From acne to nerves
Minocycline was originally developed to aid in the treatment of acne. As an oral antibiotic, it would kill the microorganisms responsible for infecting the skin cells, leading to more clear skin.
It also proved efficacious against other infections, such as respiratory tract infections, urinary tract infections, and even sexually transmitted diseases such as gonorrhea and syphilis.
It can also be used to treat MRSA, at least for now. It is indeed a broad-spectrum antibiotic.
Unfortunately, minocycline does have its downsides. Part of what makes it so effective is that it is very lipid-soluble, which means that it dissolves into fats and gets transported throughout your body rather easily.
That ease of transportation means that it can penetrate into your nervous system and maybe even cause negative side effects. Most commonly it causes vertigo, though it can cause diarrhea, skin discoloration, and even autoimmune disorders or—rarely—brain swelling.
That does not sound so promising as a treatment for multiple sclerosis, right?
Remember how minocycline penetrates into the nervous system? That can be a good thing, as you well know that multiple sclerosis involves degeneration of parts of the nervous system.
When contacting the nerves, minocycline shows both neuroprotective and neurorestorative properties. It also has anti-inflammatory actions, halting the creation of cytokines, which trigger the inflammation response. It can also block haywire immune system cells, T-cells, from accessing the nerves in the first place.
The same medication which can affect the nervous system negatively for healthy people appears to be able to affect the nervous system positively for people with neurodegenerative disorders such as multiple sclerosis.