Anticonvulsants / Anti-Seizure Medications
What are Anticonvulsants?
Anticonvulsants represent a diverse class of drugs indicated for the treatment of various types of seizures associated with seizure disorders such as epilepsy, a neurological dysfunction in which excessive surges of electrical energy are emitted in the brain, and other disorders.
The first effective anticonvulsant was potassium bromide, introduced in 1857. In 1910, phenobarbital, which then was used to induce sleep, was found to have antiseizure activity and became the drug of choice for many years. In 1940, phenytoin was found to be an effective for the treatment of epilepsy. The last ten years of the 20th century were called in neuroscience "decade of the brain". This period has brought many new antiepileptic drugs: vigabatrin, lamotrigine, topiramate, tiagabine, gabapentin, oxcarbazepine, levetiracetam and zonisamide.
How do Anticonvulsants work?
Anticonvulsants have different mechanisms of action on neuronal function, but they have the common property of functional blockade of voltage-gated Na+ channels.
Anticonvulsants depress abnormal neuronal discharges in the CNS that may result in seizures. They may work by preventing the spread of seizure activity, depressing the motor cortex, raising seizure threshold, or altering levels of neurotransmitters, depending on the type.
Anti-seizure medications are used as monotherapy or in combination with other medications depending on the medical condition.
Anticonvulsants for Bipolar Disorder
Anticonvulsants seem to act as mood stabilizers and may enhance the action of atypical antipsychotics. They help to even the highs and lows of mood to people suffering from bipolar disorder (manic depression).
At first, they were prescribed only for people who did not respond to lithium. Today, they are often taken alone, with lithium, or with an antipsychotic drug to control mania.
Anticonvulsants used to treat bipolar disorder include 6:
Anticonvulsants for Pain management
Anticonvulsants have been used in pain management since the 1960s. They are effective mainly for neuropathic pain chronic syndromes like trigeminal neuralgia, diabetic neuropathy, and for migraine prophylaxis 2.
Carbamazepine was the first of anticonvulsants to be studied in clinical trials and has been longest in use for neuropathic pain. Clinical trial data support its use in treating trigeminal neuralgia, but data for treatment of painful diabetic neuropathy are less convincing.
Oxcarbazepine is used for trigeminal neuralgia and painful diabetic neuropathy.
Gabapentin is the most widely used anticinvulsant for the treatment of neuropathic pain, specifically for painful diabetic neuropathy and postherpetic neuralgia. This drug also reduces postoperative pain.
Pregabalin is very effective for neuropathic pain and fibromyalgia 7. Pregabalin also has utility in the management of pre-operative and post-operative pain.
Lamotrigine has been reported to be effective in relieving pain from trigeminal neuralgia refractory to other treatments, and central post-stroke pain.
Results from clinical trials of phenytoin are equivocal. Zonisamide's mechanisms of action suggest that it would be effective in controlling neuropathic pain symptoms. Other anticonvulsants, including lorazepam, valproate, topiramate, and tiagabine, have also been under investigation. Anecdotal experience provides support for oxcarbazepine and levetiracetam 4.
Several recent clinical trials have shown that anticonvulsants may reduce spontaneous and movement-evoked pain. Some early findings suggest further that anticonvulsant drugs may alleviate postoperative anxiety, accelerate postoperative functional recovery and reduce chronic postsurgical pain 1.
Anticonvulsants for Migraine
Anticonvulsant drugs seem to be useful for the prophylaxis of migraine. This might be explained by a variety of actions of these drugs in the central nervous system that are probably relevant to the pathophysiology of migraine. Anticonvulsants that have demonstrated their efficacy in clinical trials are divalproex sodium, topiramate, sodium valproate, gabapentin, carbamazepine. Topiramate is the only anticonvulsant approved by the FDA for migraine prophylaxis. Neither clonazepam nor lamotrigine was superior to placebo in the studies. 3
Written by HealthyStock.net, October 2009