(October 16, 2015) According
to new research, nicotine use over time increases the speed that codeine is
converted into morphine within the brain, by increasing the amount of a
specific enzyme. It appears smokers’ brains are being primed for a bigger buzz
from this common pain killer – which could put them at a higher risk for
addiction, and possibly even overdose.
“We’ve known for some time that codeine was metabolized in
the liver, but we’ve now discovered that this is also happening within the
brain itself,” Dr. Rachel Tyndale, senior scientist in the Campbell Family
Mental Health Research Institute at the Centre for Addiction and Mental Health
(CAMH), and University of Toronto pharmacology, toxicology, and psychiatry
professor.
“Chronic nicotine use, or smoking, increases the amount of
an enzyme that converts codeine into morphine within the brain, increasing pain
relief. This may also make you more prone to addiction as the faster a drug
gives you a high, the easier it is for you to learn the behavior and become
addicted.”
These findings, published earlier this year in the
peer-reviewed journal Neuropsychopharmacology, contribute to a new way of
seeing the brain’s role when it comes to drugs and toxins. Instead of a passive
target with receptors idly waiting for drugs, Dr. Tyndale has found that the
brain is actually playing a much more active role than was previously thought.
Enzymes in the brain are busy breaking down – or ramping up – the effect of
drugs and other substances. Understanding these enzymes – and our genetic
variation affecting our brain’s metabolism – could help explain why people
react differently to drugs and toxins, and even why certain people are more
susceptible to complex diseases like Parkinson’s disease.