What is a drug overdose?

Quick Answer
An overdose involves an acute ingestion of an excessive amount of a drug beyond the recommended quantity. Overdoses may be intentional or accidental and are especially likely when the substance content of a drug is unknown, when a drug is "cut" with another drug or substance, or when multiple drugs are taken together or are mixed with alcohol. Overdoses are common with drugs of abuse, such as heroin, opioids, and barbiturates. Though overdoses can be fatal, they are also preventable. An overdose involves an acute ingestion of an excessive amount of a drug beyond the recommended quantity. Overdoses may be intentional or accidental and are especially likely when the substance content of a drug is unknown or when multiple drugs are taken together. Overdoses are common with drugs of abuse, such as heroin, opioids, and barbiturates. Though overdoses can be fatal, they are also preventable.
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Overdoses result from taking too much of a dangerous substance, whether an illicit substance of abuse or medications (such as prescriptions and over-the-counter drugs ) approved by the US Food and Drug Administration (USDA). For example, accidental overdose can occur when a person mistakenly ingests a repeated or double dose of a prescription. Excessive drug ingestion can occur with a single drug or with a combination of drugs that have overlapping effects.

Fatal overdoses primarily involve dangerous drug mixtures, such as concomitant alcohol and benzodiazepine use or a mixture of heroin and benzodiazepine. Combinations of alcohol with street drugs appear to be the most deadly.

The amount of a drug needed to cause an overdose varies by person, by type of drug, and by substance purity or potency. For example, increased potency of heroin products in the early twenty-first century compared with their historical content resulted in greater rates of heroin-associated fatal overdose.

Prescription-associated overdoses most often involve sedatives or painkillers, such as hydrocodone, methadone, oxycodone, and oxymorphone. In 2013, there were twenty-seven thousand accidental overdoses in the United States. Prescription drug abuse is a growing cause of fatal overdoses, particularly as a result of opioid misuse. According to the Centers for Disease Control and Prevention (CDC), overdose deaths increased from 1999 to 2004 because of painkillers, cocaine, and sedatives, and not because of heroin or methamphetamine. By June 2015, overdose deaths became the number one cause of death from injury in the United States. The number of deaths caused by overdose more than doubled between 2000 and 2014 , with half of those deaths related to prescription drugs.

The National Institute on Drug Abuse reported in February 2015 a study from the National Center for Health Statistics at the Centers for Disease Control and Prevention (CDC) that from 2001 to 2013, the number of deaths caused by an overdose of prescription drugs increased 2.5 times, from just under 10,000 deaths to approximately 23,000 deaths; deaths caused by an overdose of prescription opioid pain relievers increased 3 times, from under 6,000 to over 17,000; deaths caused by an overdose of heroin increased 5 times in that same time period, from approximately 1,700 in 2001 to over 8,000 in 2013.

Risk Factors

The populations at greatest risk for overdose are illicit drug users, youth, and elderly prescription-drug users. The risk of overdose increases when multiple drugs are prescribed or when illicit drugs are mixed with each other drugs or with alcohol. In addition, risks increase in recovering drug users who regress, traditionally called relapsing. Many who regress and use their previous drug of choice often use the same level of the drug they did when deep in their addiction. After a period of sobriety, however, their tolerance is much lower and the result of an unintentional fatal overdose.

Long-term illicit drug users tend to overdose because their tolerance for the drug has increased and they become overconfident; many times they use drugs alone, which presents added danger and risk. Taking drugs by inhalation or injection is also more likely to result in toxicity because drug concentrations reach the brain more rapidly.

Painkiller overdose is associated with risk populations distinct from those of illicit drug use. Prescription misuse and overdose most commonly develop in middle-aged persons and with people living in poverty or in rural areas. Long-term prescription opioid users or people who receive painkiller prescriptions from multiple prescribers are more likely to receive unsafe drug quantities and to ingest toxic dosages. People with existing mental health problems, such as depression or anxiety, also experience greater rates of overdose with prescription or illicit drugs.


Side effects of overdoses are often particular to the type of drug ingested, although some signs of overdose are consistent with general toxicity. Common symptoms of overdose include nausea and vomiting, prolonged sleep or lack of consciousness whereby the individual is impossible to rouse, snoring and gurgling, blue lips, and blue nails. Additional symptoms relate to sedative or stimulatory effects on nervous system and organ functions. These symptoms include abnormal breathing, slurred speech, poor coordination, slow or fast pulse, high or low body temperature, large or small pupil size, flushing and perspiration, nonresponsive sleep, violent outbursts, and delusions or hallucinations.

Typically, overdose symptoms mimic and extend the clinical effect of the drug, whether the drug is sedating or stimulatory. For example, such stimulants as cocaine can cause seizures and heart arrhythmias, whereas sedating benzodiazepines or opioids can induce coma. However, paradoxical effects are possible, and toxic amounts of both sedatives and stimulants impair crucial breathing functions.

Screening and Diagnosis

Identification of people at risk for substance abuse or prescription misuse is critical to screening for potential overdose. These users have lower inhibitions about drug dosing, blunted emotional responses and impulse control to guide appropriate drug use, and lower likelihood of having social contacts that discourage inappropriate drug use. Although identification of a substance abuse problem does not guarantee an ingestion of toxic dosages, it does lead to active monitoring of a risk group.

Polydrug use is a large overdose risk factor that can be identified in a screening of patient-specific prescription habits or pharmacy refill rates. Alcohol is the most frequent substance identified in combination overdoses, so screening for levels of alcohol use before prescribing high-risk medications is another useful way to identify overdose likelihood.

Recognition and diagnosis of an overdose in the emergency room setting should be done quickly for appropriate care. Considerations include consciousness, shallow breathing, and slurred speech as traditional signs of substance abuse. Blood tests should be performed to screen for substances in the system so that the appropriate treatment can be employed to counteract damaging symptoms. Diagnosis of a drug overdose is particularly challenging when the patient is unconscious and the substances remain unknown.

In a community setting, early signs that can indicate an increased risk for potential drug overdoses include frequent morning hangovers from alcohol abuse, red streaks in the whites of the eyes, purchase of large drug quantities, appetite changes, and new sleep patterns. Extreme behavior changes, such as hostility, depression and mood swings, secretive actions, confusion, and social isolation, likewise represent uncontrolled drug use that can lead to overdose.

Treatment and Therapy

Effective treatment hinges on early recognition of the overdose. In the recent past, treatment was often administered in an emergency room setting. More and more first responders, such as EMTs and police, are now trained in administering and carry Naloxone (also called Narcan). Naloxone is a synthetic opioid antagonist that is used as an antidote for opioid overdose. It reverses the life-threatening respiratory depression caused by natural and synthetic opioids, including heroin, morphine, oxycontin, propoxyphene, and methadone. Naloxone is not a controlled substance and was once only available by prescription. Beginning in 2014 and in response to the growing opiate epidemic in the United States, however, pharmacies across the country also began carrying the drug for sale over-the-counter.

Care after an actual or suspected overdose begins with basic functions: If Naloxone or Narcan is available, it should be administered immediately. Emergency personnel must be called regardless, because even if Naloxone/Narcan is used and the overdosing individual appears to recover, it is quite possible that they will regress into an overdose state again because the half-life of Naloxone/Narcan is much shorter than opiates. If Naloxone is not available and after 911 has been called, any airway barriers in the overdosing individual must be cleared and oxygen levels should be restored by using mouth-to-mouth resuscitation and/or CPR. Once in a hospital setting, intravenous fluids are often provided to assist with electrolyte balance; monitoring of vital organs, such as the cardiac and pulmonary systems, confirms stability and treatment response and can aid in diagnosing what drugs were involved.

As an overdosed patient achieves stable heart and lung function, considerations begin for substance removal. Gastric lavage and activated charcoal remove excessive medication from the stomach through the esophagus or through binding within the stomach, respectively. However, these methods are not recommended for every substance, and they do not fully remove drugs, which are already circulating in the blood. In some circumstances, hemodialysis can be used to filter substances from the blood and to prevent kidney damage. Infrequently, antidotes to specific substances cause rapid resolution of overdose symptoms. For example, the benzodiazepine antagonist flumazenil blocks toxic amounts of benzodiazepine at their receptors to counteract overdose symptoms.

To supplement emergency treatment, psychological needs must be evaluated, especially for cases of intentional overdose and in patients who suffer from substance use disorder. Mental health counseling or behavioral care should be implemented as part of a holistic approach to treatment of substance use disorder.


The CDC encourages state and federal tracking of overdose trends and increased education about these trends to improve substance abuse and overdose prevention efforts. Public health strategies emphasize avoidance of prescription drug sharing and awareness of available prescription-medication disposal programs. The Office of National Drug Control Policy enforces initiatives to restrict illicit drug use through education, drug tracking, and law enforcement options.

Known illicit drug users should be advised about the greater risks of overdose during withdrawal or relapse periods after tolerance diminishes. Prevention of accidental overdose in particular hinges on counseling and communication. Family members and loved ones of opiate addicts should be trained in the use of Naloxone/Narcan and carry it with them at all times. While Naloxone cannot prevent an overdose or by itself cause an addicted individual to recover, it prevents death and provides the opportunity for the individual to choose recovery and then get additional help.

Overdose of prescription medications has the most potential for prevention success. Limiting access to the highest-risk drugs, providing proactive mental health care, reducing insurance coverage of multiple painkillers, and increasing health professional awareness and education all support lower rates of overdose in the general population. Trained health professionals can identify at-risk patients, such as those with multiple prescriptions, before an overdose occurs. With increased prescription drug monitoring and pain clinic oversight, professionals and patients can minimize the occurrences of prescription drug overdose.


"Opioid Addiction Disease: 2015 Facts and Figures." ASAM. American Society of Addiction Medicine, 2015. Web. 29 Oct. 2015. PDF file.

"Overdose Death Rate." DrugAbuse.gov. National Institute on Drug Abuse, Feb. 2015. Web. 29 Oct. 2015.

Paulozzi, Leonard, et al. “CDC Grand Rounds: Prescription Drug Overdoses—A US Epidemic.” MMWR Weekly 61.1 (2012): 10–13. Print.

Pollack, Harold. "100 Americans Die of Drug Overdoses Each Day. How Do We Stop that?" Washington Post. Washington Post, 7 Feb. 2014. Web. 29 Oct. 2015.

Shannon, Michael W., Stephen W. Borron, and Michael J. Burns, eds. Haddad and Winchester’s Clinical Management of Poisoning and Drug Overdose. 4th ed. Philadelphia: Saunders, 2007. Print.

Substance Abuse and Mental Health Administration. “Drug Abuse Warning Network, 2006: National Estimates of Drug-Related Emergency Department Visits.” Aug. 2008. Web. 3 Apr. 2012.

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