<s>[INST] Hi I have a 7 year old nephew who is autistic. He recently started guanfacine 1mg amn (about a month), one half tab twice daily. he also takes melatonin to help him sleep, the melatonin occasionally stops being effective however this time around the doctor prescribed clonidine 0.1mg uni one half tab in evening with tenex to replace melatonin. ( that started 3 days ago) My understanding is it will reset his melatonin in his body so he can then again use melatonin to help him fall to sleep.... Unfortunately I was unaware he had started this med and I gave him his full dose of melatonin last night. I am unsure how he slept the 1st night but last night he awoke several times throughout the night screaming and crying, He does not communicate well because of the autism but when asked he indicated his tummy hurt. Tonight now aware of this new med I did not give him melatonin and again he awaoke even worse that last night. So out of character that I wondered if perhaps he was having a night terror, I could not tell if he was truly awake of not. I was very concerned that he was in some type of legitimate pain that he could not communicate to me. he has gone back to sleep now but his mother said she was told this is normal. It is his bodies way of dealing with resetting itself ...... His mother, We all do need help for him so he s well rested among other things but I am concerned. I grew up with a bipolar brother I am very educated in ADD meds, ect but this is my first time using melatonin and I have never heard of this use for the drug nor can I find much online with regards to resetting the bodies anything, please help me understand if this is a common use, side effects, other possible options. Thank you! Chris [/INST] Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Melatonin is known as the sleep hormone. It helps to make a person fall asleep. Which means it just help you to get your sleep but not maintain it. normally it is been produced in everyone of ours body when we try to sleep. Using melatonin in low dose does not have much side-effects. Hope I have answered your query. Let me know if I can assist you further. </s>