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Anticonvulsants are drugs designed to prevent the seizures or convulsions typical of epilepsy or other convulsant disorders. Epilepsy is not a single disease—it is a set of symptoms that may have different causes in different people. There is an imbalance in the brain's electrical activity, which causes seizures. These may affect part or all of the body and may or may not cause a loss of consciousness. Anticonvulsant drugs act on the brain to reduce the frequency and severity of seizures.

Petit mal seizures may be so subtle that an observer will not notice that an individual is having one. Grand mal seizures are more dramatic and unmistakable. The patient may cry out, lose consciousness, and drop to the ground with muscle spasms in the extremities, trunk, and neck. The patient may remain unconscious after the seizure.

Anticonvulsant drugs are an important part of the treatment program for epilepsy. Anticonvulsant drugs are available only by prescription because they are so potent and toxic if taken in excess. Their consumption must be carefully monitored by blood tests. Once an individual has been diagnosed with epilepsy, he or she must continue taking the anticonvulsant drugs for life.

Anticonvulsant drugs include medicines such as phenobarbitol, carbamazepine (Tegretol), phenytoin (Dilantin), and valproic acid (Depakote, Depakene). The drugs are available only with a physician's prescription and come in tablet, capsule, liquid, and "sprinkle" forms. The recommended dosage depends on the type of anti-convulsant, its strength, and the type of seizures for which it is being taken.

Phenobarbital is an anticonvulsant drug that has been used since 1912 and it is still one of the better drugs for this purpose. Phenobarbital is used to treat infants (ages 0–1 year) with any type of seizure disorder, and other children with generalized, partial, or febrile seizures. It is also used for treatment of status epilepticus (seizures lasting longer than 15 minutes). The barbiturates, such as mephobarbital, and metharbital, are also sometimes used as anticonvulsants. Of the family of barbiturate drugs, these are the only three that are satisfactory for use over a long period of time. They act directly on the central nervous system and can produce effects such as drowsiness, hypnosis, deep coma, or death, depending upon the dose taken. Because they are habit forming drugs, the barbiturates probably are the least desirable to use as anticonvulsant drugs.

Tegretol is an antiepileptic drug. Types of seizures treated with Tegretol include: grand mal, focal, psychomotor and mixed (seizures that include complex partial or grand mal seizures). Absence seizures (petit mal) do not respond to Tegretol. Phenytoin is a close relative to the barbiturates, but differs in chemical structure. Phenytoin acts on the motor cortex of the brain to prevent the spread of the signal that initiates a seizure. Sudden withdrawal of the drug after a patient has taken it for a long period of time can have serious consequences. The patient can be plunged into a constant epileptic state. Lowering the dosage or taking the patient off phenytoin must be done gradually.

Valproic acid compounds are also antiepileptic drugs, though their mechanism of action is unknown. One of their major side effects is liver toxicity, appearing most often in young patients and in those who are taking more than one anticonvulsant drug.

Another class of anticonvulsant drugs, the succinimides, suppress the brain wave pattern leading to seizures and stabilizes the cortex against them. These are useful drugs in the treatment of petit mal epilepsy, and like phenytoin, must be withdrawn slowly.

Neurontin is another anticonvulsant medication belonging to the antiepileptic drug class. It is a medication used as add-on therapy with other antiepileptic medications to treat partial seizures common among adults over 12 years old with epilepsy.

Anticonvulsant drugs may interact with medicines used during surgery, dental procedures, or emergency treatment. These interactions could increase the chance of side effects. Anyone who is taking anticonvulsant drugs should be sure to tell the health care professional in charge before having any surgical or dental procedures or receiving emergency treatment. Some people feel drowsy, dizzy, lightheaded, or less alert when using these drugs, especially when they first begin taking them or when dosage is increased. Anyone who takes anticonvulsant drugs should not drive, use machines or do anything else that might be dangerous until they have found out how the drugs affect them. This medicine may increase sensitivity to sunlight. Even brief exposure to sun can cause a severe sunburn or a rash.

People with certain medical conditions, or who are taking certain other medicines, can have problems if they take anticonvulsant drugs. Before taking these drugs, be sure to let the physician know about any of these conditions. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

Birth defects have been reported in babies born to mothers who took anticonvulsant drugs during pregnancy. Women who are pregnant or who may become pregnant should check with their physicians about the safety of using anticonvulsant drugs during pregnancy. Some anticonvulsant drugs pass into breast milk and may cause unwanted effects in babies whose mothers take the medicine. Women who are breast-feeding should check with their physicians about the benefits and risks of using anticonvulsant drugs.

Anticonvulsant drugs may affect blood sugar levels. Patients with diabetes who notice changes in the results of their urine or blood tests should check with their physicians. Taking anticonvulsant drugs with certain other drugs may affect the way the drugs work or may increase the chance of side effects. The most common side effects are constipation, mild nausea or vomiting, and mild dizziness, drowsiness, or lightheadedness. These problems usually go away as the body adjusts to the drug and do not require medical treatment. Less common side effects may occur and do not need medical attention unless they persist or are troublesome. Anyone who has unusual symptoms after taking anticonvulsant drugs should get in touch with his or her physician.

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