Anti-Seizure Meds Flashcards
(63 cards)
Anti-Seizure -
Effectiveness: ___% of seizures can be adequately controlled by pharm therapy.
Development of new drugs is focused on treating ___ cases.
The ideal antiseizure drug prevents/inhibits ____, but does not affect ____.
Most of the medications are more effective on abnormally firing neurons than normal activity.
Antiseizure drugs do not modify or treat ___, they only _____
65-70%
refractory cases.
seizure activity
normal CNS function.
Antiseizure drugs do not modify or treat the cause of epilepsy, they only reduce the manifestations of the disease.
Two mechanism classifications of Anti-Seizure Meds
- Increase Threshold
(increase GABA, decrease Glutamate) - Inhibit Spread
Antiseizure meds PK
Protein binding - can cause drug-drug interactions with other drugs that circulate bound to proteins.
Metabolism – hepatic microsomal enzymes and several induce the synthesis of CYP enzymes (decreased activity). The decreased effectiveness of OCPs due to increased metabolism resulting from antiseizure that induce CYP3A4.
Anti-seizure Meds and Teratogenicity
Infants born to moms w/epilepsy have 2X the risk of congenital malformations than offspring of non-epileptic mothers.
Several antiseizure meds are known to be teratogenic.
Antiseizure drugs that induce CYP enzymes increase the breakdown of Vitamin K in the infant - intracerebral bleeding
Antiseizure Meds Therapeutic Uses
several antiseizure drugs are effective in a broad spectrum of epilepsies.
However, several types of epilepsies (e.g. absence seizures) are effectively treated with only a few selective drugs.
AntiSeizure Meds
Almost all of the anti-seizure meds are effective in partial epilepsy.
Many are effective in generalized epilepsy.
There are some meds used for partial epilepsy that shouldn’t be used in generalized epilepsy because they will worsen the seizures.
Monotherapy vs Combinations
Therapy with a ___ is the preferred treatment of epilepsy.
If a drug is ineffective then …
Combination therapy should be considered only if _____
Combination tx is only effective in a small percentage of pts and the likelihood of ____increases.
If combo therapy is necessary, drugs with _____ should be used.
Therapy with a single drug is the preferred treatment of epilepsy.
If a drug is ineffective then another drug should be substituted.
Combination therapy should be considered only if the second drug is ineffective.
Combination therapy is only effective in a small percentage of patients and the likelihood of side effects increases.
If combination therapy is necessary, drugs with different mechanisms of action should be used.
Phenobarbital
Barbiturate
(all barbiturates have antiseizure activity)
Low toxicity and inexpensive
Phenobarbital
MOA
enhances synaptic inhibition by potentiating the GABA-induced chloride conductance at the GABAA receptor.
Phenobarbital
uses
neonates and infants (less sedation)
Phenobarbital metabolism
CYP2C9
PhB induces CYP2C, CYP3C enzymes in the liver and uridine diphosphate-glucuronosyltransferase (UGT).
Consideration for OCPs
Phenobarbital Toxicity
Sedation = major side effect of PhB
tolerance to the sedation occurs with chronic admin.
high doses - nystagmus and ataxia.
KIDS - irritability and agitation
elderly - confusion.
continuous infusion - induce coma
Benzos
All benzos have antiseizure activity
abort seizures
Benzo MOA
Enhance GABA-induced activity of GABAA
Benzo Uses
aborting seizures, especially status epilepticus.
Benzos used for antiseizure tx have rapid onset and short duration of action.
Lorazepam (Ativan)
Benzo
Status epilepticus
Commonly used in ER - quick onset when given I.V. (10 min)
Midazolam (Versed)
Benzo
Status epilepticus
IV Drip
Clonazepam (Klonopin)
Benzo
PO
Prolonged Seizures
Diazepam (Valium)
Benzo
rectal, PO
Seizure clusters
status epilepticus
Benzo: ____ formulation is used in children
Rectal
Clobazam (Onfi)
benzo
maintenance therapy
Benzo Side Effects
Drowsiness and lethargy, sedation and addiction.
Tolerance limits long term use of the drugs.
Sudden discontinuation can cause seizures.
At resting potential (-70 mV) voltage-gated channels are in the ____ state. Depolarization of the membrane to threshold (-55 mV) activates the channels and _____. After a brief time (1 msec), the channel moves to ____ and no Na+ can pass through the channel.
closed state
causes them to move to the open state
inactive state
Antiseizure - Voltage-Gated Sodium Channels
During the inactive state, the channels cannot be opened. The _____ is the time it takes the channels to go from the inactive state to the resting state.
The absolute refractory period
