Test code links throughout this Guide refer to the corresponding test in the User's Guide. It is the drug of choice for treating general motor and focal seizures. It is also used for the prophylactic control of seizures developed during or after neurosurgery, following severe traumatic injury to the head, and in the management of patients with eclampsia or severe preeclampsia. Most drugs in the blood are bound to proteins.
Drugs bind to a number of proteins.
Some drugs, however, can bind to both albumin and globulins. A decrease in plasma proteins leads to a decrease in binding sites and, consequently, to an increase in free drug levels. Drug bound to protein cannot cross membranes and is pharmacologically inactive. In principle, therefore, measurement of free drug, rather than total drug, is more meaningful because free drug reflects the drug concentration available at the receptor site. In reality, physiological or disease states can alter the usefulness of both free and total levels.