Chapter 3 CNS - anticonvulsants + general anesthetics Flashcards
principles of anticonvulsant
- follow serum drug levels
- 2nd drug can be added if maximal dose of 1st is reached (the inital drug should be then tapered and discontinued)
- abrupt d/c of anticonvulsant can induce status epilepticus (always tape doses)
- inform female pt of association w/ birth defects
general anesthetics
- theories suggest anesthetics work by altering lpids in cell membrane stem
measure of potency is minimum alveolar concentration (MAC)
* or concentration of anesthetic that causes immobility in 50% of subjects exposed to agent at one atmosphere
1) halothane - 0.75
2) enflurane - 1.68
3) isoflurane 1.15
4) nitrious oxide - 105.0
Diazepam (valium)
lorazepam (ativan)
indication
* status epilepticus
* rapid onset for stopping active sz
* NOT FOR chronic sz control
effects
drowsiness
clouded mind
ataxia
CNS depression
IV/PO/PR
MANY drugs inhibit metabolism of diazepam
clonazepam (klonopin)
clorazepate (tranxene)
- absence sz; alternative to ethosuximide or valproic acid
effects
drowsiness
clouded mind
ataxia
CNS depression
PO
additive w/ CNS
tiagabine (gabitril)
- blocks presynaptic GABA-uptake
indication
* partial seizure
effects
1) dizziness
2) nervousness
3) tremor
4) fatigue/weakness
5) confusion
PO titrate dose over 6-20 weeks until effective
clear faster in pts taking other anticonvulsants
phenytoin (dilatin)
fosphenytoin (cerebyx)
- reduces Na+, Ca++, K+ currents across neuronal membranes
indication
* all sz except absence
effects
* nystagmus (vision condition in which the eyes make repetitive, uncontrolled movements)
* ataxia
* CNS disturb
* bone marrow suppression
* gingival hyperplasia (excessive gum growth){
* hepatotoxic
* GI disturbances
IV — CNS depression, severe hypotension, arrhythmias, hyperkinesis
PO/IV/IM
serum level 10-20 mcg/ml
metabolized in liver; long half life
carbamazepine (tegretol)
oxcarbazepine (tripleptal)
eslicarbazepine (apitom)
- similar to phenytoin (na+, ca++, k+ stopped those currents)
- antidiuretic effect
- SIMILAR structure to TCA
indication
* all sz except absence
* trigeminal neuralgia (type of chronic pain disorder that involves sudden, severe facial pain)
* manic depression
* schizo when fail to respond to antipsychotics
effects
* agranulocytosis (absolute neutrophil count (ANC) is less than 100 neutrophils per microlitre of blood)
* aplastic anemia (bone marrow cannot make enough new blood cells for your body to work normally)
* vertigo
* n/v
PO induces metaoblism by stimulating p450 enzymes in liver
DO NOT ADMINISTER TO PTS taking monoamine oxidase inhibitors
valprioc acid (depakote)
- enhance gaba neurotransmission postulated?
indication
* all sz types; particularly d/o of combined sz types
* manic ep in bipolar d/o
effects
* severe/fatal hepatotoxicity – small children especially
* less in adults
* thrombocytopenia (platelet count in your blood is too low)
* hyperammoemia (metabolic condition characterized by raised levels of ammonia, a nitrogen-containing compound. Ammonia is a potent neurotoxin)
* When you eat proteins, the body breaks them down into amino acids. Ammonia is produced from leftover amino acids, and it must be removed from the body. The liver produces several chemicals (enzymes) that change ammonia into a form called urea, which the body can remove in the urine.
PO/IV metabolized in liver, highly protein bound
interactions
* additive with other anticonvulsants
* levels decreased by aspirin and cimetidine (reduce gastric acid)
ethosuximide (zarontin)
indication
* absence sz
effects
1) n/v
2) decreased appetite
3) wt loss
PO – 40-100 mcg/ml
interaction
* inc’s phenytoin
* dec primidone
gabapentin (neurontin)
- related to GABA, likely reacts to distinct receptor
indication
* adjunctive tx of partial sz
indication
* somnolence (state of drowsiness or strong desire to fall asleep)
* ataxia
* dizziness
* CNS effects
PO
Gabapentin absorption dec by antacids
lamotrigine (lamictal)
- may stabilize neurons and affect glutamate (memory, cognition, and mood regulation) / aspartate (nutritional potential, regulation on reproduction and hormone biology, and neuron protection) release
- both at low levels can stimulate neurons
indication
* adult patients w/ partial seizures
* lennox-gastaut syndrome
* Lennox-Gastaut syndrome is a severe condition characterized by repeated seizures (epilepsy) that begin early in life. Affected individuals have multiple types of seizures, developmental delays, and particular patterns of brain activity measured by a test called an electroencephalogram (EEG). An EEG shows a slow spike-and-wave pattern during wakefulness and generalized paroxysmal fast activity during sleep.
effects
* dizziness
* headache
* nausea
* ataxia
* somnolence
* diplopia
* blurred vision
* life threatening rash in children (1:50) and adult (1:1000)
PO, induce own metabolism
interaction
* reduce dose if on valproate
topiratemate (topamax)
- r/t to GABA? or kainate/AMPA receptors (AMPA receptors were capable of driving a sustained train of action potentials while kainate receptors tended to activate action potential firing more transiently.)
indication
* partial onset sz
effect
* psychomotor slowing
* somnolence
* ataxia
* dizziness
* speech impairment
PO, reduce dose with kidney impairment
interaction
* reduce level of oral contraceptives
* Enhance CNS depressants
rufinamide (banzel)
- inhibit Na+ channel
indication
* lennox-gastaut syndrome sz (severe condition characterized by repeated seizures (epilepsy) that begin early in life. Affected individuals have multiple types of seizures, developmental delays, and particular patterns of brain activity measured by a test called an electroencephalogram (EEG). An EEG shows a slow spike-and-wave pattern during wakefulness and generalized paroxysmal fast activity during sleep.)
effect:
* CNS adverse effects
PO
drugs that reduce liver enzymes ==> inc this drug’s metabolism
zonisamide (zonegran)
- may block na+ channel
- or facilitate dopamine or serotonin
indication:
* partial onset seizure
effects
1) elevated body temp in some children
2) agitation
PO
drugs that reduce liver enzymes ==> inc this drug’s metabolism
levetirceptam (keppra)
levetiracetam (spritam)
- unknown mechanism
indication
* myoclonic ( brief, jerking spasms of a muscle or muscle group.), partial onset, primary generalized
effects
1) somonolence
2) dizziness
3) BH change
PO
- may cause toxicity with carbamazepine
