Epilepsy Flashcards
What are the three main mechanisms of action for antiepileptic drugs?
- Blocking voltage-gated channels (Na+ or Ca2+).
- Enhancing inhibitory GABA-ergic impulses.
- Interfering with excitatory glutamate transmission.
Which voltage-gated channels do some antiepileptic drugs block?
Voltage-gated Na+ or Ca2+ channels.
How do some antiepileptic drugs affect GABA-ergic impulses?
They enhance inhibitory γ-aminobutyric acid (GABA)-ergic impulses.
How do some antiepileptic drugs interact with glutamate transmission?
By interfering with excitatory glutamate transmission.
What is the mechanism of action of benzodiazepines as antiepileptic drugs?
Benzodiazepines bind to GABA inhibitory receptors, reducing neuronal firing rate.
Which two benzodiazepines are used for treating epilepsy?
- Diazepam.
- Lorazepam.
What types of seizures do benzodiazepines treat?
- Myoclonic seizures.
- Partial seizures.
- Generalized tonic-clonic seizures.
How is diazepam is used for emergency seizure treatment?
Rectal administration to avoid prolonged generalized tonic-clonic seizures.
Which benzodiazepine is administered rectally in seizure emergencies for generalized tonic-clonic?
Diazepam.
What is the first-line treatment for status epilepticus (FDA guideline)?
Benzodiazepines.
What is the mechanism of action of carbamazepine?
Blocks sodium channels, inhibiting repetitive action potentials in epileptic focus and preventing their spread.
What types of seizures is carbamazepine effective for?
Partial seizures and secondarily generalized tonic-clonic seizures.
What non-epileptic conditions can carbamazepine treat?
Trigeminal neuralgia and bipolar disorder.
What is a key metabolic characteristic of carbamazepine?
It induces its own drug metabolism.
What is a dangerous side effect of the epoxide metabolite of carbamazepine?
Blood dyscrasias.
What enzyme families does carbamazepine induce?
CYP450s and UGT enzymes.
Why should carbamazepine not be prescribed for absence seizures?
It may cause an increase in seizures due to GABA receptor activation in the ventrobasal complex.
What are two ophthalmic side effects of carbamazepine?
Diplopia (double vision) and blurred vision.
What electrolyte imbalance can carbamazepine cause, and why?
Hyponatremia (due to ADH secretion).
What is the active form of oxcarbazepine?
Monohydroxy (MHD) metabolite.
How does oxcarbazepine exert its anticonvulsant effect?
Blocks sodium channels, preventing spread of abnormal discharge.
What type of seizures is oxcarbazepine used to treat?
Partial onset seizures.
How does oxcarbazepine compare to carbamazepine in enzyme induction?
Less potent inducer of CYP3A4 and UGT.
What is an advantage of oxcarbazepine’s lower enzyme induction?
Low drug-drug interactions.
List four common side effects of oxcarbazepine.
Nausea, vomiting, headache, and visual disturbances.
What is the primary mechanism of action of phenytoin and fosphenytoin?
Blocks voltage-gated sodium channels by selectively binding to the channel in the inactive state and slowing its rate of recovery.
What secondary effects does phenytoin have at very high concentrations?
a) Blocks voltage-dependent calcium channels.
b) Interferes with the release of monoaminergic neurotransmitters.
What types of seizures is phenytoin effective in treating?
- Partial seizures.
- Generalized tonic-clonic seizures.
- Status epilepticus.
Besides epilepsy, what other condition is phenytoin used to treat?
Trigeminal neuralgia.
Why should phenytoin not be used for absence seizures?
It has the potential to exacerbate absence epilepsy.
What enzyme system does phenytoin induce?
Drug-metabolized enzyme system.
How does phenytoin’s enzyme metabolism change at low serum concentrations?
It becomes saturable.
What can result from small increases in phenytoin’s daily dose?
Large increases in plasma concentration, potentially leading to drug-induced toxicity.
What CNS-related side effect can phenytoin cause?
Depression of the CNS, causing nystagmus (rapid involuntary eye movements) and ataxia.
What dental side effect is associated with phenytoin use?
Gingival hyperplasia.
What long-term neurological side effect may phenytoin cause?
Development of peripheral neuropathies.
What bone-related side effect is associated with long-term phenytoin use?
Osteoporosis.
What type of anemia is phenytoin associated with?
Risk of megaloblastic anemia.
What is fosphenytoin in relation to phenytoin?
Fosphenytoin is a prodrug that is rapidly converted to phenytoin in the blood.
Which antiepileptic drug is an analog of GABA?
Gabapentin.
What is the mechanism of action of gabapentin?
Unknown. It doesn’t bind to & activate GABA receptors.