抗癫痫药物.ppt

Antiepileptic Drugs Department of Pharmacology Zhang Yan-mei Nature of Epilepsy Epilepsy affects about 0.5% of the population. The characteristic event is the seizure, which is often associated with convulsion, but may occur in many other forms. The seizure is caused by an abnormal high-frequency discharge of a group of neurons, starting locally and spreading to a varying extent to affect other parts of the brain. Nature of Epilepsy Seizures may be partial or generalised depending on the location and spread of the abnormal neuronal discharge. The attack may involve mainly motor, sensory or behavioural phenomena. Unconsciousness occurs when the reticular formation is involved. Types of Epilepsy Partial seizures The discharge begins locally, and often remains localised. Produce relatively simple symptoms without loss of consciousness. Types of Epilepsy Generalised seizures Involve the whole brain, including the reticular system, thus producing abnormal electrical activity throughout both hemispheres. Immediate loss of consciousness. Nature of Epilepsy Two common forms of generalised epilepsy are the tonic-clonic fit (grand mal) and the absence seizure (petit mal). Status epilepticus is a life- threatening condition in which seizure activity is uninterrupted. Nature of Epilepsy The neurochemical basis of the abnormal discharge is not well understood. It may be associated with enhanced excitatory amino acid transmission, impaired inhibitory transmission, or abnormal electrical properties of the affected cells. The glutamate content in areas surrounding an epileptic focus is often raised. Nature of Epilepsy Repeated epileptic discharge can cause neuronal death (excitotoxicity). Current drug therapy is effective in 70-80% of patients. Mechanism of Action Current antiepileptic drugs are thought to act mainly by two main mechanisms: Mechanism of Action Reducing electrical excitability of cell membranes, possibly through inhibition of sodium channel. Enhancing