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JoanDublin - It's quite common for people with ME to develop reactions to medications, and it's possible to lose tolerance to medications even without ever having taken them. This is often known as Central Sensitivity Syndrome, where the "Central" refers to the central nervous system.
Dr. Cheney theorizes that this is due to oversensitivity of the NMDA receptors in the brain; such oversensitivity is posited by many of the top researches, even when it's not central to their theories. Dr. Cheney recommends a combination of Klonopin (to up-regulate the GABA receptors) and magnesium (to down-regulate the NMDA receptors). Both drugs have the beneficial property of improving sleep. Magnesium is especially good at this, and may be able to help the sleep reversal problem.
Since your son is so sensitive to medications, you need to start with a very small amount of each to see if he'll tolerate them. If he does, higher doses can be used. Specifically, the magnesium is really helpful here, but it's hard to get a sufficient amount from supplements, as much of it passes straight through the body. For most people,
Dr. Sarah Myhill recommends magnesium injections, or magnesium via nebulizer. She's considered by many to be the best ME specialist in the U.K., and she can help you get treatments that you can't get from your GP. I'd strongly recommend getting in touch with her.