An overdose occurs when a toxic amount of a substance overwhelms the body, resulting in severe physical distress, loss of consciousness, or death. While the drug itself is the direct agent, specific behaviors drastically increase the probability of a fatal outcome. Understanding these high-risk actions is the first step toward preventing a tragedy.
Polysubstance Use
Combining two or more substances, known as polysubstance use, is one of the most dangerous behaviors leading to overdose. This practice is exceptionally risky because the combined effects are often synergistic, meaning the total impact is far greater than the sum of the individual effects. This is especially true when mixing two central nervous system depressants, such as opioids and alcohol or benzodiazepines.
Both opioids and alcohol slow the body’s processes, most critically the rate of breathing. When these depressants are taken together, their effect on the respiratory drive is compounded. This leads to a rapid and severe drop in breathing, which can quickly cause hypoxia (a lack of oxygen reaching the brain). This respiratory depression can progress to a fatal halt far faster than if either substance were consumed alone.
An equally dangerous interaction occurs when a depressant is combined with a stimulant, such as mixing alcohol with cocaine or heroin with methamphetamine. The depressant masks the initial stimulating effects, encouraging the user to consume more of one or both substances to achieve the desired effect.
Once the masking effect wears off, the true concentration of both drugs hits the system simultaneously, leading to unpredictable and lethal outcomes. The combined strain on the cardiovascular system from the stimulant, coupled with central nervous system depression, creates an extreme risk of heart failure, stroke, or respiratory arrest. Nearly half of all fatal overdoses involve multiple drugs.
Changing the Method or Pace of Use
Shifting the way a substance is used or the timing of use introduces sudden changes to the drug’s impact. One high-risk behavior is using the same dose after a period of abstinence, which results in a severe loss of physiological tolerance. After even a few days of reduced or no use, the body’s previous adaptation to the drug’s effects, especially opioid respiratory depression, is significantly diminished.
A dose that was once tolerated can become lethal because the margin between the desired effect and the life-threatening respiratory-suppressing effect has narrowed dramatically. This loss of tolerance is a common cause of fatal overdose following periods of detox, release from incarceration, or a break in use.
Another high-risk behavioral change is altering the route of administration, such as switching from swallowing or snorting a substance to smoking or injecting it. Ingestion and snorting allow the drug to be absorbed more slowly, providing a natural buffer as the body metabolizes the substance. Smoking or intravenous injection delivers a much higher concentration of the drug to the brain almost instantly, leading to a sudden, overwhelming onset of effects.
This rapid delivery bypasses the body’s initial filtering and metabolism mechanisms, resulting in a much higher peak concentration in the bloodstream and brain. The resulting “rush” can quickly turn into respiratory arrest, which is why methods offering the fastest absorption carry the highest risk of immediate overdose. Purchasing substances from unregulated sources introduces the variable of unknown potency, removing the ability to gauge a safe dose.
Street drugs are frequently contaminated with highly potent synthetic opioids, such as illicitly manufactured fentanyl, which can be 50 to 100 times stronger than morphine. Contamination often occurs unintentionally when drugs like cocaine, methamphetamine, or counterfeit prescription pills are mixed with trace amounts of fentanyl. Consuming what is believed to be a non-opioid or less potent drug can result in a fatal fentanyl overdose because the user is exposed to a toxic dose they did not intend to take.
Misusing Prescribed Medications
Behaviors involving legally obtained pharmaceutical drugs also increase the risk of overdose. One such behavior is dose escalation, which involves taking more medication than prescribed or taking it more frequently than directed. This is particularly hazardous with opioids, where taking a higher dose than recommended raises the risk of respiratory depression and coma.
Another dangerous behavior is taking a medication prescribed to someone else. This removes all medical oversight, meaning the user is unaware of the correct dosage for their body weight or tolerance level. They are also blind to potentially fatal interactions with other medications or existing health conditions, creating an immediate and unknown risk profile.
Altering the medication’s intended form, such as crushing an extended-release tablet to snort or inject, is also a high-risk behavior. Extended-release pills are designed to release the drug slowly over many hours; crushing them releases the entire dose at once. This sudden surge into the bloodstream can instantly overwhelm the body, leading to immediate overdose and severe complications like a bacterial infection of the heart lining.
Using Alone and Safety Planning
Using substances when no one else is present does not cause an overdose, but it is the single factor that turns a non-fatal overdose into a fatality. When an overdose occurs, breathing slows or stops, and without intervention, brain damage begins within minutes. Using alone eliminates the possibility of anyone administering the life-saving reversal medication naloxone or calling emergency services.
The immediate behavioral change to mitigate this risk is engaging in safety planning. This includes always having the opioid overdose reversal medication naloxone (Narcan) immediately accessible and letting others know when and where use is taking place. Naloxone is an antagonist that quickly attaches to opioid receptors, reversing the effects of an overdose and restoring breathing within minutes.
For those who must use alone, a crucial safety step is utilizing a peer-run overdose prevention hotline, such as the Never Use Alone service. A caller provides their location and stays on the line with an operator; if the caller becomes unresponsive for a set time, the operator alerts emergency medical services. This ensures that help can be dispatched quickly, bridging the critical time gap that determines survival.