Disorder of brain function characterized by the periodic and unpredictable occurrences of seizures
Epilepsy
What is epilepsy characterized by?
Periodic and unpredictable occurrence of seizures
Transient alteration of behaviors due to excessive discharge of population of brain neurons
Seizure
Two types of epilepsy
Partial/focal
Generalized
Partial/focal epilepsy has neuronal discharge onset in what part of the brain
Localized area of the cerebral cortex, beginning in only one hemisphere of the brain
In generalized epilepsy, neuronal discharge is _____ at the onset
Widespread
Where in the brain does generalized epilepsy begin?
Both hemispheres of the brain
Seizures where consciousness is preserved
Simple partial seizures
Seizure greater than 5 minutes, needing medication
Status epilepticus
Seizures where consciousness is impaired and preceded by psychological symptoms
Complex partial seizures
3 types of generalized seizures
Tonic-clonic
Absence
Myoclonic
First phase of tonic-clonic seizures
Tonic phase (less than 1 minute) = sudden loss of consciousness, muscle rigidity, and respiration arrest
Second phase of tonic-clonic seizures
Clonic phase (2-3 minutes) - jerking of body muscles, with lip or tongue biting, and focal and urinary incontinence (relaxation and contraction)
Seizures with impaired consciousness (sudden onset and abrupt cessation duration < 10 seconds)
Absence seizures
What ages usually have absence seizures
Childhood, usually cease by age 20 yrs
Seizures with single or multiple myoclonic muscle jerks (to a greater or lesser extent, in a wide variety of seizures) no loss of consciousness
Myoclonic seizures
What happens to the neurons in epilepsy?
During a seizure, a small number of hyperexcitable neurons fire abnormally in synchrony
Normal membrane conductances
Inhibitory synaptic currents break down
Mechanism of epilepsy
Alteration in number, type and biophysical properties of voltage or ligand-gated K, Na, or Ca ion channels in neuronal membranes
What happens to the GABA(a) receptors in epilepsy?
Breakdown of GABA(a) receptor mediates an increase in chloride ion conductance and inhibition of action potentials
Synaptic excitation in epilepsy is mediated by what?
Ionotropic glutamate receptors
Na channel modulator drugs for epilepsy that enhance the fast inactivation
Phenytoin, carbamazepine, valproate (Mixed MOA)
Na channel modulator drugs for epilepsy that enhance slow inactivation
Lacosamide
Calcium channel blocker (T-type) drug for epilepsy
Ethosuximide
Calcium channel modulator (alpha2gama ligands) drug for epilepsy
Gabapentin
GABA-enhancing drug for epilepsy
Diazepam
Glutamate receptor antagonist drug for epilepsy
Perampanel
MOA for sodium channel modulators that enhance fast inactivation in epilepsy
Decreasing sodium influx into neurons by prolonging the existence of the inactivated state
How do you take phenytoin?
Intravenous use only fosphenytoin (water soluble prodrugs)
Phenytoin is metabolized by what?
CYP2C9; metabolism is nonlinear; elimination kinetics shift from first-order to zero-order at moderate to high dose lovels
How are phenytoin plasma levels increased?
Transiently by drugs that compete for binding (carbamazepine, sulfonamides, valproic acid)
What does phenytoin do to the metabolism of other drugs?
Increases the metabolism of other drugs, leading to decreases of their actions (contraceptives - can lead to pregnancy)
Side effects of phenytoin
Gingival hyperplasia (gums grow over teeth)
Coarsening of facial features
Decreased bone density due to increased vitamin D metabolism
Cardiac arrhythmias
How should you treat patients who are taking phenytoin?
Consistency treated with the same drugs from a single manufacturer. However, if switch to other product, care must be taken to select a therapeutically equivalent product.
Sodium channel modulator for enhancing fast inactivation that has hepatic CYP3A4, which is responsible for its metabolism
Carbamazepine
Carbamazepine has what for it’s active metabolite?
10,11 epoxied
Adverse effects of carbamazepine
Stupor, coma, and respiratory depression
Blurred vision
Sodium channel modulator for enhancing fast inactivation that is a broad spectrum ASD (anti-seizure drug)
Valproate
MOA for valproate
Increase inactivated state of sodium channels at different sites than phenytoin or carbamazepine
Produces small reductions of low-threshold (T) calcium currents in thalamic neurons
Increases GABA concentration (Inactivating GABA-T transaminase)
Adverse effects of valproate
Elevated hepatic enzymes (hepatitis, especially in children < 2 years old)
Sodium channel modulator for enhancing slow inactivation that is used to limit sustained repetitive firing
Lacosamide
Adverse effects of lacosamide
Double vision
Among all ASD, lacosamide may contribute to suicidal ideation. The FDA has mandate a black-bock warning for this agents
Calcium channel blocker (T-type) that is the drug of choice for the treatment of absence seizures
Ethosuximide
MOA for ethosuximide
Reduces low threshold T-type calcium currents in thalamic neurons; inhibits absence seizures
Adverse effects of ethosuximide
Nausea
Vomiting
Anorexia
Photophobia
Calcium channel modulators (alpha2gama ligands) that are designed as GABA agonists
Gabapentin
MOA for gabapentin
GABA agonist
Bin with high affinity to alpha2gama subunit of calcium channels, resulting in decreasing calcium entry
Adverse effects of gabapentin
No significant drug interaction which makes it idea to be used with other ASD’s
GABA-receptor enhancing drug for epilepsy that increase the frequency, but not duration of opening at GABA activated chloride channels
Diazepam
Therapeutic use for diazepam
In therapy of absence seizures and myoclonic seizures in children
What is diazepam an effective agent for?
Status epilepticus
What is status epilepticus?
A dangerous condition in which epileptic seizures follow one another without recovery of consciousness between them)
Treated with diazepam
GABA-receptor enhancing drug that increases the duration of bursts of GABA(a) receptors on chloride channels without changing the frequency of the burst
Phenobarbital
Adverse effects of phenobarbital
Sedation
Ataxia
Vertigo
Morbilliform rash in sensitive individuals (rash on back)
Glutamate receptor antagonist that is metabolized by hepatic CYP3A, possibly decreasing the effectiveness of hormonal contraceptives, carbamazepine.
Perampanel
MOA for perampanel
Selective, non competitive antagonist of the AMPA-type ionotropic glutamate receptor
AMPA receptor antagonists prevent repetitive neuronal firing
Adverse effects of perampanel
Anxiety
Double vision
Commonly used drugs for focal/partial seizures
Carbamazepine
Phenytoin
(Also phenobarbital, topiramate, and valproic acid)
Commonly used drugs for generalized tonic-clonic (grand mal) seizures
Carbamazepine
Phenytoin
Valproic acid
(Alternative agent in adults = phenobarbital)
Commonly used drugs for generalized absence seizures
Ethosuximide (DOC)
Valproic acid
Ethosuximide is the preferred drug for what type of seizure because it causes minimal sedation
Generalized absence seizures
DOC for myoclonic seizures
Valproic acid
DOC for status epilepticus
IV diazepam