A long-term drug addict injects himself with the same dosage of heroin twice over a period of two days. The first time, he is fine. He feels happy, buzzed, relaxed – all of the desirable things that come from using the drug. The second time, he overdoses.
This is not a riddle, but a very real, very frightening possibility for anyone who has ever abused a substance with the potential for overdose. Not every overdose occurs because an addict gets sloppy and makes a wrong measurement or decides to take a little more of the drug than usual. Sometimes, people overdose because, for some inexplicable reason, their usual dosage has unusual effects. The same amount of the same drug can feel perfect one day, but nightmarish the next.
What is tolerance?
Most people are familiar with the concept of tolerance, or the way in which the central nervous system adapts to an addictive substance. When people first try coffee, they might feel jittery after one cup – however, after continuing to consume coffee for a prolonged period of time, they eventually need more of it to feel the same effects.
When people use drugs heavily, they have likely spent months – or years – developing their level of tolerance. They are likely taking a considerably higher dosage than when they first started. This dosage might be so strong that it would be unpalatable or even dangerous to a new user; however, because the long-term user has developed tolerance, this high dosage is comfortable and ideal.
Tolerance, however, is not static. Most people recognize that if they stop using drugs for a long period of time, their tolerance decreases, making their previously normal dosage too intense. Fewer people are aware that tolerance has the potential to decrease over the course of days or even hours.
When people’s tolerance changes without realizing it, they can overdose on a dosage that they had safely taken before.
What changes tolerance?
The brain does not exist in a vacuum. When a person takes a drug, their neurons are not only processing the newly consumed drug – they are also processing the context surrounding the drug: For example, brain cells can also be focused on the user’s mood, the color of the walls or the weather outside. This context can actually be vital to tolerance.
In a seminal study, a group of researchers found that rats that had developed tolerance to morphine immediately lost that tolerance when given morphine in a new environment. In a later study by the same research group, administering drugs to rats in a new environment caused a majority of the animals to overdose despite the dosage being “safe” when administered in a familiar environment.
In other words, taking a drug in a new or different environment is enough to cause an overdose.
Classical conditioning and tolerance
Ivan Pavlov performed a famous series of experiments, in which he taught a dog to associate the sound of a bell with food. Each time Pavlov rang a bell, he gave the dog food. Eventually, ringing the bell was enough to make the dog salivate in anticipation for the food to come.
Tolerance works the same way. If people usually takes drugs in their bedroom, their brain begins to associate the drug use with that specific room. The sounds, smells and look of the room all contribute to their development of tolerance. Upon experiencing the environmental cues, the human body instinctually prepares for the drug to enter the system, not unlike a dog preparing to receive a treat. If those environmental cues are not present, then the body does not adequately prepare for the drug. The brain is caught off guard, so to speak, which is enough to turn an ordinary dosage into a deadly dosage.
Researchers are still attempting to determine precisely which contextual cues have the potential to provoke an overdose. What happens if some parts of the environment change, but other components remain the same? How does a user’s current mood affect his or her tolerance? What about the weather?
One thing researchers know for certain, however, is that deaths from overdose are on the rise. It is important to remember that one small mistake can stand between a drug addict and death.
Sovereign Health Group provides individualized programs for drug addiction so that each patient can have the therapy that is best for him or her. Sovereign also provides patients with a safe, comfortable form of detox, known as Natural Assisted Detox, that can help conquer the first intimidating steps toward sobriety. For more information, please contact 888-530-4614.
Written by Courtney Lopresti, M.S. neuroscience, Sovereign Health Group writer