Here is a package insert for dexidrine (which includes posible exacerbation of tics):
http://us.gsk.com/products/assets/us_dexedrine.pdf#search='d exedrine%20prescribing%20information'
A bunch of information for tics:
http://tourettenowwhat.tripod.com/tics_and_stimulants.htm
Sometimes clonidine or guanfacine are given with methylphenidate to reduce tics, and since they also help with some ADHD symptoms, they may allow your doctor to lower the stimulant dose...Worth discussing with your doctor.
http://www.indegene.com/Psy/Home/indPsy_Ind_News_09-08-2001_ 1.asp
http://www.cincinnatichildrens.org/health/info/neurology/dia gnose/tics-tourette.htm
It can be difficult to go through finding the most effective treatment to help your child, especially when there are side effects complecating the treatment optimization.
Good luck with this journey.
My son's facial tics worsened on several stimulants, including Concerta, Adderall and Focalin. We used Clonidine to calm his tics (he is now off all stimulants so we have no need for Clonidine at this point).