Antiepiletics Test 1 Flashcards
Collective term used to designate a group of chronic CNS disorders characterized by the onset of sudden disturbances of sensory, motor, autonomic, or psychic origin.
EPILEPSY
Epilepsy generally transient with the exception of _____ ________.
status epilepticus
Protein binding greatly varies: _______0% to ______> 90%
gabapentin, phenytoin
GI absorption is _____ over hours and may be incomplete (ESPECIALLY gabapentin)
slow
Medications relying on renal excretion and may need adjusting according to renal function: (5)
Remaining drugs should be dosed according to patient’s liver dysfunction
Gabapentin Pregabalin Levetitracetam Vigabatrin Zonisamide
Drug clearance and Elimination half-time range from:
Hours: (4 drugs)
TO
Days: (4 drugs)
carbamazepine, valproate, primidone, gabapentin
to
phenytoin, lamotrigine, phenobarbital, zonisamide
Because of their ability to induce or inhibit drug metabolism ALL antiepileptic drugs may be associated with drug interactions resulting interactions of plasma drug concentrations EXCEPT
Gabapentin
Levetiracetam
vigabatrin
Examples of highly bound protein drugs:
Phenytoin
Valproate
Carbamazepine
________ is principle binding protein for antiepileptic drugs
Albumin
Medication ineffectiveness is failure to achieve sufficient ___________.
high plasma concentrations
Noncompliance is high in _______ and _______.
elderly and adolescents
Dosing at ½ the drug’s elimination half-time ensures :
that a single dose missed will not result in sub-therapeutic plasma concentrations
Carbamazepine dosing
10-40 mg/kg/day in 2-3 doses
Gabapentin dosing
10-60mg/kg/day
Phenobarbital dosing
2-5mg/kg/day could divide x2 a day
Phenytoin dosing
3-7mg/kg/day divided x3
Toprimate dosing
500-3000mg/day in 2-4 doses.
Valproate dosing
500-3000mg/day in 2-4 doses.
_______ is the ONLY agent requiring routine monitoring
Phenytoin
_______ seizure activity has a localized or focal origin in most patients.
Epileptic
________ and ________ firing in a seizure focus is usually unknown.
High frequency and synchronous
Factors that my facilitate the spread of a seizure focus into areas of the normal brain:
Blood glucose concentrations PaO2 PaCO2 pH Endocrine function Stress fatigue Electrolyte balance
Neurons of chronic seizure focus exhibit a type of _______ ______ with regard to excitatory stimuli
denervation hypersensitivity
If the spread of a seizure focus is extensive enough the entire brain is activated and a ______ ______seizure with unconsciousness ensues
tonic-clonic
Once a seizure is initiated it is likely to be maintained by reentry of _____ _____ in a _____ ____ _____ that my not even include the original seizure focus.
excitatory impulses, closed feedback pathway
Controls muscle movements, thinking, and judgment.
Frontal lobe-
Controls sense of touch, response to pain and temperature, and understanding of language.
Parietal lobe-
Controls vision.
Occipital lobe-
Controls hearing and memory
Temporal lobe-
Controls balance.
Cerebellum
Controls breathing and regulates heartbeat.
Brain stem-
Drugs that delay reactivation of sodium channels during high frequency neuronal firing produce an inhibitory effect on creation of action potentials until neuronal discharge is blocked:
Phenytoin Carbamazepine Primidone Valproate lamotrigine
Some drugs act at both sodium and calcium ion channels:
Phenytoin
Carbamazepine
Valproate
Lamotrigine
Other drugs act selectively on calcium ion channels:
Ethosuximide: Selectively blocks the T-type calcium ion current which is thought to act as a pacemaker for the thalamic neurons and may be important in absence seizures
Phenobarbital
Those drugs that alter synaptic function act primarily by enhancing GABA mediated neuronal inhibition:
Phenobarbital: And other Barbiturates increase the duration of ion channel openings
Benzodiazepines: increase frequency of GABA-mediated ion channel openings.
______ delays the reuptake of GABA from synaptic clefts, effectively enhancing GABA-mediated neuronal inhibition after synaptic release of the neurotransmitter.
Tiagabine
MOA and targeted seizures of Cabamazepine
Sodium channel blockade, Partial seizures
MOA and targeted seizures of Gabapentin
Unknown (decrease gaba release), Partial and generalized seizures
MOA and targeted seizures of Phenobarbital
Chloride ion channels, Partial and generalized seizures
MOA and targeted seizures of Phenytoin
Sodium ion channels blockade, Calcium ion channel, NMDA receptors.
Partial and generalized seizures
MOA and targeted seizures of Toprimate
Sodium ion channels blockade, enhanced GABA activity, Glutamate antagonism, Calcium ion channel blocker
Partial and generalized seizures
MOA and targeted seizures of Valproate
Sodium ion channels blockade, Calcium ion channel
Partial and generalized seizures
Recent benzo derivative. Unique because it does not cause significant sedation and can be used long-term d/t tolerance is relatively uncommon
Clobazam
reserved for selected patients with uncontrolled seizures d/t its side effects
Felbamate
patients develop a tolerance and sedation is a common side effects
Clonazepam
Drugs used for partial seizures and has acceptable side effect profiles
Carbamazepine Lamotrigine Oxcarbazepine Topiramate Zonisamide phenytoin
Drugs useful for treatment of generalized seizures:
Valproate
Lamotrigine
Topiramate
Drugs effective in treatment of generalized nonconvulsive seizures and especially absence seizures
Ethosuximide
Lamotrigine
valproate
Gabapentin MOA
Is an analog of GABA that increases synaptic GABA
Gabapentin therapeutic dose
2- 20 mcg/mL
Gabapentin elimination
Zero protein bound. Renal elimination
Antiepileptic drugs can render PO birth control _____ effective
less
Seizures during pregnancy = _______ morbidity and mortality for mother and fetus
increased
for maternal epilepsy Goal:
Monotherapy with lowest dose to stop seizures
Significant teratogenicity can happen if meds give in first____weeks
8
________ and _______x2 risk of Neural tube defects such as spina bifida in preg women
Valproate and carbamazepine
seizure medication for preg women
Lamotrigine
Seizure medication for preg woman that can be added especially during labor.
Clobazam
Used for patients with nonconvulsive and convulsive partial seizures. Useful in:
Trigeminal neuralgia
Glossopharyngeal neuralgia
CARBAMAZEPINE
CARBAMAZEPINE _____ protein bound
70-80%
CARBAMAZEPINE rapid absorption peak plasma concentrations in ____hours
2-6
CARBAMAZEPINE Plasma elimination half time is ____hours
8-24
CARBAMAZEPINE usual side effects
sedation, vertigo, diplopia, n/v and chronic diarrhea in some patients.
Carbamazepine Rare side effects but can be life threatening:
SIADH Aplastic anemia Thrombocytopenia Hepatocellular and cholestatic jaundice Oliguria HPTN Cardiac dysrhythmias WBC suppression
Carbamazepine High plasma concentration can have a arginine vasopressin hormone like actions resulting in _________.
hyponatremia
Carbamazepine Accelerates metabolism of:
Valproic acid Ehtosuximide Corticosteroids Anticoagulants Antipsychotics
Carbamazepine Drugs that inhibit metabolism of carbamazepine sufficiently to cause toxic effects:
Cimetidine Propoxyphene Diltiazem Verapamil Isoniazid erythromycin
Felbamate Pharmacokinetics:
Rapid PO absorption
Prolonged elimination half time
Excreted unchanged by kidneys
Felbamet side effects
Hepatotoxicity
Monitor CPC, Liver Functions indicated
Metabolized by liver cytochrome P 450 so effected by concurrent meds metabolized by cytochrome P 450
Concomitant administration of carbamazepine or phenytoin may decrease plasma concentrations of Felbamate
Since Felbamate is a potent inhibitor of P 450 enzymes, it can slow metabolism of phenytoin, phenobarbital and Valproic acid
If receiving Felbamate, carbamazepine, phenytoin, and Valproic, dose should be decreased by 20-30% to prevent toxicity
PHENOBARBITAL _____ acting
long
PHENOBARBITAL Effective against ALL seizure types EXCEPT _______________.
nonconvulsive primary generalized seizures
PHENOBARBITAL Second-line drug treatment due to its side effects:
Cognitive
Behavioral
PHENOBARBITAL peak concentration
12-18 hours
Phenobarbital Plasma protein binding is
48% to 54%
Phenobarbital Principle metabolite is an _______ parahydroxyphenyl derivative excreted in urine as a sulfate conjugate.
inactive
Phenobarbital Plasma concentration of ________ are usually necessary for seizure control
10-40 mcg/ml
Phenobarbital side effects
Sedation, irritability, hyperactivity most troublesome side effects
Tolerance to sedation with chronic therapy
Depression in adults, and confusion in elderly
Megaloblastic anemia that responds to folic acid
Osteomalacia that responds to vitamin D
Nystagmus and ataxia with concentrations > 40 mcg/ml
Abnormal collagen deposition causing Dupuytren (du-pew-TRNAZ) contracture may occur (mainly ring and pinky)
Classic example of a hepatic microsomal enzyme inducer that can accelerate the metabolism of many lipid soluble drugs.
Prototype of hydantoins
PHENYTOIN
Phenytoin can be given acutely to achieve effective plasma concentrations within _____________
20 minutes
Phenytoin Initial adult dose is________. Dose >______rarely tolerated
3-4 mg/kg. Does >500 mg
Phenytoin IV should not exceed ________in adults
Should not exceed____________ (or 50 mg/min) whichever is slower in pediatrics
50 mg/min ,1-3 mg/kg
Phenytoin____% to albumin
90
_________ and ______are likely with concentrations of >20 mcg/ml (Phenytoin)
Nystagmus and ataxia
(Phenytoin) For control of digitalis-induced cardiac dysrhythmias _________ IV is given every 15-30 minutes until a satisfactory response or a max dose of 15 mg/kg is given
0.5-1.0 mg/kg
Phenytoin side effects
CNS toxicity manifesting as: (> 20 mcg/ml)
Nystagmus
Ataxia
Diplopia
Vertigo (cerebellar-vestibular dysfunction
Peripheral neuropathy in 30% of pts
Gingival hyperplasia in 20% pts and is probably the most common manifestation
Valproic Acid is Effective in the treatment of ___________ epilepsies and __________.
all primary generalized and all convulsive epilepsies
Valproic Acid Peak plasma concentrations in _____ hours
1-4
Valproic Acid Plasma protein binding is ____
> 80%
Valproic Acid Elimination half time is ____ hours
7-17
Valproic Acid side effects
Anorexia n/v
Weight gain is common
Fine distal tremor with higher doses
Thrombocytopenia seen frequently at higher doses
Most serious side effect is hepatotoxicity occurring in ~ 0.2% of children under 2 years old who are treated chronically. This is potential fatal. Hepatic necrosis decreases dramatically after 2 years of age
20% treated pts have hyperammonemia without hepatic damage
Sedation and ataxia are INFREQUENT side effects.
Partly eliminated as a ketone containing metabolite, may have false positive results
Can displace phenytoin and diazepam from protein binding sites resulting in increased pharmacologic effects produced by displaced drug
Enzyme inhibitor and may slow metabolism of phenytoin
Causes plasma concentration of phenobarbital to increase ~ 50%
DOES NOT INTERFERE with action of oral contraceptives