A few years ago, a new ally emerged in the battle against antibiotic-resistant bacteria. A drug called thioridazine used to be used to treat schizophrenia, but it has fallen out of favor for mental illness in recent years. Now scientists think they have a better understanding of why thioridazine works on conditions such as MRSA that do not respond to most antibiotic treatments. There are new indications that the medication is helping to break down cell walls in infectious bacteria even when those bacteria are resistant to ordinary antibiotics. That means that this medication can be used even for hardened strains of illnesses.
Thioridazine was introduced in 1978 for patients with schizophrenia. Though often effective for that condition—as well as insomnia and heroin withdrawal symptoms—there were some concerns about side effects. Many patients reported agitation and restlessness, in many cases leading them to stop taking the drug. Patients also reported drowsiness, dizziness, and vertigo, as well as mouth tremors. Moreover, long-term use was found to carry some risks of heart diseases and vision problems, since it was found that excess thioridazine is stored around the heart and behind the retinas of the eyes. Because of these and other concerns, thioridazine was largely dropped as a schizophrenia treatment by 2005.
The researchers who discovered the mechanism point out that thioridazine doesn’t kill the bacteria on its own; it makes the heretofore resistant bacteria once again vulnerable to antibiotics. It does this by removing the amino acid glycine from the bacterial cell walls. This weakens the walls, making it possible for antibiotics to get in and kill the cells even when resistance has developed.
The next step, according to members of the research team, is to determine what properties of thioridazine have this effect, and attempt to isolate them. That way, either antibiotics themselves can be redesigned to target glycine as well, or a medication can be developed that eliminates glycine, but without the other effects of thioridazine. The elements that make it an effective treatment for schizophrenia can also make it dangerous for people without the mental illness, and the side effects are also a concern. Researchers will be investigating ways to selectively eliminate the drug’s anti-psychotic properties.