What Causes Red Blood Spot In Mouth After Taking Methipheidate?

hi dr my 7 yr old wen givin her methipheidate with in a hour she has red blood spot in side her mouth i stopped it thay went away restarted it it comming bk this medicaion she has used on and off for 2 yrs it the last 2 weeks wen putg her back on the spots appear and if medicaion is contiued it go to big red blood patches dnt undrstand why