Health Affairs published a study investigating the relationship between states' Medicaid prescription drug spending and their policies on substituting generic drugs in the program.  The authors found that states without requirements for patient consent had the highest generic utilization rates, and suggested that policymakers consider mandating the use of generics where possible to reduce Medicaid spending.

Shrank, W. H. et al.  (2010).  State generic substitution laws can lower drug outlays under Medicaid.  Health Affairs, 29(7): 1383-1390.  doi: 10.1377/hlthaff.2009.0424.  http://content.healthaffairs.org/cgi/content/abstract/29/7/1383 

Authors: William H. Shrank, Niteesh K. Choudry, Jessica Agnew-Blais, Alex D. Federman, Joshua N. Liberman, Jun Liu, Aaron S. Kesselheim, M. Alan Brookhart and Michael A. Fischer