Neurology Flashcards
Define Seizures
Transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain
~ 10% of the population will experience a seizure
Benign febrile seizure occurs in 2 – 5% of children < 5 years of age
- Centralized Seizures
- Focal Seizures
Epilepsy
- Disorder of the brain characterized by an enduring predisposition to seizures
- Epilepsy requires the occurrence of at least one epileptic seizures
- ~ 1% of the general population will develop epilepsy
Focal seizures include…
specific aura, motor autonomic features
Pharmacotherapy of Seizure Control (3)
- Anti-Epileptic drugs (AEDs)
- Ketogenic
- Vitamin Supplementation
Carbamazepine (Tegretol)
MOA
Indications (2)
MOA
- Blocks sodium channels to decrease frequency and voltage of rapidly firing nerve cells
Indications
- Tonic-Clonic Seizures
- Focal Seizures
Carbamazepine (Tegretol) Adverse Effects (4)
- Ataxia
- Diplopia
- Hyponatremia
- Stevens-Johnson Syndrome
Carbamazepine (Tegretol)
Drug-drug interactions (3)
- CYP3A4 substrate and inducer (makes half-life variable depending on duration of treatment). At induction is complete within 3 – 5 weeks
- Strong inhibitor for CYP2C19, 2C9, 1A2
- Moderate inhibitor of 2B6
Benzodiazepines
MOA
PK (2)
ADE (4)
MOA
- Binds to GABAA receptor increasing the activity of GABA
PK:
- Similar efficacy
- Onset of action and half-life differ
Adverse Effects
- Respiratory Depression
- Hypotension
- Bradycardia
- Delirium
Benzodiazepines
Indications (4)
Available Agents (4)
Indications
- Delirium Tremens
- Absence Seizures
- Myoclonic Seizures
- Status Epilepticus
Available Agents
- Diazepam (Diastat®/Valium®)
- Lorazepam (Ativan®)
- Midazolam (Versed®)
- Clonazepam (Klonipin®)
Benzodiazepines
Clinical Pearls
Other uses (3)
Administration and dosage forms (4)
Other Uses
- Nausea and Vomiting
- Pre-procedure sedation
- Anxiety
Administration andƒ dosage forms
- Diazepam: IV/PO/PR (Diastat®)
- Lorazepam: IV/PO
- Midazolam: IV/PO
- Both lorazepam and midazolam can be administered intranasally
Ethosuximide, Zarontin
MOA
Indications
MOA
- Succinamide
- Blocks sodium and calcium channels
Indications
- Absence Seizures **ONLY INDICATION
Ethosuximide, Zarontin
ADE
Clinical Pearls
Adverse Effects
- Blood dyscrasias
Clinical Pearls
- Many drug interactions (CYP3A4)
- Can measure serum concentrations
Phenytoin (Dilantin)
Mechanism Of Action
Blocks sodium channels to decrease frequency and voltage of rapidly firing nerve cells
Phenytoin (Dilantin)
Absorption and therapeutic drug concentrations
Absorption: Variable depending on dosage form (increase with food)
Therapeutic drug concentration
- Total = 10 – 20 mcg/ml
- Unbound = 1 – 2 mcg/ml
Phenytoin (Dilantin)
Distribution
Highly protein bound
Adjusted C = C/0.2 x serum albumin + 0.1
Phenytoin (Dilantin)
Metabolism
Half-life
Metabolism
- CTP 2C9 and 2C19
Half-Life
- Depends on formulation
Phenytoin (Dilantin)
Indications (3)
Effects (4)
Indications
- Neonatal seizures
- SE
- Prevention of seizures following trauma or surgery
Effects
- Lethary
- Bradycardia
- Hirsutism
- Gingival hyperplasia
Phenytoin (Dilantin)
Clinical Pearls (2) Drug-drug interactions (2)
Clinical Pearls
- Pay attention to dosage forms
- Due to half-life it will take about 1 week to reach steady state with dose changes
Drug-drug interactions
- Inducer of CYP3A4
- CYP2C9 and CYP 2C19 substrate
Fosphenytoin (Cerebyx)
Place in Therapy Clinical Pearls (2)
Place in therapy
- Short-term parenteral administration for same indications as phenytoin
Clinical Pearls
- Should always be dosed in milligrams of Phenytoin Equivalents (PE)
- Optimal IV choice in pediatrics due to the risk of extravasation with phenytoin
Oxacarbazepime (Trileptal)
MOA
PK (2)
Mechanism of Action
- Acts on voltage-gated Na+ channels inhibiting neuronal synaptic impulses
PK:
- Bioavailability is not consistent with immediate release and extended release (caution when switching)
- Does not auto-induce metabolism
Oxacarbazepime (Trileptal) Side effects (5)
- Hyponatremia
- Pancytopenia
- Hypothyroidism has been reported (as well as altering TFTs)
- Hypersensitivity skin reaction (SJS)
- DRESS
Valproic Acid, Divalproex Sodium (Depakote, Depakene)
MOA
PK (3)
Mechanism of Action:
- Exact mechanism is undefined but likely acts as a GABA aminotransferase inhibitor; increases GABA concentrations
PK:
Absorption – Variable depending on dosage form
Distribution – Highly protein bound (80 – 90%)
Metabolism – Extensive hepatic metabolism via glucuronidation
Valproic Acid, Divalproex Sodium (Depakote, Depakene)
Therapeutic monitoring
Therapeutic: 50 – 100 mcg/ml
Toxicity: > 100 mcg/ml can see toxic effects (but sometimes have to get close to 100 to see effectiveness)
Valproic Acid, Divalproex Sodium (Depakote, Depakene) Side Effects (6)
- Pancreatitis
- Alopecia
- Rash (including SJS)
- GI abdominal pain, N/D/V
- Thrombocytopenia
- Hepatic toxicity (especially in neonates)
Valproic Acid, Divalproex Sodium (Depakote, Depakene) Dosage Forms (4)
Capsules and Tablets (IR and ER)
Sprinkles in capsules
IV
Oral solution
Gabapentin (Neurontin)
MOA (3)
Dosing
MOA
- Complete MOA unknown.
- Structurally related to GABA but does not bind to GABA sites on the receptor.
- Potentially do to calcium channel blockade
Dosing
- Start low and titrate up due to risk of side-effects
Gabapentin (Neurontin)
Indications (2)
- Focal Seizures
- Neuropathy – very beneficial for adjunctive therapy
*DO NOT GIVE FOR ABSENCE AND MYOCLONIC SEZIURES
Gabapentin (Neurontin)
ADE (4)
Clinical Pearls
Adverse Effects o Somnolence o Weight gain o Neutropenia o Nystagmus
Clinical Pearls
o May exacerbate absence and myoclonic seizures
*DO NOT GIVE FOR ABSENCE AND MYOCLONIC SEZIURES
Lamotrigine (Lamictal)
MOA (2)
Indications (3)
MOA
- Blocks sodium and calcium channels
- Inhibits excitatory neurotransmitter release
i. e. glutamate
Indications
- Focal Seizures
- Generalized Seizures
- Potential Absence Seizures
Lamotrigine (Lamictal)
ADE (3)
Clinical pearls (4)
Adverse Effects
- Skin Rash
- Stevens-Johnson Syndrome
- Toxic Epidermal Necrolysis
Clinical Pearls
- Significant drug interactions (valproate)
- Valproate increases serum concentration of lamotrigine
- Rashes are usually delayed
- Because of the skin rash an uptitration schedule is required
Levetiracetam (Keppra)
MOA
Indications
MOA
- Blocks calcium channels
- Potential reduction of GABA and glutamate
Indications
- Adjunct therapy
- Neonatal seizures
- Status epilepticus
- Increasingly becoming first-line and monotherapy
Levetiracetam (Keppra)
Side effects (3)
ADE (3)
Side Effects
o Somnolence
o Asthenia
o Nervousness
Adverse Effects
o Somnolence
o Asthenia
o Nervousness
Topiramate (Topamax)
MOA (3)
Indications (2)
MOA
- Sodium and Calcium channel blockade
- Carbonic anhydrase inhibition
- GABA potentiation and glutamate receptor antagonism
Indications
o Focal Seizures
o Generalized Seizures
Topiramate (Topamax)
ADE (3)
Clinical Pearls
Adverse Effects
o Concentration difficulties
o Anorexia
o Hyperthermia
Clinical Pearls
o Caution in patients with existing baseline behavioral or learning disabilities
Zonisamide (Zonegran)
MOA (3)
Indications
ADE (3)
MOA
- Sodium and calcium channel blockade
- Carbonic anhydrase inhibition
- GABA potentiation and glutamate receptor antagonism
Indications
- Adjunct therapy for focal seizures
Adverse Effects
- Cognitive impairment
- Oligohydrosis (deficient sweat production)
- Fatigue
Banzel (Rufinamide)
MOA
FDA approved for lennox-gaustaut syndrome (LGS) in patients > 1 year of age
Mechanism of Action
- Proposed: prolongs the inactive state of Na channels decreasing the Nadependent action potentials
Banzel (Rufinamide) Side effects (5) Product availability (2)
Side Effects
- Dizziness
- Headache
- Fatigue
- Nausea
- Severe: Steven Johnson syndrome and DRESS
Product availability
- Only as brand
- Tablets and Suspension
CX in patients with familial shortened QT
Sabril (Vigabatrin) FDA Approved (2)
Major side effect
FDA approved indications
- Refractory complex partial seizures (CPS) in children > 10 years
- Infantile spasms
Major side effect: vision loss
- Requires REMS enrollment
- Requires regular eye exams
Sabril (Vigabatrin)
MOA
Available doasge forms (2)
Mechanism of Action
- Irreversibly inhibits GABA transaminase (GABA-T) increasing GABA within the synapse and neuron
Available dosage forms
- 500 mg tablet or powder for administration
- Powder for suspension administration: Dissolve in 10 ml water (final concentration = 50 mg/ml); then draw up the required dose and discard the remainder (1 packet = 1 dose even if you do not use the whole packet)
Warnings and Discontinuation
Many of these agents have warnings on suicidal thoughts or increase in psychosis, etc.
Discontinuing anti-epileptic medications
o Avoid cold turkey
o Tapering off is recommended
Changing dosage forms
Ketogenic Diet
Dietary medical therapy used to treat intractable epilepsy
Fat provides majority of calories
o Protein: minimum RDA
o Carbohydrates: severely restricted
Today in conjunction with AEDs
o Watch CHO content
o Avoid liquids
o Content of carbohydrates can vary from generic to generic to brand
Vitamin Responsive Seizures
Pyridoxyl-5-phosphate (B6)
Folic Acid