidity, and altered mental status. Serotonin syndrome is especially likely when DXM is combined with other serotonin-affecting drugs such as antidepressants.10Brain and Development Case Reports. Seizure and coma with overdose dextromethorphan: A case report
Decongestants present a different risk profile depending on the type. Oral pseudoephedrine raises blood pressure and heart rate in a dose-dependent way, with higher doses and immediate-release formulations producing larger spikes. A meta-analysis found that even standard doses caused a small but measurable increase in systolic blood pressure and heart rate.11PubMed. Effect of oral pseudoephedrine on blood pressure and heart rate: a meta-analysis In overdose or in someone with uncontrolled high blood pressure, the cardiovascular effects can become dangerous.
Nasal spray decongestants containing oxymetazoline (Afrin) or similar imidazoline compounds pose a less obvious but very real threat, particularly to young children. Oxymetazoline is a potent stimulant of certain receptors in the nervous system, and in overdoses as small as one to two milliliters, it can cause a slowed heartbeat and suppressed breathing.12PubMed. Not Just a Drop in the Bucket-Inversion of Oxymetazoline Nasal Decongestant Container Increases Potential for Severe Pediatric Poisoning Toxicity from imidazoline-containing nasal and eye-drop products has been documented from both oral ingestion and excessive topical application in children.13PubMed. Pediatric poisoning from over-the-counter imidazoline-containing products
Loperamide and the Opioid Connection
Loperamide (Imodium) is an anti-diarrheal drug that works on opioid receptors in the gut. At normal doses, it stays in the intestine and doesn’t reach the brain. But at massively elevated doses, loperamide crosses the blood-brain barrier and produces opioid-like effects, which is why some people misuse it as a substitute when other opioids are unavailable.14PubMed Central. Cardiac Arrhythmia Secondary to Loperamide Abuse and Toxicity
The heart is the organ most at risk. At high doses, loperamide blocks ion channels in cardiac tissue, disrupting the electrical signals that coordinate heartbeats. Case reports of life-threatening heart arrhythmias in people who have overdosed on loperamide have become increasingly common in the medical literature.15PubMed Central. Loperamide-Induced Cardiac Events: Case Reports and Review The cardiac toxicity can be prolonged because loperamide has a long half-life and accumulates in the body, meaning heart-rhythm problems may persist well after the person stops taking it.16PubMed Central. Loperamide overdose causing torsades de pointes and requiring Impella temporary mechanical support: a case report In response to rising reports of abuse, the U.S. FDA has required packaging changes and dose limits for loperamide products.
Supplements, Antacids, and Laxatives
Products that most people would never think of as “drugs” can also cause dangerous overdoses. Iron supplements are a classic example. Excess iron overwhelms the body’s storage systems and generates reactive oxygen species that damage cells throughout the gastrointestinal tract, liver, heart, kidneys, and blood-forming tissues.17PubMed. Iron; Benefits or threatens (with emphasis on mechanism and treatment of its poisoning) Iron poisoning in children used to be a leading cause of pediatric poisoning death before child-resistant packaging became standard.
Calcium carbonate antacids (Tums) seem utterly benign, but chronic overuse or a single large binge can cause a dangerous spike in blood calcium levels. Case reports describe hypercalcemic crisis from excessive calcium carbonate ingestion, a condition that can affect the heart, kidneys, and brain.18PubMed Central. Calcium Carbonate (Tums)-Associated Hypercalcemic Crisis
Magnesium-containing laxatives and bowel prep solutions carry a risk that catches many clinicians off guard. In one fatal case, a woman with chronic constipation who regularly used magnesium laxatives developed lethal hypermagnesemia despite having normal kidney function; her retained stool apparently acted as a reservoir, continuously releasing magnesium into her bloodstream.19PubMed. Fatal Hypermagnesemia Due to Laxative Use In another case, a patient who ingested magnesium citrate for preoperative bowel preparation developed severe shock, required mechanical ventilation, and was found to have magnesium blood levels more than four times the normal upper limit.20PubMed Central. Induction of potentially lethal hypermagnesemia, ischemic colitis, and toxic megacolon by a preoperative mechanical bowel preparation: report of a case
Herbal and dietary supplements sit in a regulatory gray zone. They are not held to the same safety and labeling standards as pharmaceuticals, which means dosing can be inconsistent and contaminants are possible. Green tea extract is one of the better-studied examples: liver injury typically shows up within one to three months of starting a green tea extract supplement, and up to 10% of patients who develop jaundice from it have died.21PubMed Central. Liver Injury from Herbal and Dietary Supplements – Section: HDS Commonly Associated with Liver Injury Toxicity risk rises when supplements are used for non-traditional purposes, at excessive doses, for prolonged periods, or alongside multiple other medications.22PubMed Central. Dietary supplements and herbal medicine toxicities-when to anticipate them and how to manage them
Who Is Most at Risk
Children under six make up a disproportionate share of OTC overdose emergency visits, almost always from unsupervised ingestion. An estimated 6,400 emergency department visits per year in the U.S. result from young children getting into liquid OTC medications, with nearly two-thirds of those visits involving kids aged two and under. Liquid acetaminophen and liquid diphenhydramine were the most commonly implicated, with emergency visit rates per bottle sold comparable to high-risk prescription medications like clonidine.23PubMed Central. Ingestion of Over-the-Counter Liquid Medications Emergency Department Visits by Children Aged Less Than 6 Years, 2012-2015 Most of these ingestions happen in the child’s home, and in over half the cases the child was actually the intended recipient of the medicine, suggesting that familiarity with the product may lower a caregiver’s guard.24PubMed. New insights into root causes of pediatric accidental unsupervised ingestions of over-the-counter medications
Adolescents represent a very different overdose profile. In intentional-suspected-suicide calls to U.S. poison centers over a decade, acetaminophen was the single most commonly ingested substance (about 11% of cases), followed by ibuprofen (9%) and antihistamines (5%).25PubMed. Adolescent Suicidal Ingestion: National Trends Over a Decade The rate of intentional acetaminophen overdose among young people aged 10 to 24 rose by about 9% between 2007 and 2018, with the steepest increases among young women.26PubMed. Paracetamol-related intentional drug overdose among young people: a national registry study of characteristics, incidence and trends, 2007-2018 The easy availability of these drugs in the home is widely considered a contributing factor.
Older adults face a quieter but persistent risk. Kidney function declines with age, and many elderly people have some degree of chronic kidney disease without knowing it. When those individuals take nephrotoxic OTC drugs like NSAIDs, their risk of adverse drug reactions, hospitalization, and extended hospital stays increases.27PubMed Central. Renally Inappropriate Medications in the Old Population: Prevalence, Risk Factors, Adverse Outcomes, and Potential Interventions The combination of impaired kidney function with degenerative vascular disease or heart failure, both common in the elderly, substantially raises the risk of drug-induced kidney damage.28PubMed. Drugs and the kidney in the elderly This doesn’t require a dramatic overdose; chronic use at the upper end of recommended doses may be enough to cause trouble in someone whose kidneys are already compromised.
What Packaging Restrictions Have Actually Accomplished
The United Kingdom’s 1998 legislation restricting acetaminophen and aspirin pack sizes is the most studied harm-reduction experiment for OTC overdose. The law limited purchases to 16 tablets from non-pharmacy stores and 32 from pharmacies, based on the reasoning that even a small barrier might interrupt impulsive overdose attempts. The results were meaningful. Annual deaths from acetaminophen poisoning dropped by about 21%, deaths from salicylate poisoning dropped by roughly 48%, and liver transplants following acetaminophen overdose fell by about two-thirds.29BMJ. Effects of legislation restricting pack sizes of paracetamol and salicylate on self poisoning in the United Kingdom: before and after study A broader assessment confirmed a substantial decrease in the occurrence and severity of acetaminophen overdose cases following the regulations.30The Lancet. Reducing paracetamol overdoses
The evidence isn’t entirely clean. A systematic review noted that while one study found reduced mortality in England and Wales after one year, another found no difference in Scotland two years later, and the studies generally had short follow-up periods and methodological limitations.31Journal of Public Health. Restricting paracetamol in the United Kingdom to reduce poisoning: a systematic review Still, the overall direction of the evidence is positive and has influenced policy discussions in other countries. The United States has never imposed comparable pack-size limits, though the FDA has taken other steps like requiring clearer labeling and limiting the amount of acetaminophen in prescription combination drugs.
When Treatment Options Are Limited
A common assumption is that hospitals can simply “pump the stomach” or give an antidote for any overdose. The reality is far more constrained. Of the dozens of antidotes that exist, only a few are regularly used in clinical practice, including activated charcoal, acetylcysteine (for acetaminophen), naloxone (for opioids), and sodium bicarbonate. Even these are used in a minority of poisoning cases, and there is little randomized trial evidence supporting most antidotes.32PubMed Central. Who gets antidotes? choosing the chosen few
For many OTC overdoses, treatment is purely supportive: IV fluids, monitoring heart rhythm, managing seizures if they occur, and waiting for the body to clear the drug. Diphenhydramine has no antidote. Loperamide’s cardiac effects can require mechanical cardiac support in extreme cases. Aspirin overdose may need aggressive correction of blood pH and electrolytes. The takeaway is that the safety net after an OTC overdose is thinner than most people assume, which makes prevention and awareness of dose limits substantially more important than relying on emergency medicine to clean up afterward.