You don't have to anger your husband and tell your son, you could just ask your son if he ever reads the labels on his medicines to know the side effects are and let you know if he encounters any.
My 16 year old son always reads his inserts. His medicine, his information. (fyi, he does not take anything anxiety medications, but he is taking some heavy duty skin medication)
Personally, I think a 16 year old should be fully informed and involved in decision making for everything they take. Unless on all levels they don't function as 16 year olds. Then factor in their mental age and decide accordingly.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).