Illinois lawmakers looking for ways to cut expenses in the state’s Medicaid program may consider the big-ticket cost of prescription drugs as a tempting target. Prescriptions cost the Illinois Medicaid program more than $1 billion a year. Medicaid covers drugs for a wide variety of illnesses, from asthma to schizophrenia, for the poor and disabled. Legislators are looking at other states for ideas. Tennessee, for example, limits adults to five prescriptions each month. Illinois officials estimate that a similar limit would save the state $136 million a year and affect 200,000 Medicaid clients who now fill more than five prescriptions per month.