My son was supposed to only take guanfacine once a day in the morning but after it causing too much drowsiness, His doctor wants him to start taking it once a day at night and told me to start by giving him another dose this evening and there after only in the evenings. Is it OK that he would double his dosage for today? Since he took 2mg in the morning and now another 2mg in the evening, will he be OK for today? After today he will only be taking guanfacine 2mg in the evening at 7pm.