A recent study suggests that the method of drug administration, whether injected or taken orally, can impact the brain’s reaction to medication. Conducted by a team from the US National Institutes of Health (NIH), this study was designed to explore the connection between rapid drug delivery to the brain and addiction.
According to the researchers, drugs that enter the brain more quickly through injection tend to be more addictive, and the addictive quality is linked to the release of dopamine. The study also found that the brain’s salience network is activated when drugs are taken intravenously, but not when taken orally. Psychiatry expert Nora Volkow from NIH states, “We’ve known for a long time that the faster a drug enters the brain, the more addictive it is – but we haven’t known exactly why.” She adds, “Now, using one of the newest and most sophisticated imaging technologies, we have some insight.”
The study utilized the prescription stimulant methylphenidate in 20 participants who did not have ADHD. The drug was administered both intravenously and orally, and participants reported their observations on how they felt after taking it. In addition to self-reported observations, PET scans were used to monitor dopamine levels in the brain, while fMRI scans were used to monitor overall brain activity.
The fMRI scans revealed differences in the salience network’s activity after injections, particularly in the dorsal anterior cingulate cortex and the insula cortex, which are linked to feelings of euphoria and addiction. This information is essential for understanding drug addiction and how treatments should be administered to patients. The potential next step is to investigate the effects of deliberately blocking activity in the salience network to determine its impact on the feeling of being high.
Volkow emphasizes the importance of understanding the brain mechanisms behind addiction for developing prevention interventions and new therapies. The research has been published in Nature Communications.