Zonisamide as a treatment for partial epileptic seizures: a systematic review

Glycine Receptors in Spinal Nociceptive Control-An Update

Diminished inhibitory control of spinal nociception is one of the major culprits of chronic pain states. Restoring proper synaptic inhibition is a well-established rational therapeutic approach explored by several pharmaceutical companies. A particular challenge arises from the need for site-specific intervention to avoid deleterious side effects such as sedation, addiction, or impaired motor control, which would arise from wide-range facilitation of inhibition. Specific targeting of glycinergic inhibition, which dominates in the spinal cord and parts of the hindbrain, may help reduce these side effects. Selective targeting of the α3 subtype of glycine receptors (GlyRs), which is highly enriched in the superficial layers of the spinal dorsal horn, a key site of nociceptive processing, may help to further narrow down pharmacological intervention on the nociceptive system and increase tolerability. This review provides an update on the physiological properties and functions of α3 subtype GlyRs and on the present state of related drug discovery programs.

The efficacy of lacosamide as monotherapy and adjunctive therapy in focal epilepsy and its use in status epilepticus: clinical trial evidence and experience

Lacosamide (LCM) is approved for anticonvulsive treatment in focal epilepsy and exhibits its function through the slow inactivation of voltage-gated sodium channels (VGSCs). LCM shows comparable efficacy with other antiepileptic drugs (AEDs) licensed in the last decade: in three randomized placebo-controlled trials, significant median seizure reduction rates of 35.2% for 200 mg/day, 36.4-39% for 400 mg/day and 37.8-40% for 600 mg/day were reported. Likewise, 50% responder rates were 38.3-41.1% for 400 mg/day and 38.1-41.2% for 600 mg/day. Similar rates were reported in post-marketing studies. The main adverse events (AEs) are dizziness, abnormal vision, diplopia and ataxia. Overall, LCM is well tolerated and has no clinically-relevant drug-drug interactions. Due to the drug's intravenous availability, its use in status epilepticus (SE) is increasing, and the available data are promising.

Synergism of perampanel and zonisamide in the rat amygdala kindling model of temporal lobe epilepsy

OBJECTIVE

Anticonvulsive monotherapy fails to be effective in one third of patients with epilepsy resulting in the need for polytherapy regimens. However, with the still limited knowledge, drug choices for polytherapy remain empirical. Here we report experimental data from a chronic epilepsy model for the combination of perampanel and zonisamide, which can render guidance for clinical studies and individual drug choices.

METHODS

The anticonvulsant effects of the combination of perampanel and zonisamide were evaluated in a rat amygdala kindling model. Furthermore, the potential for motor impairment was evaluated. The type of interaction was quantitatively assessed based on isobolographic analysis.

RESULTS

When administered alone, zonisamide dose-dependently increased the afterdischarge threshold in fully kindled rats. Moreover, data confirmed efficacy of perampanel to inhibit seizure initiation and progression with an impact on propagation of activity from the focus. Pronounced threshold increases were observed following administration of a constant zonisamide dosage combined with different doses of perampanel. Isobolographic analysis of drug responses, which is based on individual drug dose-effect data, revealed a synergistic interaction substantiating the high efficacy of the combination. Furthermore, rotarod data indicated that the combination has a favorable tolerability profile when zonisamide is coadministered with low doses of perampanel. Plasma concentration analysis argued against a pharmacokinetic interaction as a basis for the synergism.

SIGNIFICANCE

The findings clearly indicate a pronounced synergistic anticonvulsant effect for the combination of the noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist perampanel with zonisamide, which modulates voltage-sensitive sodium channels and T-type calcium currents. Consequently, polytherapy using these two antiepileptic drugs might be efficacious for clinical management of partial-onset seizures. The findings indicate that the impact of dose ratios on tolerability needs be taken into account. With regard to conclusions about the extent of the synergism and its implications further antiepileptic drug combinations need to be evaluated allowing direct comparison.