AED'S and Anti- Convulsants: Flashcards
Phenytoin:
-Used to treat Partial Seizures Voltage gated Na+ channel blocker -Undergoes CYP liver metabolism -Enzyme inducer -Uses zero order kinetics AE's: Gum Hypertrophy, cerebellar atrophy imbalance and teratogenicity
Carbamazepine:
-Used to treat Partial Seizures
Voltage gated Na+ channel blocker
-Undergoes CYP liver metabolism
-Enzyme inducer of itself/ other medications such as estrogen & oral contraceptives
AE’s: Rash, Hyponatriemia, Bone Marrow Suppression, Osteoporosis and Teratogenicity
Oxcarbazepine:
-Used to treat Partial Seizures
-Voltage gated Na+ channel blocker
-Undergoes P450 metabolism by the liver
-Less of an enzyme inducer than Carbamazepine
AE’s: Rash, High chance of hyponatriemia and a reduced chance of bone marrow suppression, osteoporosis and teratogenicity compared to Carbamazepine
Lamotrigine:
Voltage Gated Na+ channel blocker
-Used to treat Generalized/ Partial Seizures
-Metabolized by glucuronic acid (glucuronidation)
-If commanded with VPA, VPA induces its metabolism and increases Lamotrigine levels by a 2 fold (can lead to toxicity)
-Lamotrigine levels decrease during pregnancy (estrogen presence) and with the use of oral contraceptives as these induce Lamotrigine metabolism
AE’s: Rash, but safe to use during pregnancy (always add folate)
Lacosamide:
- Used to treat Partial Seizures
- Slow potentiation of inactivated Na+ channels
- Prolongation of cardiac contraction (PR interval)
- -Important to do a baseline ECG in patients with unknown cardiac disease or conduction effects
Valproic Acid (VPA):
-Used to treat Generalized/ Partial Seizures
-Voltage gated Na+ channel blocker/ GABAergic effects (increases GABA concentrations in the brain) @ high enough concentrations
-Main mechanism is through Ca2+ channel blocker
-Promotes increased K+ channel permeabilty
-Heavy protein binding capacities (can displace other drugs & lead to toxicity)
-Blocks liver metabolism and is decreased by P450 enzyme inducers such as Phenytoin
AE’s: Tremor, platelet dysfunction, hepatotoxicity, pancreatitis, hair loss, weight gain, polycystic ovaries and HIGH teratogenic effects.
-NEVER use with a pregnant women and try to avoid in young fertile women.
Phenobarbital:
- GABAergic effect (glutamate antagonist)
- Increases duration of Cl- Channel opening
- Used to treat neonatal seizures/ partial seizures
Benzodiazepines:
- Diazepam, Lorapezam, Midazolam, Clobazam and Clonazepam
- Increase frequency of Cl- channel opening
- Benzodiazepine withdrawal can induce seizures
Tiagabine:
- Blockade of GBA transporters (GAT-1) in neurons and glial cells
- Can cause depression and psychosis
- Used to treat Partial Seizures
Vigabatrin:
- Inhibits GABA transaminase (GABA-T), which inhibits the breakdown of GABA
- Can cause loss of vision/ retinitis
- Used to treat Partial Seizures
Lorazepam and Midazolam
- Intravenous drugs
- Used in emergency situations only to treat seizures
Diastat:
Rectal Diazepam:
-Can be given to children to treat seizures
Clobazam and Clonazepam:
-Used for the long term treatment of seizures
Primidone:
Barbiturates
- Occasionally used to treat tremors- not used to treat seizures anymore
- Used to be used to treat partial seizures
What is the worst adverse effect of a possible Benzodiazepine or Barbiturate’s overdose?
–>Respiratory failure/ arrest and death!
Ethosuximide:
- T- type Ca2+ channel blocker in the Thalamic neuronal relay centre
- Specific for ABSENCE SEIZURES
Zonisamide:
Voltage gated Na+ channel blocker
- Not approved for children
- Used to treat Generalized/ Partial Seizures
Gabapentin / Pregabalin:
- Pre-synaptic voltage gated Ca2+ channel blockers
- Structure similar to that of GABA
- Binds to alpha2gamma subunit of the presynaptic voltage gated Ca2+ channel, leading to a decrease in glutamate excitatory release
- Used to treat Partial Seizures
Felbamate:
NMDA Blocker
-Used to treat Generalized/ Partial Seizures
Topiramate:
AMPA Blocker
-Used to treat Generalized/ Partial Seizures
Perampanel:
AMPA Blocker
Ezogabine:
Increased K+ channel permeability
-Used to treat Partial seizures
Levetiracetam:
Exocytotic apparatus inhibitor
- ->Binding of the drug to SV2A subunit of the exocytotic apparatus inhibits the release of neurotransmitter from the synaptic vesicles
- Used to treat Generalized/ Partial Seizures
What is VPA’s effect on Lamotrigine?
Increases levels of Lamotrigine by a 2 fold.
What is VPA’s effect on Phenytoin?
Increases these levels (induces it- can cause toxicity)
What is Carbamazepine’s effect on itself?
- Induces it’s own metabolism
* Lower’s levels of the drug
Drugs with common DDI’s?
Carbamazepine, Phenobarbital and Phenytoin
True or False: It’s safe to add more than 1 AED to a drug regimen within the same mechanism.
FALSE!
-If you need to add another AED, it must be of another mechanism.
