While abstinence is the surest path to an addiction-free life, researchers at the University of Montreal say how you take a particular drug will influence whether or not you become addicted to it. Smoking or injecting drugs exponentially increases your risk of addiction, they discovered in a recent study, which explored a range of substances from nicotine to cocaine.

Pharmacokinetics refers to the movement of a drug into, through, and out of the body. This scientific discipline studies how quickly a drug is broken down, how quickly it enters the bloodstream, how it becomes distributed through the body’s tissues, how fast it reaches the brain, how quickly it is metabolized, and when it is excreted. In a nutshell, pharmacokinetics describes the onset, duration, and intensity of a drug. While prescription drug-makers delve deeply into each of these matters, addiction specialists are less inclined to do so … and that’s a problem, say the researchers, because ignorance of these variables can lead to false conclusions.

“If we as drug addiction researchers ignore pharmacokinetics, we do so at our peril,” they noted. And so Dr. Anne-Noël Samaha, a professor in the department of pharmacology at University of Montreal and lead author of the study, and her colleagues conducted a study to explore which variables shape individual drug use and overall rates of addiction.

Speed and Fluctuation

To begin, the research team reviewed data concerning the speed of drug onset and patterns of drug consumption among those addicted to cocaine and amphetamines. Next, the researchers examined studies of the pharmacokinetics in animal models of addiction. Some of these studies focused on the link between intermittent, spiking brain levels and motivation to take a drug.

Among their first discoveries, Samaha and her colleagues found whenever a person smokes or shoots a drug (via intravenous injection), the amount of drug in the brain increases and decreases very quickly in comparison to when a drug is either swallowed or snorted. In fact, their investigation yielded a number of studies showing that I.V. cocaine users feel maximum intoxication within one to five minutes, while snorting cocaine users feel the effects most spectacularly at 15 to 20 minutes.

“Small variations in the speed of cocaine or nicotine onset have large effects on the neurobiological impact of these drugs,” noted the authors.

Next, the researchers discovered the importance of drug pharmacokinetics and its impact on dopamine, the neurotransmitter which is released into the brain’s pleasure centers during eating and sex. For instance, various studies indicate how often brain levels fluctuate may be critical to addiction since some drugs, including cocaine, are believed to work by blocking the dopamine transporter in the brain; this, in turn, floods the brain with dopamine. Importantly, rapidly rising and intermittent spikes in brain levels of cocaine (and its effects on dopamine) are decisive in predicting a person’s subsequent appetite for the drug, the researchers say.

It is estimated, among recreational users, 15 to 30 percent will become addicted, depending on the drug. Having surveyed the data, Samaha and her colleagues believe pharmacokinetics contribute to this distinction. “The clinical data are clear; the faster drugs reach the brain, the more likely it is that addiction will develop,” they concluded.

Source: Allain F, Minogianis EA, Roberts D, Samaha AN. How fast and how often: The pharmacokinetics of drug use are decisive in addiction. Neuroscience and Biobehavioral Reviews. 2015.