Dear Dr. K: I’ve always heard that carbon monoxide is deadly, but then I read it’s being researched as a transplant medicine. What gives?
What gives is the dynamic of toxic levels versus helpful levels. There are many examples of this in the history of medicine. For example, in the pre-antibiotic era, heavy metals such as gold, silver and arsenic were used to treat infections, in very controlled doses.
Even oxygen, which we breathe every day, and can be supplemented for hospitalized patients can be toxic if given at too high a dose.
The same turns out to be true with carbon monoxide (CO). It wasn’t until fairly recently that scientists discovered humans actually produce CO, and that it plays a vital role in many bodily processes.
In the brain, it is a neuro-transmitter, important in learning and memory. In the heart, it keeps blood vessels wide open. In the liver, intestines, kidneys, lungs and reproductive organs it improves natural functions. And in the immune system it improves host resistance and lessens undesirable inflammation.
It is this last property that has led to the research you are alluding to in organ transplant rejection. Carbon monoxide has been shown to prevent transplant rejection in several animal models; it hasn’t been studied yet in humans.
Because CO reduces inflammation it also is being studied in traumatic brain injuries, multiple sclerosis, pulmonary fibrosis and atherosclerosis – all of which have unwanted inflammation as a common denominator.
Three methods of delivering CO as a treatment are being studied: breathing in small amounts, using CO-releasing compounds and using pro drugs to generate extra CO.
Perhaps being stuck in traffic has an upside.