Mellaril May Double As an Antibiotic

One of the oldest typical antipsychotic drugs is Mellaril (thioridazine), a member of the class known as the phenothiazine drugs. The earliest member of this class, methylene blue, was developed in the late 19th century. Today, Mellaril and its generic formulations are rarely prescribed, especially in the developed world. The well-documented list of side effects, coupled with the development of more effective and less toxic alternatives, has led to the virtual disappearance of Mellaril. Among the side effects of this medication are heart abnormalities that can lead to sudden death in otherwise healthy patients. However, another property of Mellaril has recently gotten renewed attention—namely, its ability to fight off bacterial and fungal infections.

In the last several years, the incidence of antibiotic-resistant strains of microorganisms has become a serious issue for public health officials. Drug-resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA) have made hospital infections a life-threatening danger, especially for those with compromised immune systems. Rates of tuberculosis infection have been on the rise, especially in poorer nations. The widespread use of powerful antibiotics has ironically resulted in tougher, harder to kill microbes. In response to this situation, some researchers are looking to older and unconventional treatment options.

The antibiotic properties of Mellaril have been known for a long time, although the exact mechanism of action is not completely understood. What is known is that only a relatively small dosage of the medication is required to bring about the antibiotic effects. The effective dose is only a fraction of that typically used to produce a psychiatric benefit. Presumably this will limit the dangers of cardiac side effects. Mellaril works by enhancing the effectiveness of traditional antibiotics. One theory maintains that the drug sabotages the defense mechanisms of microorganisms, leaving them open to attack.

In poorer nations still battling malaria, tuberculosis, and other communicable diseases, a cheap and readily available weapon is always welcome. The newest medications are often too expensive for poor nations to dispense to their citizens. If further testing continues to show antibiotic usefulness, then Mellaril may soon be a frontline treatment against some of the world’s deadliest and most drug-resistant microbes.

Thanacoody, H. K. R. (2007). Thioridazine: resurrection as an antimicrobial agent? British Journal of Pharmacology, 64(5), 566-574.

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