I m currently taking one Vynanse 40 mg /day as prescribed. I m 38, female, 5 7 and 135 pounds. I have noticed after several months without any worrisome side effects, that after 4-5 hours, I get a headache no OTC meds will remedy, along with a stiff neck, like my muscles are tense. I do chase after a two year old all day, and they likely are, but this seems different.