The best thing to do would be to check with your manager. I know that some institutions allow LPN's to give medications through a central line and others do not. Always adhere to your institutions policy and procedure in this regard. If your institution doesn't allow this you could act as a change agent to get the policy changed.
LPNs are generally not allowed to administer medications through any IV line without specialized training. For example, in the state Iowa (where I live) this is the major difference between LPNs and RNs. As an RN, my program of study included how to adminster medications through IV lines safely. In order to determine if LPNs may administer medications through an IV line check with your state's board of nursing.