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Background and Basics on Drug Overdoses


Overdose Background and Basics  (BACK TO OVERDOSE 101)

Overdose happens when a person takes more of a drug or combination of drugs than the body can handle. As a consequence, the central nervous system (CNS) is not able to control basic life functions. The person may pass out, stop breathing, have heart failure, or experience seizures. Overdose can be fatal, although in a majority of cases it is not. However, there are ways to prevent overdose from happening and ways to respond if it does. The difference between life and death in the event of an overdose greatly depends on how witnesses react and take care of the person who has overdosed. It is important to remember that anyone can overdose. First-time users, long-time users, old people, young people, and everyone in between are susceptible. There is no exact formula for determining how much of a certain drug, or combination of drugs, will lead to an overdose. Individual characteristics such as a person’s weight, health, tolerance for a drug at a particular time, drug potency, route of administration, and speed of use all play a role in determining how much a person’s body can handle. The amount of a drug (or drug combination) that causes a person to overdose can fluctuate, so users should be advised that there is no such thing as a real “safe dose.”

What Happens to the Body During an Overdose?  (BACK TO OVERDOSE 101)

What happens in the body during an overdose is determined by what kind of drug is overwhelming the body’s systems. The primary distinction necessary for understanding overdose is the distinction between “depressants” (drugs that slow down CNS processes) and “stimulants” (drugs that speed up CNS processes).

desciption if the central nervous system

The Central Nervous System and Drugs

Basically, depressants act by slowing down the body. Widely used depressant drugs include opiates (such as heroin, methadone, and opium), benzodiazepines (such as Valium and Klonopin), barbiturates (such as phenobarbital), and alcohol. A person overdosing on depressants may fall into an extended “nod out,” become unresponsive or unconscious, have difficulty or stop breathing, or vomit. Fatal overdose is most often the result of breathing failure, and sometimes raspy and infrequent breathing is a sign of a problem. On the other hand, stimulants speed up CNS processes, such as heart rate and breathing. A stimulant overdose occurs when a person has a seizure, or when the heart beats so fast that it gives out and causes a heart attack or stroke. Generally speaking, stimulant overdoses appear to be much less common than opioid overdoses. The extreme agitation or panic that some people commonly refer to as “stimulant overdose,” while unpleasant, are NOT symptoms of a true overdose, and are more accurately described as a product of several factors, often including the drug itself as well as lack of sleep or dehydration. A person experiencing a true stimulant overdose may stop breathing, have seizures, or suddenly collapse or lose consciousness. Widely used stimulant drugs include cocaine and amphetamine-type stimulants (ATS), including “speed”, methamphetamine, and ecstasy. In the case of both stimulant and depressant overdose, the biggest problem occurs when a person cannot breathe adequately. If a person cannot breathe, oxygen cannot get to the brain. It takes only a few minutes without oxygen for the brain to suffer serious, often fatal damage.

Many Drugs are Unlikely to Cause Fatal Overdose  (BACK TO OVERDOSE 101)

There are many, many drugs that people take to get high or deal with problems, but relatively few can cause fatal overdose (or any overdose at all). It is essentially impossible, for example, to overdose on any kind of cannabis, which is one of the least toxic drugs known. Psychedelic drugs such as LSD or “magic mushrooms” also cannot, in general, cause overdose. They will, however, severely disorient someone if taken in high doses, and can cause dangerous behavior. Benzodiazepines such as fenazepam, nitrazepam, and lorazepam— commonly prescribed as anti-anxiety medications and often taken recreationally—rarely cause fatal overdose on their own except in extremely high doses.


The drugs with the greatest potential to cause fatal overdose are depressant (mostly opioids) and stimulant drugs that are injected, including heroin, prescription opiates; methamphetamine; cocaine; and amphetamine-type stimulants. Barbiturate pills (such as Seconal or Amytal) can cause fatal overdose, though in the past 30 years barbiturates have largely been replaced by benzodiazepines in most countries. Mixing increases risk. Drugs that may be low risk for overdose alone, especially drugs with the same effects, can greatly increase risk of overdose when combined. Drinking alcohol or taking benzodiazepines with heroin or other depressants is much riskier than using heroin alone. Mixing benzodiazepines with other CNS depressants, including alcohol, can also be extremely dangerous.


chart displaying drug classifications

Drugs by Class


Duration in which opiates are potent in your system

Opioids, Duration and Potency


Duration that drugs are potent in your system

Stimulant’s Duration and Potency 

Signs of Overdose: What to Look For  (BACK TO OVERDOSE 101)

Signs of Overdose

Recognizing Overdose  (BACK TO OVERDOSE 101)

It is sometimes difficult to determine if a person is in the danger zone for overdose. This section provides tips for recognizing if a person is overdosing and requires help. An overdose rarely sets in immediately the way it is portrayed in the movies. The case of finding a person with a needle still in their arm, for example, is uncommon. Instead, most overdoses set in over the course of hours, as a person’s body slowly shuts down and breathing becomes more labored (in opioid overdose) or repeated use of a drug over hours or days overwhelms normal cardiovascular function (in the case of stimulant drugs). It is important to stay with and monitor a person who is very high to make sure she does not go into an overdose as the drugs take full effect. Symptoms that may indicate an overdose is happening or is likely to happen are different for stimulant versus depressant drugs, and there is also a distinction between true stimulant overdose and stimulant “poisoning.” See the chart Symptoms of Overdose for warning signs of each.

chart displaying the common symptoms of an overdose

Symptoms of Overdose

Recognizing Stimulant Overdose  (BACK TO OVERDOSE 101)

Stimulants (like methamphetamine, amphetamines, and cocaine) speed up the body, which causes increases in heartbeat, blood pressure, and body temperature. A person who has truly overdosed on stimulants will collapse, and their heart or breathing may stop, or they may have a seizure. Other symptoms associated with intensive stimulant use, including extreme agitation or aggression, should not be mistaken for an overdose, but may be a sign that something is going wrong. Complaints of chest pain, shortness of breath, disorientation, and panic may be warning signs of an impending overdose and you should intervene or seek medical attention.


Recognizing Depressant/Opiate Overdose  (BACK TO OVERDOSE 101)

Depressants like opioids, benzos, or sedatives (like alcohol or tranquilizers) slow down the heart rate and breathing. A person overdosing on depressants may exhibit any of the symptoms in the chart above.   A person who is overdosing will not necessarily exhibit ALL of these symptoms, but any of these symptoms is a reason to closely monitor the person and be ready for action. When a person is overdosing, he might not be aware of what is going on, so it is important for those around him to be familiar with warning signs. If a person is not breathing or turning blue, he requires immediate help. Do not wait for him to “get over it” or start breathing again on his own. If a person is not breathing, begin performing rescue breathing immediately. It only takes a few minutes without breathing for a person to die.

Using Noise and Pain to Assess Overdose  (BACK TO OVERDOSE 101)

If a person is not exhibiting immediate warning signs such as shallow breathing or turning blue, a good way to determine if she is in the danger zone for overdose is by using noise or minor pain to see if she is alert. If she does not respond to a normal tone of voice, try calling her name even louder and shaking her a little. If she responds, try to get her up and walk her around. If not, see if she responds to minor pain stimulus like pinching her earlobes or pressing and rubbing your knuckles across her sternum. Unresponsiveness to noise or pain is a sign that the person may be overdosing. As mentioned above, overdose can take a few hours to set in. A person can slip from being very high into an overdose without warning. Make sure to continue to check on anyone you think might be at risk to ensure the person is still breathing. If possible, get the person up and walk her around. If she is on the ground, lay her on her side in case of vomiting. Assessing a person for signs of overdose once is not enough. Stay alert, and keep checking in!

Pictures depicting the correct technique to perform a sternum rub

How to Perform a Sternum Rub and Breathing Check