This class of drugs does not lend itself to the type of organization used in many other chapters. Here we need to consider the disease to be treated.
Epilepsy is a chronic disorder characterized by recurrent episodes in which the brain is subject to abnormal excessive discharges (seizures) synchronized throughout a population of neurons. The seizures themselves have been classified to assist with demographics and treatment. The accompanying table provides a simplified seizure classification scheme.
|Seizure Type ||Clinical Manifestations |
Partial (focal, local)
Partial seizures with secondary generalization
Generalized convulsive (tonic-clonic, grand mal)
Generalized nonconvulsive (absence, petit mal)
Focal motor, sensory, or speech disturbance. No impairment of consciousness.
Dreamy state with automatisms. Impaired consciousness.
Loss of consciousness, falling, rigid extension of trunk and limbs. Rhythmic contractions of arms and legs.
Impaired consciousness with staring and eye blinks.
Notice that some of these seizures do not involve muscle jerking or convulsions. In particular, absence seizures are called nonconvulsive. Technically, this would make the name anticonvulsants inaccurate, but it is often used to designate this class of drugs.
Now that we have defined the types of seizures we want to control, we can start examining the drugs. To simplify this organization, let's consider which drugs are used for which types of seizures. There is not 100% agreement on which is the best drug in each category, so do not be bothered by discrepancies between textbooks.
|Seizure Type ||Drugs of Choice |
Partial, including simple, complex and secondarily generalized
We have covered the drugs of choice for all of the major types of seizures using only six drugs. In addition to these drugs, you should be aware that there are others available.
IMPORTANT DETAILS ABOUT THE MOST IMPORTANT DRUGS
VALPROATE is associated with elevated liver enzymes, nausea and vomiting, and weight gain. It can also produce a tremor.
Valproate may produce fatal hepatic failure. This is most common in children under the age of 2 years who are taking more than one antiepileptic drug. The hepatotoxicity is not dose related; it is considered to be an idiosyncratic reaction.
CARBAMAZEPINE causes autoinduction of its own metabolism.
Carbamazepine is metabolized by the liver and over a period of several weeks induces the enzymes that metabolize it. Therefore, an initially adequate dose gradually produces lower and lower plasma levels as the liver increases the metabolism (shortening the half-life). Carbamazepine has been associated with granulocyte suppression and aplastic anemia.
Oxcarbazepine is chemically similar to carbamazepine, but ...