Under the old Medicaid system, the rates were the same statewide. Now, pharmacists sign managed-care contracts agreeing to accept the “maximum allowable cost” reimbursement for medications, as determined by the health plan’s pharmacy benefit manager. Because the rates are proprietary information and are not subject to open-records laws, pharmacists do not know before signing a contract how much a health plan will reimburse or how its rates compare with those of other plans before signing a contract.

Stephanie Goodman, a spokeswoman for the commission, said that the decrease in reimbursement rates is “very much in line” with what the agency expected, and that it is the same for independent and chain pharmacies. The average dispensing fee paid to pharmacists for Medicaid prescriptions dropped from $7.13 to $1.53 in the new system, and pharmacists received $12.7 million less in dispensing fees in the first month than they would have under the previous system.

John Calvillo, president of the Rio Grande Valley Independent Pharmacy Association, said he has a list of 26 independent pharmacies that have closed or been sold to retail chains since the managed care changes. He said that CVS Caremark is largely to blame because it has the lowest reimbursement rates of the five managed care plans he accepts. And, he contended, it appears to be trying to poach independent pharmacies.

“In my opinion, it’s kind of a little conspiracy and the state is allowing this to happen,” Mr. Calvillo said.

In a memo distributed to CVS pharmacies in Dallas in March, Craig Goodson, a CVS supervisor, told pharmacists that the reduced dispensing fees might “put many independent pharmacy owners in a pinch that they have never before felt.” He asked CVS pharmacists to keep their “eyes and ears open” and pass along information on how the changes were affecting independent pharmacies. “This poses a huge opportunity for us to grow our company and the scripts and patients that we service,” he wrote.

Michael DeAngelis, a spokesman for CVS Caremark, said in an e-mail to The Texas Tribune that the company had not authorized Mr. Goodson to send the memo. Mr. DeAngelis added that “reductions to the Medicaid reimbursement rate in Texas are the same for both independently owned drugstores and retail chain pharmacies.”

The state contracts with managed care organizations include language requiring pharmacy benefit managers connected to a retail pharmacy, like CVS Caremark, to “ensure no conflicts of interest exist and ensure the confidentiality of proprietary information.”