CVS Caremark’s fourth-quarter earnings climbed 6 percent, as new customers and Medicare prescription drug plans helped its pharmacy benefits management business, and revenue from the chain’s established drugstores grew.

The Woonsocket, Rhode Island company said Wednesday it earned $1.13 billion, or 90 cents per share, in the three months that ended Dec. 31. That compares with earnings of $1.06 billion, or 81 cents per share, in the same period in 2011.