Anticonvulsant Medications
Anticonvulsant Medications ( 6 Questions)
A nurse is preparing to administer phenobarbital to a client who has status epilepticus. The nurse should be aware that phenobarbital has which of the following mechanisms of action?
Choice A is wrong because phenobarbital does not inhibit carbonic anhydrase in the brain. Carbonic anhydrase is an enzyme that catalyzes the reversible reaction of carbon dioxide and water to form bicarbonate and protons. Inhibiting carbonic anhydrase can reduce the production of cerebrospinal fluid, but it does not prevent seizures. In fact, some carbonic anhydrase inhibitors, such as acetazolamide, are used as anticonvulsants for certain types of seizures⁵.
Choice B is wrong because phenobarbital does not inhibit GABA transaminase in the brain. GABA transaminase is an enzyme that degrades GABA into succinic semialdehyde and glutamate. Inhibiting GABA transaminase can increase the availability of GABA and prevent seizures. Some anticonvulsants, such as vigabatrin, work by this mechanism⁵.
Phenobarbital is a barbiturate that acts as an allosteric modulator of GABA A receptors, which are ligand-gated chloride channels that mediate inhibitory neurotransmission³. By increasing the duration of opening of the chloride channels, phenobarbital hyperpolarizes the neuronal membrane and reduces its excitability⁴.
Choice D is wrong because phenobarbital does not enhance the binding of glutamate to its receptors in the brain. Glutamate is the major excitatory neurotransmitter in the brain and binds to various types of receptors, such as NMDA, AMPA, and kainate receptors. Enhancing the binding of glutamate to its receptors would increase the depolarization and excitability of neurons and trigger seizures. Some anticonvulsants, such as felbamate and topiramate, work by blocking glutamate receptors⁵.