An old antibiotic that’s been around since the 1970s could be repurposed to be a new antidepressant. So far, researchers from the Deakin University have gathered data from the first clinical trial showing that minocycline can improve outcome for people with major depression.
The researchers began their investigation with the observation that depression can be accompanied by cellular inflammation. "There is evidence to suggest that people with major depressive disorder have increased levels of inflammation in their body," said Dr. Olivia Dean, the study’s lead author.
Based on this observation, the team set out to investigate whether treating the inflammation with antibiotics could alleviate symptoms of depression. They chose minocycline because this drug has been shown to “reduce oxidative stress and promote neuronal growth.”
"Specifically, minocycline reduces brain inflammation in cell models, and thus we wanted to see if it was useful for people,” said Dr. Dean.
Of note, minocycline is a broad-spectrum antibiotic that is often used to treat acne vulgaris. Other infections for which minocycline is prescribed include urinary tract infections, respiratory infections, gonorrhea, tick fever, and chlamydia.
The current clinical trial involved 71 people diagnosed with major depression. Patients were randomized to a 12-week trial in which they either received minocycline or placebo in addition to usual treatment for major depressive disorder.
"We found that those on minocycline reported significant improvements in functioning, quality of life, global impression of their illness, and there was also a trend towards improvements in anxiety symptoms,” said Dr. Dean.
It's exciting when a pre-existing drug shows promise for a new disease because things tend to move much faster when this happens. "Existing medications have known safety profiles and are readily accessible," explained Dr. Dean. With the toxicity and pharmacokinetics of a drug already known, makers can shave off as much as 15 years off the pipeline to get the drug to patients' hands. But given the small size of the trial, the team is cautiously optimistic about the antibiotic’s function as a new antidepressant. However, the results suggest a broader implication, that there are great but untapped potential for old drugs. "We've found that using old medications for new purposes is very useful," she said.
"Current antidepressants are useful, but many people find a gap between their experience before becoming unwell and their recovery following treatment," Dr. Dean said. "We aim to fill this gap by providing new, biologically-based, treatments for depression. We're also considering a study of minocycline for people with anxiety disorders, given what we have found in this study.”
Minocycline is not without side effects. Most notably, the drug can cause harm to the unborn fetus or newborn babies who take breastmilk. Other common side effects include dizziness, headache, vomiting, and increased sensitivity to sunlight.
Additional sources: MNT
