| What are classifications of seizures? | Focal (only a portion of the brain, one lobe of one hemisphere, includes focal simple, focal complex and 2ary generalized)
Generalized (begins locally and progresses to include both hemispheres, 1ary generalized , could be convulsive or non-convulsive, with immediate loss of conscioussness |
| What are types of focal seizures? | Focal Simple (confined to a single locus in brain, no loss of conscious, abnormal activity of a single limb/muscle group, lasts 20-60 s)
Focal Complex (larger region of brain, conscious altered, lasts 30s - 2mins)
2ary generalized (both hemispheres + thalamus + brain stem, lasts 1-2 mins) |
| What are types of generalized seizures? | Tonic-Clonic (loss of conscious followed by tonicity (chronic contraction) and clonicity (rapid violent contraction and relaxation [grand mal]), in teens and young adults 11-23 yrs)
Absence (breif loss of conscious, impaired awareness, spaced out <30 s [petite mal], 3-5 yrs till puberty)
Myoclonic (no loss of awareness, occurs after wakening, brief limb jerks, at any age, puberty till early adulthood)
Status Epilepticus (2 or more seizures w/out recovery of full conscioussness more than 5 min, emergency tx by fast acting (benzodiazepines) and short acting (by phenytoin)) |
| What are drugs that are enhanced Na+ channel inactivators? | Phenytoin, Zonisamide, Carbamazepine, Lamotigrine, |
| What are actions and uses of phenytoin? | At therapeutic dose (block voltage gated Na+ channels)
At high dose (block voltage gated Ca2+ channels)
Use (Partial and tonic-clonic seizures, not for absence seizure, 1ary use for status epilepticus) |
| What are adverse effects of phenytoin? | Acute toxicity (cerebellum atrophy [ataxia, nystagmus, diplopia])
Chronic toxicity (gingival hyperplasia, osteoporosis, peripheral neuropathy, allergic rxns [Steven-Johnson syndrome], Hirutism, teratogenic effect) |
| How are drug-drug interactions of phenytoin? | Carbamazepine (enhances metabolism of phenytoin)
Valproate, Phenylbutazone, sulfonamide (displaces phenytoin from binding)
OCP (unplanned pregnancy)
Vit D and Vit K (phenytoin accelerates metabolism leads to osteoporosis and hyperthrombinemia) |
| How is pharmacokinetics of phenytoin? | Oral absorption, Fosphenytoin prodrug IV, 90% bound to plasma proteins, hepatic metabolism by CYP2C19, inducer of drug metabolism. |
| Give PHENYTOIN mneumonic. | . |
| What is zonisamide? | Sulfonamide derivative, blocks both Na+ and Ca++ channels
Use: refractory focal seizure
Effect: renal calculi, oligohydrosis [sweat deficiency] |
| What is carbamazepine? | Use: partial and tonic-clonic seizure, not absence seizure, trigeminal neuralgia, bipolar disorder/mood stabilizer
Oral, 70% bound to plasma proteins, oxcarbamazepine (prodrug)
Effects: hypersensitivity [steven-johnson], water retention and hyponatremia, blood dyscrasia [aplastic anemia], teratogenic effects. |
| What is lamotigrine? | Blocks Na+ and Ca2+ channels, uses: partial and generalized, absence and myoclonic, bipolar disorder.
Completely absorbed
Effects: blurred vision/dipolplia, steven-johnson.
Drug-Drug interaction: Valoproate: increase half life
half life decreases with phenytoin, carbamazepine and phenobarbitols. |
| What are drugs of enhanced inhibitory neurotransmission? | Barbiturates, Tiagabine, Levetiracetam, Gabapentin, Topiramate |
| What are barbiturates? | Only used for chronic therapy/multiple refractory periods resist many drugs.
Enhances inhibitory effects of GABA, at high doses blocks Na+ and Ca2+ channels
Pimidone is a prodrug
Uses: status epilepticus, focal seizures, generalized tonic-clonic.
Effects: sedation, osteoporosis. |
| What is tiagabine? | Inhibit GABA reuptake
Uses: adjunct for focal seizures, contraindicated for absence seizures like phenytoin and carbamazepine. |
| What is Levetiracetam? | Enhances GABA release and blocks glutamate
Uses: focal seizures, 2ary generalized tonic-clonic, myoclonic
effects: no interaction w/CYP or UTG. |
| What is Gabapentin? | block Ca2+ influx so blocks release of excitatory NT
Uses: focal seizures, neuropathic pain
Not bound to plasma proteins, no drug interactions, renal elimination unchanged so reduce dose in pt of renal diseases. |
| What is Topiramate? | Block voltage gated Na+, enhance action of GABA Rs, reduce high-voltage Ca2+ currents L type.
Uses: partial and generalized tonic-clonic seizures, migraine prophylaxis
Minimal plasma protein binding, rapidly absorbed, moderate metabolism.
Effects: OCPs less effective (like phenytoin)
acute myopia. |
| What are drugs that reduce excitatory neurotransmission? | Ethoxisumide, Divalproex (Valoproate) |
| What is ethoxisumide? | Blocks T-Ca2+ channels, used as 1ary treatment for absence seizure, complete absorption no protein binding, intreactions (valproic acid blocks metabolism) effects (gastric distress) |
| What is Valoproate? | Uses: all types of epilepsy, status epilepticus.
90% bound to plasma proteins
Effects: teratogenic, like phenytoin and carba
Drug- interactions: displaces phenytoin, blocks metabolism of phenytoin, carbamazepine, phenobarbitol, ethoxisumide, lamotigrine
Mechanism: reduces Ca2+ T current, prolongs inactivation Na+, increases GABA levels, blocks NMDA Rs |
| What are other drugs antiepileptics? | . |
| What are non enzyme inducers and AEDs in absence seizurees? | . |
