I often have a different reation to what's expected, e.g. sleep med before an op kept me awake and a sedative had no effect whatosever, when most people act drunk on it. I don't tend to get the side effects listed on the info sheet, except with pseudoephedrine, which made me feel like I'd overdosed on caffeine and I didn't sleep for 3 nights, which is a known side effect.
My Mum, who is also probably on the spectrum, always has major reactions to everything. She was given anti-inflammatories for mosquito bites last year and seemed to go mildly insane. When she was trying to give up smoking, she had severe allergic reactions to 2 different types of nicotine patches, ended up going cold turkey and hasn't smoked in 9 years. She has chronic sciatica, due to osteoarthritis. The doc tried her with every kind of painkiller she could think of, each one made her violently sick. She now gets an injection for the pain. The only reaction she has to that is a red face for a few days, without itching, so she can live with that.
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"We act as though comfort and luxury were the chief requirements of life, when all we need to make us really happy is something to be enthusiatic about." Charles Kingsley