Vigabatrin is an anticonvulsant chemically unrelated to other anticonvulsants. Vigabatrin prevents the catabolism of GABA by irreversibly inhibiting the enzyme GABA transaminase. It is an analog of GABA, but it is not a receptor agonist. However, vigabatrin is not a potent inhibitor of GABA-T with a Ki of 10 mM. Vigabatrin increases brain concentrations of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the CNS, by irreversibly inhibiting enzymes that catabolize GABA (gamma-aminobutyric acid transaminase, GABA-T). Duration of action is determined by rate of GABA-T re-synthesis. Vigabatrin may also work by suppressing repetitive neuronal firing through inhibition of voltage-sensitive sodium channels. Although administered as a racemic mixture, only the S(+) enantiomer is pharmacologically active. Vigabatrin is sold under the trade name SABRIL, it is indicated as adjunctive therapy for adults and pediatric patients 10 years of age and older with refractory complex partial seizures who have inadequately responded to several alternative treatments and for whom the potential benefits outweigh the risk of vision loss.

Lacosamide is an anticonvulsant that is FDA approved for the treatment of partial-onset seizures. The precise mechanism by which lacosamide exerts its antiepileptic effects in humans remains to be fully elucidated. In vitro electrophysiological studies have shown that lacosamide selectively enhances slow inactivation of voltage-gated sodium channels, resulting in stabilization of hyperexcitable neuronal membranes and inhibition of repetitive neuronal firing Common adverse reactions include diplopia, headache, dizziness, nausea. Patients with renal or hepatic impairment who are taking strong inhibitors of CYP3A4 and CYP2C9 may have a significant increase in exposure to Lacosamide tablets.

Zonisamide is an antiseizure drug chemically classified as a sulfonamide and unrelated to other antiseizure agents. The precise mechanism by which zonisamide exerts its antiseizure effect is unknown, although it is believed that the drug blocks sodium and calcium channels, which leads to the suppression of neuronal hypersynchronization (i.e. convulsions). Sonisamide has also been found to potentiate dopaminergic and serotonergic neurotransmission but does not appear to potentiate syanptic activity by GABA (gamma amino butyric acid). Zonisamide binds to sodium channels and voltage sensitive calcium channels, which suppresses neuronal depolarization and hypersynchronization. Zonisamide also inhibits carbonic anhydrase to a weaker extent, but such an effect is not thought to contribute substantially to the drug's anticonvulsant activity. Zonisamide is approved in the United States, United Kingdom, and Australia for adjunctive treatment of partial seizures in adults and in Japan for both adjunctive and monotherapy for partial seizures (simple, complex, secondarily generalized), generalized (tonic, tonic-clonic (grand mal), and atypical absence) and combined seizures.

Levetiracetam is an anticonvulsant medication used to treat epilepsy. Levetiracetam may selectively prevent hypersynchronization of epileptiform burst firing and propagation of seizure activity. The precise mechanism(s) by which levetiracetam exerts its antiepileptic effect is unknown. The antiepileptic activity of levetiracetam was assessed in a number of animal models of epileptic seizures. Levetiracetam did not inhibit single seizures induced by maximal stimulation with electrical current or different chemoconvulsants and showed only minimal activity in submaximal stimulation and in threshold tests. Levetiracetam also displayed inhibitory properties in the kindling model in rats, another model of human complex partial seizures, both during kindling development and in the fully kindled state. The predictive value of these animal models for specific types of human epilepsy is uncertain. In vitro and in vivo recordings of epileptiform activity from the hippocampus have shown that levetiracetam inhibits burst firing without affecting normal neuronal excitability, suggesting that levetiracetam may selectively prevent hypersynchronization of epileptiform burst firing and propagation of seizure activity. Levetiracetam at concentrations of up to 10 µM did not demonstrate binding affinity for a variety of known receptors, such as those associated with benzodiazepines, GABA (gamma-aminobutyric acid), glycine, NMDA (Nmethyl-D-aspartate), re-uptake sites, and second messenger systems. Furthermore, in vitro studies have failed to find an effect of levetiracetam on neuronal voltage-gated sodium or T-type calcium currents and levetiracetam does not appear to directly facilitate GABAergic neurotransmission. However, in vitro studies have demonstrated that levetiracetam opposes the activity of negative modulators of GABA- and glycine-gated currents and partially inhibits N-type calcium currents in neuronal cells. A saturable and stereoselective neuronal binding site in rat brain tissue has been described for levetiracetam. Experimental data indicate that this binding site is the synaptic vesicle protein SV2A, thought to be involved in the regulation of vesicle exocytosis. Interaction of levetiracetam with the SV2A protein may contribute to the antiepileptic mechanism of action of the drug. Levetiracetam, along with other anti-epileptic drugs, can increase the risk of suicide behavior or thoughts. People taking levetiracetam should be monitored closely for signs of worsening depression, suicidal thoughts or tendencies, or any altered emotional or behavioral states.

Tiagabine (trade name Gabitril) is an anticonvulsant medication used in the treatment of Partial Seizures. The precise mechanism by which Tiagabine exerts its antiseizure effect is unknown, although it is believed to be related to its ability to enhance the activity of gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Tiagabine binds to recognition sites associated with the GABA uptake carrier. It is thought that, by this action, Tiagabine blocks GABA uptake into presynaptic neurons, permitting more GABA to be available for receptor binding on the surfaces of post-synaptic cells. Tiagabine is approved by U.S. Food and Drug Administration (FDA) as an adjunctive treatment for partial seizures in individuals of age 12 and up. It may also be prescribed off-label by physicians to treat anxiety disorders and panic disorder as well as neuropathic pain (including fibromyalgia). For anxiety and neuropathic pain, tiagabine is used primarily to augment other treatments. Tiagabine may be used alongside selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, or benzodiazepines for anxiety, or antidepressants, gabapentin, other anticonvulsants, or opioids for neuropathic pain. The most common side effect of tiagabine is dizziness. Other side effects that have been observed with a rate of statistical significance relative to placebo include asthenia, somnolence, nervousness, memory impairment, tremor, headache, diarrhea, and depression.

Felbamate is an antiepileptic indicated as monotherapy or as an adjunct to other anticonvulsants for the treatment of partial seizures resulting from epilepsy. Receptor-binding studies in vitro indicate that felbamate has weak inhibitory effects on GABA-receptor binding, benzodiazepine receptor binding, and is devoid of activity at the MK-801 receptor binding site of the NMDA receptor-ionophore complex. However, felbamate does interact as an antagonist at the strychnine-insensitive glycine recognition site of the NMDA receptor-ionophore complex. The mechanism by which felbamate exerts its anticonvulsant activity is unknown, but in animal test systems designed to detect anticonvulsant activity, felbamate has properties in common with other marketed anticonvulsants. In vitro receptor binding studies suggest that felbamate may be an antagonist at the strychnine-insensitive glycine-recognition site of the N-methyl-D-aspartate (NMDA) receptor-ionophore complex. Antagonism of the NMDA receptor glycine binding site may block the effects of the excitatory amino acids and suppress seizure activity. Animal studies indicate that felbamate may increase the seizure threshold and may decrease seizure spread. It is also indicated that felbamate has weak inhibitory effects on GABA-receptor binding, benzodiazepine receptor binding. Felbamate should be used only in those patients who respond inadequately to alternative treatments and whose epilepsy is so severe that a substantial risk of aplastic anemia and/or liver failure is deemed acceptable in light of the benefits conferred by its use. Felbatol is the brand name used in the United States for felbamate.

Valproic acid (VPA; valproate; di-n-propylacetic acid, DPA; 2-propylpentanoic acid, or 2-propylvaleric acid) was first synthesized in 1882, by Burton. FDA approved valproic acid for the treatment of manic episodes associated with bipolar disorder, for the monotherapy and adjunctive therapy of complex partial seizures and simple and complex absence seizures and adjunctive therapy in patients with multiple seizure types that include absence seizures and for the prophylaxis of migraine headaches. The mechanisms of VPA which seem to be of clinical importance in the treatment of epilepsy include increased gamma-aminobutyric acid (GABA)-ergic activity, reduction in excitatory neurotransmission, and modification of monoamines. Recently, it was discovered that the VPA is a class I selective histone deacetylase inhibitor. This activity can be distinguished from its therapeutically exploited antiepileptic activity.

Ethosuximide is a succinimide anticonvulsant, used in the treatment of epilepsy. Ethosuximide suppresses the paroxysmal three cycle per second spike and wave activity associated with lapses of consciousness which is common in absence (petit mal) seizures. The frequency of epileptiform attacks is reduced, apparently by depression of the motor cortex and elevation of the threshold of the central nervous system to convulsive stimuli. Binds to T-type voltage sensitive calcium channels. Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. The isoform alpha-1G gives rise to T-type calcium currents. T-type calcium channels belong to the "low-voltage activated (LVA)" group and are strongly blocked by mibefradil. A particularity of this type of channels is an opening at quite negative potentials and a voltage-dependent inactivation. T-type channels serve pacemaking functions in both central neurons and cardiac nodal cells and support calcium signaling in secretory cells and vascular smooth muscle. They may also be involved in the modulation of firing patterns of neurons which is important for information processing as well as in cell growth processes. Ethosuximide is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.

Lithium is an alkali metal widely used in industry. Lithium salts are indicated in the treatment of manic episodes of Bipolar Disorder. The use of lithium in psychiatry goes back to the mid-19th century. Early work, however, was soon forgotten, and John Cade is credited with reintroducing lithium to psychiatry for mania in 1949. Mogens Schou undertook a randomly controlled trial for mania in 1954, and in the course of that study became curious about lithium as a prophylactic for depressive illness. In 1970, the United States became the 50th country to admit lithium to the marketplace. The specific mechanisms by which lithium exerts its mood-stabilizing effects are not well understood. Lithium appears to preserve or increase the volume of brain structures involved in emotional regulation such as the prefrontal cortex, hippocampus and amygdala, possibly reflecting its neuroprotective effects. At a neuronal level, lithium reduces excitatory (dopamine and glutamate) but increases inhibitory (GABA) neurotransmission; however, these broad effects are underpinned by complex neurotransmitter systems that strive to achieve homeostasis by way of compensatory changes. For example, at an intracellular and molecular level, lithium targets second-messenger systems that further modulate neurotransmission. For instance, the effects of lithium on the adenyl cyclase and phospho-inositide pathways, as well as protein kinase C, may serve to dampen excessive excitatory neurotransmission. In addition to these many putative mechanisms, it has also been proposed that the neuroprotective effects of lithium are key to its therapeutic actions. In this regard, lithium has been shown to reduce the oxidative stress that occurs with multiple episodes of mania and depression. Further, it increases protective proteins such as brain-derived neurotrophic factor and B-cell lymphoma 2, and reduces apoptotic processes through inhibition of glycogen synthase kinase 3 and autophagy.

Ethotoin is a hydantoin derivative and anticonvulsant. Ethotoin exerts an antiepileptic effect without causing general central nervous system depression. The mechanism of action is probably very similar to that of phenytoin. The latter drug appears to stabilize rather than to raise the normal seizure threshold, and to prevent the spread of seizure activity rather than to abolish the primary focus of seizure discharges. Ethotoin inhibits nerve impulses in the motor cortex by lowering sodium ion influx, limiting tetanic stimulation. Ethotoin is used for the control of tonic-clonic (grand mal) and complex partial (psychomotor) seizures. Ethotoin is marketed as Peganone by Ovation.