Exam 6 Flashcards
Partial Seizure
Begins focally, in a single site in the cortex.
Simple = consciousness preserved
Complex = Loss of consciousness
Generalized Seizure
Involves both cortices from the start
Absence, tonic-clonic, and myoclonic seizures are examples of generalized seizures
Secondary Generalized Seizure
Starts as a partial seizure and then spreads to become generalized
4 Anticonvulsants that Inhibit Na+ Channels in neuron
Carbamazepine Oxycarbazepine Phenytoin Valproic Acid These act by prolonging the "Inactive State" of the Voltage Gated Na Channels COP-V
What types of channels are involved in absence seizures?
T-Type Calcium Channels
2 Anticonvulsants that inhibit T-Type Calcium Channels
Ethosuximide
Valproic Acid
Name 1 GABA reuptake inhibiting anticonvulsant
Tiagabine
Name 1 inhibitor of GABA degradation in the synapse
Vigabatrin
Name three drugs and their classes that have an inhibitory effect on GABA(A) receptors
Phenobarbital (Barbiturate)
Primidone (Barbiturate)
Diazepam (Benzo)
Only 2 drugs effective for monotherapy in treatment of absence seizures
Ethosuximide
Valproic Acid
What were the original anticonvulsants (prior to 1912)? Side effects?
Bromides
Profound sedation and skin lesions
Phenobarbital
Monotherapy for tonic-clonic and partial seizures
Potentiates synaptic inhibition via GABA(A) receptors (agonist of GABA(A) I guess)
Significantly protein bound and metabolized by liver CYP enzymes (drug interactions based on these features)
Induction of CYP enzymes can lead to rapid degradation of other drugs like oral contraceptives ):
Teratogenic
Can cause cutaneous allergic reactions
Primidone
Like Phenobarbital, Monotherapy for tonic-clonic and partial seizures (It’s not as effective though)
Also Potentiates synaptic inhibition via GABA(A) receptors (GABA(A) agonist I guess)
Is metabolized to phenobarbital. The rate at which this happens if variable between patients.
Similar side effects to phenobarbital, but can also cause nausea, dizziness, nystagmus, and ataxia.
Phenytoin
Monotherapy for tonic-clonic and partial seizures (IV fosphenytoin for status epilepticus)
Prolongs Voltage gated Na channels’ rate of recovery from inactive state
Highly protein bound (albumin)
** Plasma concentration increases disproportionately as dosage increases (half-life increases)
Metabolized by CYP enzymes in the liver (drug interactions with Warfarin and oral contraceptives)
Side effect = Gingival hyperplasia in 20%
Stevens-Johnson Syndrome
Drug reaction that causes rash with more than 10% surface area, 5% mortality
Starts with flu-like symptoms, progresses…
Toxic Epidermal Necrolysis is worse (>30% SA, 20-40% mortality)
Carbamazepine
Monotherapy for tonic-clonic and partial seizures
Prolongs Voltage gated Na channels’ rate of recovery from inactive state
Metabolized to 10,11 epoxide, which is just as effective
Induces its own metabolism, making achieving constant plasma concentration difficult
Other anticonvulsants also induce its metabolism
Many side effects.
Induces CYP enzymes = drug interactions (oral contraceptives)
Oxycarbazepine
Monotherapy, adjunctive treatment for partial seizures, even in patients 4-16 years old
Prolongs Voltage gated Na channels’ rate of recovery from inactive state
It’s a prodrug, converted to active metabolite by the liver
Conjugated to glucuronide and excreted
Does not auto induce metabolism
Similar side effects to carbamazepine
Induces CYP, but not as much as carbamazepine
Ethosuxamide
Monotherapy for absence seizures
Inhibits T-Type Ca channels
Not protein bound, few drug interactions
Side effects: nausea, vomiting, anorexia. CNS depression, lethargy. SJS, aplastic anemia.
Valproic Acid
Mono therapy of pretty much all types of seizures
Inhibits T-Type Ca channels, Prolongs Voltage gated Na channels’ rate of recovery from inactive state, and increases GABA synthesis
Highly protein bound, can inhibit certain CYP enzymes and increase hepatic blood enzymes (whatever that means)
Gabapentin
GABA molecule bound to a lipophilic hexane ring
Doesnt act on GABA receptors, but does decrease neuronal activity
Adjunctive treatment for partial seizures, neuropathic pain, and fibromyalgia
Mechanism isn’t really known, it binds to L-type Ca channels, but Ca flow doesnt change.
Not metabolized, excreted in its original form in urine (renal function important)
Side effects: fatigue/ataxia
Lennox-Gustaut Syndrome
Childhood-onset epilepsy Severe cog dysfunction multiple seizure types resistant to drugs Can be deadly Ketogenic diet?
Lamotrigine
Broad spectrum anti epileptic drug (partial and generalized seizures)
Prolongs Voltage gated Na channels’ rate of recovery from inactive state.
Also inhibits Ca channels to some extent
Other AEDs reduce its half life
SEs- dizziness, ataxia, blurred vision, nausea, rash, SJS
Topiramate
Broad spectrum anti epileptic drug (partial and generalized seizures and LGS)
Inhibits Na channels and AMPA-kainate receptors enhance GABA receptors
Not highly protein bound, excreted unmetabolized in urine
SEs- Anorexia, weight loss, fatigue, somnolence
Reduces plasma levels of oral contraceptives
Levetiracetam
Adjunctive treatment for generalized, partial seizures in adults, myoclonic seizures in children.
IV prep for status epilepticus
May prevent synaptic glutamate release???
high safety margin, rapid dose titration, 3-D printing?
Status Epilepticus
Series of seizures where full recovery doesnt happen before onset of next seizure (20% mortality)
Treat with IV Lorazepam or Diazepam (lorazepam is better)
Once seizures are controlled, give IV fosphenytoin (alternatives are levetiracetam, phenobarbital, valproic acid)
What is one cause that long term AED use can cause?
Osteoporosis
Unknown mechanism (altered vit D metabolism?)
Monitor bone density in the elderly.
AEDs and Pregnancy
They screw with oral contraceptives, making pregnancy 3x more likely.
Also cause neural tube defects, fatal hydantoin syndrome (especially phenytoin)
Mono therapy is preferable to combo
Give vit K and folate to help prevent birth defects
Carbonic anhydrase inhibitor
Acetazolamide
Complication associated with acetazolamide
Serious skin reactions because it is an sulfonamide
Structure of acetazolamide
Sulfonamide
Where do carbonic anhydrase inhibitors act?
Proximal convoluted tubule
Acetazolamide
Diuretic
Carbonic anhydrase inhibitor, acts in the proximal convoluted tubule
CA normally converts bicarb to water and CO2, allowing the reabsorption of Sodium bicarb
They aren’t super effective because there are so many other places downstream where sodium can be absorbed.
Loss of bicarb can lead to metabolic acidosis.
Treats glaucoma by decreasing intraoccular pressure by inhibiting production of aqueous humor
Treats respiratory alkalosis (acute mountain sickness)
Treats cerebral edema (decreases CSF production)
Can treat epilepsy
Can be used to alkalinize the urine, enhancing excretion of weak acids (Uric acid and aspirin). This can cause kidney stones.
Can cause hypokalemia due to indirect K+ excretion
Sulfonamide allergic reactions
Mannitol
Osmotic diuretic
It gets filtered through the the glomerulus into the tubule lumen
Also decreases reabsorption of other solutes like sodium
Can be used to induce urine flow in acute renal failure
Can be used to decrease cerebral edema
Can also lower intraoccular pressure
Can pull water our of cells and into extra cellular space, which is dangerous in patients with CHF
2 loop diuretics
Furosemide (a sulfonamide)
Ethacrynic acid
How do loop diuretics get into the lumen?
Secreted by the organic acid secretory system.
Can increase Uric acid, bad for gout.
Loop diuretic mechanism
Inhibit the sodium potassium chloride transporter in the thick ascending limb of the loop of henle, inhibiting the reabsorption of all three ions.
Leads to excretion of other ions like magnesium and calcium
Drug of choice for CHF pulmonary edema
Treats edema caused by liver and kidney problems
Treats hypertension if thiazides fail
Can treat hypercalcemia
Leads to profound fluid/electrolyte loss
Can cause metabolic alkalosis by increasing H secretion in the collecting ducts
Can cause hypokalemia due to increased K secretion the collecting ducts
Can increase glucose and lipids
Can exacerbate gout by decreasing secretion of Uric acid and increased Uric acid reabsorption due to hypovolemia
Can also cause ototoxicity
Allergic reactions due to its sulfonamide structure
Uses of loop diuretics
Pulmonary Edema due to CHF
Edema due to cirrhosis, nephrotic syndrome
HTN if Thiazides fail
Hypercalcemia
Adverse Effects of Loop Diuretics
Profound electrolyte/fluid loss can lead to hyponatremia, hypovolemia
Metabolic alkalosis due to increased secretion oh H+ in the collecting duct
Hypokalemia
Increased serum glucose and lipids
Can exacerbate gout because they are secreted into the lumen via the same organic acid secretory mechanism as uric acid and also because hypovolemia can cause increased uric acid reabsorption in the proximal tubule
Ototoxicity
Sulfonamide-like allergic reactions
Name 4 thiazides
Hydrochlorothiazide Chlorothiazide Chlorthalidone Indapamide CHIC
What chemical group do thiazides have?
Sulfonamide
How to Thiazides get into the lumen of the tubule?
Filtered through the glomerulus but also secreted by the organic acid secretory mechanism in the proximal tubule.
Which Thiazide is the most/least potent?
Chlorothiazide is the least potent
Indapamide is the most potent
Which Thiazide has the shortest/longest half-life?
Chlorothiazide has the shortest half-life
Chlorthalidone has the longest half-life
Thiazide mechanism
Inhibition of the Na+Cl- symporter in the distal convoluted tubule
Uses of Thiazides
Tx of mild-moderate pulmonary edema due to CHF
Hypertension
Kidney stones- Thiazides indirectly increase the reabsorption of Ca in the distal convoluted tubule
Nephrogenic DI
Can have a paradoxical anti-diuretic effect
Adverse effects of Thiazides
Hypokalemia- increased K+ secretion in collecting ducts
Metabolic alkalosis- increased H+ secretion in the collecting ducts
Same negative effects with gout as loop diuretics
Hyperglycemia- maybe due to decreased insulin release
Hyperlipidemia
Hypersensitivities to Sulfa (SJS)
So pretty similar to adverse effects of loop diuretics…
Which Thiazide isn’t as bad when it comes to causing hyperlipidemia?
Indapamide
How do K+ wasting diuretics waste K+?
They increase both Na+ and Cl- delivery to the collecting duct system. The collecting duct system is faster at reuptaking Na+ than Cl-, which leaves the lumen of the collecting ducts relatively more negative.
This promotes more secretion of K+
Name 2 K+ sparing diuretics
Triamterene
Amiloride
How to K+ sparing diuretics get into the lumen of the tubules?
Via the organic BASE secretory system in the proximal tubules.
Mechanism of Amiloride and Triamterene
Inhibit apical Na+ channels in the collecting ducts
This leaves more Na+ in the ducts and promotes diuresis
It also makes the lumen more positively charged, inhibiting K+ secretion, sparing K+.
Uses of Amiloride and Triamterene
Often used in combo with K+ wasting diuretics to prevent hypokalemia
Can decrease thickness of respiratory secretions in CF
Also treats Liddel’s Syndrome (pseudohyperaldosteronism)
Adverse effects of Amiloride and Triamterene
Hyperkalemia
Contraindicated with aldosterone antagonists (spironolactone)
Used cautiously with RAAS inhibitors
Nausea/vomiting is common
Triamterene is poorly soluble in urine and can cause kidney stones
Name 3 aldosterone receptor antagonists
Spironolactone
Eplerenone
Drospirenone