This route is also used to introduce drugs that fight certain infections, particularly post-neurosurgical. The drug needs to be given this way to avoid the blood brain barrier. The same drug given orally must enter the blood stream and may not be able to pass out and into the brain. Drugs given intrathecally often have to be made up specially by a pharmacist or technician because they cannot contain any preservative or other potentially harmful inactive ingredients that are sometimes found in standard injectable drug preparations.