The strange tale of the antibiotic that kills fear

I heard about this the first time from Prof Isaac Marks. He was talking about ways of making the treatment of extreme fears of stuff — or phobias — more effective. He described how, using an antibiotic, one could make a treatment session more effective. I remember being skeptical, but this was Isaac Marks and when Prof Marks says something about treating phobias you listen. There are other medications that have been used for one thing and then turned out to be helpful for another; so the idea isn’t as strange as it may seem. Aspirin is the best known example of this: used first as a painkiller and then found to be also useful in reducing the risk of strokes and heart attacks.

Made by bacteria to kill bacteria

Of course Prof Marks was right. The antibiotic in question is called cycloserine and it was discovered by two microbiologists, Roger Harned and Eleanore Kropp, in 1955. They found it when working with bacteria called streptomyces orchidaceus, which make it. To this day drug companies use these bacteria to produce it. Doctors used it to treat tuberculosis and other infections. That was its only use for many years.

Doctor, can this antibiotic change my emotions?

Some people using this antibiotic experienced side-effects affecting their emotional health, which led doctors to investigate why this was happening. It turned out cycloserine affects the way a chemical works in a particular area of the brain. This particular area is called the amygdala.

Enter the amygdala

The amygdala is the size and shape of an almond and — among other things — it is very important when forming memories of things we become fearful of. Sometimes these fears are very useful and they make us avoid harmful things. Sometimes this doesn’t work so well and one can become fearful of something that is really not that harmful. When researchers discovered that some of the side-effects of cycloserine were because of its effects on the amygdala the light bulb went off. They thought cycloserine might be able to help get rid of those undesirable strong fears by making therapy more effective.

OK, nice theory, but does it really work?

Being a cautious lot, researchers from Emory University began experimenting with rats in 2003. They started by making rats severely fearful of a certain situation and then they gave them cycloserine when helping them overcome their fear (yes, as strange as it sounds you can treat rats for their phobias). They compared them with rats not taking the cycloserine but going through the same treatment. Their results were that the rats using cycloserine got better sooner.

Encouraged by their findings they went on to try this on people suffering from acrophobia (fear of hights). They already knew cycloserine was safe in people as it had been used as an antibiotic for 50 years. Their results were also very encouraging. It seemed that those using the cycloserine in therapy improved much more than those not using it. You can read their paper here.

Other researchers have since shown the same effects in other phobias and also with other conditions associated with anxiety and stress. In 2008 a paper by Melissa Norberg and her team looked at all the research done with cycloserine up to that time and concluded that it is clearly useful in therapy. They found that it is best to use right before or after therapy, but not otherwise, and that it was no good giving it too many times.

Odd but true

So, there you have it. My guess is that — even though cycloserine started off as an antibiotic — it is now used probably more often when treating phobias and other anxiety complaints. It is not without its side-effects so sometimes we cannot use it. That is why people are looking for new drugs that do similar things in the amygdala, but not cause so many problems. If you have a phobia your doctor or therapist might talk to you about it and, when she or he does, you won’t think it so strange.

If you have taken cycloserine I would like to hear about it. Did it work? Did it cause any problems? Please leave a comment and share your experience.

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