Drugs for Seizures Flashcards
Phenytoin: mechanism, use, contraindications, common names?
Slows the rate of Na channel recovery post-inactivation, preventing repetitive firing of neurons in rapidly opening/closing channels and ∴ stopping the rapid spread of seizures to other neurons.
Treats partial and generalised seizures.
Has complex pharmacokinetics and binds to plasma proteins, causing weird drug interactions
AKA Dilantin
Carbamezapine: mechanism, use, contraindications, common names?
Similar mechanism to phenytoin (slowing Na channel recovery rate) although not structurally related.
Treatment of partial and generalised seizures.
Some drug interactions, induces metabolic enzymes and increases metabolism of other drugs
AKA Tegretol
Lamotrigine: mechanism, use, common names?
Slows rate of Na channel recovery post-inactivation, possibly also inhibits excitatory transmitters.
Partial and generalised seizures + also absence seizures
AKA Lamictal
What are T-type Ca channels used for in the brain?
Important for sending information from the thalamus to the cortex as it’s received (series of spikes) via a cortical excitatory neuron. Burst firing can cause excitation, which becomes self-sustaining, and an absence seizure.
Ethosuximide: mechanism, use, contraindications, common names?
Specific to T-type Ca channels, which are depolarised and inactive during the awake state. Ethosuximide lowers the currents in a voltage-dependent manner but doesn’t affect Na channels or GABA neurons.
Used for absence seizures.
GIT effects and transient fatigue.
AKA Zarontin
Valproate: mechanism, use, contraindications, common names?
Slows Na channel recovery from inactivation, limits activity of low threshold T-type Ca channels and increases the activity of glutamic acid decarboxylase (increases GABA synthesis) + inhibits activity of enzymes that degrade GABA.
Use for primary generalised seizures, simple/complex partial seizures and bipolar disorder.
AKA Valproic acid, Epilim
Clonezapam: mechanism, use, contraindications, common names?
A benzodiazepine. Potentiates GABAa channels in the reticular thalamic nucleus and decreases the activation of inhibitory reticular neurons and stopping hyperpolarisation of relay neurons. Also inhibits T-type Ca channels.
Used for absent seizures, adjunct for epilepsy refractive to other treatment and acute seizure treatment.
Barbituates: mechanism, use, contraindications, common names?
Increase duration of GABA-A Cl- channel opening.
Used for simple and complex partial seizures, generalised tonic-clonic seizures, neonatal and febrile seizures.
Cause decreased respiratory drive.
Common names: phenobarbitone, primidone.
Benzodiazepines: mechanism, use, contraindications, common names?
Act on GABAa Cl- ion channel to increase frequency of opening (GABA must be present), decreasing the reach of its effect and hence peripheral side effects also.
Adjunct for epilepsy refractive to other drugs, acute seizure treatment including status epilepticus.
Common names: Diazepam, clobazam, midazolam
Gabapentin: mechanism, use, contraindications, common names?
Thought to be a lipophilic GABA analogue for epilepsy as GABA can’t cross the BBB, doesn’t act on GABAa receptors - we now realise we don’t actually know the mechanism. Enhances GABA release, inhibits Na channels, inhibits N-type Ca channels, increases intracellular GABA levels and inhibits high voltage activated Ca channels.
Use for partial seizures (not for absent as it does N-type not T-type Ca channels)
Negligible drug interactions.
Carbonic anhydrase inhibitors: mechanism, use, contraindications, common names?
Inhibit carbonic anhydrase (bicarb synthesis), accumulating CO2 in the brain and acidifying cells which may reduce the spread of seizure activity. Also slow down excessive discharge in neurons.
Used as anticonvulsants.
Common names: acetylxolamide, sulthiame.
Vigamatrin mechanism?
Inhibits GABA transaminase - prevents GABA degradation.
Tiagabine mechanism?
GABA reuptake inhibitor.
Topiramate mechanism?
Blocks voltage-dependent Na channels and enhances GABA effects through blocking reuptake, blocks AMPA glutamate channels (unique).
Lacosamide mechanism?
Stabilises neuronal membranes by enhancing inactivation of voltage-dependent Na channels, used for partial seizures with or without secondary generalisation.
