Antidepressants may help deliver other drugs to the brain

Since the 1980s, selective serotonin reuptake inhibitor (SSRI) antidepressants have been the mainstay of treatment for depression and other mental disorders around the world. In the UK alone, tens of millions of prescriptions for these drugs are written every year. However, their mechanisms of action and their broader effects on the body are still not fully understood.

Now, research led by scientists at King's College has been published in the journal of Molecular Psychiatry, identifying a key biological process targeted by SSRIs and suggesting new clinical applications for these drugs.

In this study, all current SSRIs were tested on different types of cells grown in petri dishes, using drug concentrations similar to those found in the blood of patients being treated for depression. Surprisingly, almost all antidepressants affect the ability of cells to transport materials in and out through a process called membrane trafficking.

What's more, a single injection of the antidepressant fluvoxamine into mice allowed a fluorescent compound that normally remains outside the brain to accumulate inside the brain, breaking through the cellular barrier that separates the brain from the rest of the body.

Dr Oleg Glebov, from King's IoPPN, said: 'Given how little is known about the wider effects of antidepressants, we wanted to find out more about how these drugs affect cells in our brains and bodies. We found that most antidepressants regulate the same key biological process in many tissues, which likely has little to do with their effect on depression.

“In addition, our data suggest that a single dose of an antidepressant may be sufficient to effectively open the blood-brain barrier to the delivery of other drugs. We hope this discovery will help improve the clinical effectiveness and reduce the cost of treatment with new dementia drugs that are currently out of reach for the millions of people who need them. In addition, we are excited about the opportunity to explore whether antidepressants can help deliver medications to other hard-to-reach areas of the body."

Exactly how SSRIs control membrane traffic remains unclear, and elucidating the molecular intricacies will require collaboration across multiple scientific disciplines. It will also be necessary to determine in a clinical setting how suitable SSRIs are for delivering other drugs into the human body.

However, it is possible that this study could mark the beginning of a new era for these venerable drugs, which have been around for more than 30 years - this time by helping other drugs do their job.