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Ahmed Neuro 2 Depression > Lecture 10: Antiepileptic Agents > Flashcards

Lecture 10: Antiepileptic Agents Flashcards

1
Q

List the 9 antiepileptic drugs which work as pre-synaptic voltage-gated Na+ channels blockers via enhanced fast inactivation.

A

1) Carbamazepine
2) Oxcarbazepine
3) Lamotrigine
4) Phenytoin
5) Rufinamide
6) Topiramate
7) Valproic acid
8) Zonisamide
9) Lacosamide

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2
Q

Which AED is unique in its ability to prolong fast inactivation of Nav ion channels and also enhance slow inactivation of Nav channels?

A

Lacosamide

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3
Q

Which 2 antiepileptic drugs are AMPA-receptor antagonists?

MOA?

A
  1. Topiramate
  2. Perampanel

MOA = bind AMPA receptor and block glutamate binding; channel doesn’t open –> AP does not propogate downstream

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4
Q

Which antiepileptic drug is an NMDA-receptor antagonist?

A

Felbamate

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5
Q

The pharmacological activity of AED Nav channel blockers is _______ and ________-dependent

A

State and Use-dependent

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6
Q

AED’s binding site is at the _________ side Nav channel ‘pore’

A

Interior

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7
Q

Which gate must be open for AED’s to access the pore of Nav channels?

Which states can this occur?

A
  • Activation gate
  • Open state and Fast-inactivated state
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8
Q

The probability of Nav blockade is proportional to what?

A

FREQUENCY of Nav channel opening and dose

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9
Q

Why do the AED’s that are Nav blockers act preferentially on the neurons involved in epileptic seizures?

A

The neurons involved will be firing at higher freqeuncy than normal, allowing more chances for these drugs to slip right in and bind

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10
Q

What is the water-soluble pro-drug of phenytoin which is given via IV and is an Nav channel blocker used as an antiepileptic?

A

Fosphenytoin

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11
Q

Which AED acts as a Nav channel blocker (fast inactivation), AMPA-receptor antagonist, and GABAA agonist?

A

Topiramate

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12
Q

What occurs when the post-synaptic GABAA receptor becomes occupied by GABA?

A
  • Cl- channel opens
  • Hyperpolarization occurs blunting AP propogation
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13
Q

What is the MOA of the AED, Tiagabine?

A
  • Blocks pre-synaptic reuptake of GABA by blocking the GABA transporter, GAT-1
  • Causes GABA to go post-synaptically, bind GABAA receptor leading to hyperpolarization and decreased AP propogation
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14
Q

What are the 3 MOA’s of Valproic acid used as a AED at the pre-synaptic GABA terminal?

A

1) Increase activity of glutamic acid decarboxylase, leading to increased GABA presynaptically
2) Inhibit GABA-T, which typically metabolizes GABA
3) Inhibit Succinic Semialdehyde Decarboxylase (SSD), which typically metabolized GABA

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15
Q

Which 2 AED’s inhibit the metabolism of GABA through the inhibition of GABA-T?

A
  1. Vigabatrin
  2. Valproic acid
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16
Q

Which drug in the barbiturate family gets metabolized to phenobarbital in the body?

A

Primidone

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17
Q

Where do Benzodiazepines bind the GABAA receptor and what effects does this have?

A
  • Bind to a distinct site –> Allosteric change potentiate GABA binding
  • Cl- channel opens with greater frequency
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18
Q

Where do Barbiturates bind the GABAA receptor and what is their effect?

A
  • Bind a distinct site
  • Increases the duration of Cl- channel opening
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19
Q

Of the GABAA receptor agonists used as AED’s which is more lethal at higher doses and why?

A
  • Barbituates are more lethal due to being GABA INdependent
  • Benzodiazepines are GABA-dependent
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20
Q

What are the 7 AED’s which act post-synaptically to potentiate GABAA-receptor Cl- currents?

A

1) Phenobarbital
2) Primidone
3) Clonazepam
4) Lorazepam
5) Diazepam
6) Clobazam
7) Topiramate

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21
Q

Which type of ion channel mediates the 3-Hz spike and wave activity in the thalamus which is the hallmark of absence (petit mal) seizures?

A

T-type Ca2+ channels

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22
Q

Which narrow spectrum drug is only used for absence seizures and only limits excitation (Ca2+ channels)?

A

Ethosuximide

23
Q

Which 3 AED’s are antagonists of T-type Ca2+ channels?

A
  1. Ethosuximide (narrow spectrum)
  2. Valproic acid (also GABA-T inhibitor and prolongs fast inactivation of Nav channels)
  3. Zonisamide (also prolongs fast inactivation of Nav channels)
24
Q

What is a complication of using Zonisamide as an AED in some patients?

A

Is a sulfonamide and people may have allergies

25
Q

Which 2 AED’s act as both antagonists of T-type Ca2+ channels and prolong fast inactivation of Nav channels?

A
  1. Valproic acid (also GABA-T inhibition)
  2. Zonisamide
26
Q

Which AED blocks synaptic vesicle 2A protein on the presynaptic terminal of glutamate neuron?

A

Levetiracetam

27
Q

Which 2 AED’s block the α2δ1 Ca2+ channel on the presynaptic terminal of the glutamate neuron?

A

1) Gabapentin
2) Pregabalin

28
Q

Which 5 AED’s are used as first-line treatment of both simple and complex partial onset seizures?

A
  1. Lamotrigine
  2. Oxcarbazepine
  3. Perampanel
  4. Primidone
  5. Lacosamide
29
Q

Which 3 AED’s are used for absence (petit mal) seizures?

A

1) Ethosuximide
2) Clonazepam
3) Valproic acid

30
Q

Which AED is used for myoclonic seizures?

A

Clonazepam

31
Q

Which 2 AED’s are used for Tonic/Clonic seizures?

A
  1. Primidone
  2. Phenytoin
32
Q

Which 4 AED’s are broad spectrum (i.e., partial onset and generalized onset, minus absence)?

A

1) Carbamazepine
2) Phenobarbital
3) Topiramate
4) Valproic acid

33
Q

Which 6 AED’s are used for Lennox-Gastaut seizures?

A
  1. Rufinamide
  2. Topiramate
  3. Clobazam
  4. Clonazepam
  5. Lamotrigine
  6. Felbamate
34
Q

Which 6 AED’s are used for Status Epilepticus seizures?

A
  1. Lorazepam
  2. Diazepam
  3. Phenobarbital
  4. Phenytoin
  5. Valproic acid
  6. Levetiracetam
35
Q

The abrupt withdrawl of any antiepileptic medication may precipitate?

May lead to what type of behavior?

A
  • Precipitate status epilepticus
  • Suicidal behavior and ideation
36
Q

Which AED follows zero-order (saturable) pharmacokinetics?

37
Q

Due to the pharmacokinetics of Phenytoin, what serum drug level must be monitored and maintained?

A

10-20 mcg/mL

38
Q

Phenytoin is a well-known inducer of?

A

CYP-450 enzymes

*Frequent drug-drug interactions

39
Q

What are 2 toxicities associated with the AED, Phenytoin?

A
  1. Gingival hyperplasia
  2. Hypocalcemia/Vit. D deficit/Osteoporosis
40
Q

Osteopenia/Osteoporosis is a side effect associated with chronic administration of which 4 AED’s?

What do these drugs induce?

A
  1. Carbamazepine
  2. Phenytoin
  3. Phenobarbital
  4. Valproic acid

*These drugs induce CYP450-dependent vitamin D catabolism

41
Q

What are some of the issues associated with the AED, Carbamazepine (i.e., serum drug level, inducer of, toxicities)?

A
  • Serum drug level monitoring (4-12 mcg/mL) = narrow window
  • Inducer of CYP-450 enzymes
  • Induces auto-induction (self-metabolism)
  • Hematological toxicities: leukopenia/neutropenia/thrombocytopenia
42
Q

Which AED induces its own metabolism?

Also occurs to a lesser extent with what other AED drug?

What may occur because of this?

A
  • Carbamazepine induces own metabolism
  • Also, to lesser extent (25%), with lamotrigine

*This may lead to a potential loss of efficacy and recurrence of seizures

43
Q

Before administering which AED is a CBC required as this drug has potential side effects including leukopenia, neutropenia, and thrombocytopenia?

A

Carbamazepine

44
Q

What analogue of carbamazepine was formulated which has fewer CNS/hematological SE’s and is a less-potent CYP450 inducer?

A

Oxcarbazepine

45
Q

What are some of the issues associated with the AED, Phenobarbital?

A
  • Need serum drug level monitoring (10-40 mcg/mL)
  • Well known inducer of CYP-450 enzymes (frequent drug-drug interactions)
  • Toxicities: hypocalcemia/Vit. D deficit/Osteoporosis
46
Q

Which AED is only prescribe-able via REMS program; why?

A
  • Vigabatrin
  • May cause progressive, permanent, bilateral, concentric vision loss
47
Q

Which 4 AED’s are associated with hepatic CYP450 induction?

A
  1. Carbamazepine
  2. Phenytoin
  3. Phenobarbital
  4. Valproate
48
Q

What are 3 major AED-drug interactions associated with the CYP450 inducers?

A
  1. Increased clearance of oral contraceptives –> 2-4 fold rise in OHC failure rate; risk for unplanned pregnancy
  2. Increase clearance of warfarin –> less anticoagulation; elevated risk for arterial/venous thrombosis
  3. Increase clearance of HIV meds –> elevated risk for HIV replication
49
Q

Which 2 AED’s inhibit conjugation of drugs by UGT causing accumulation of parent drug (esp. each other when used together)?

A

Valproic acid and Lamotrigine

50
Q

Which 3 AED’s induce conjugation of drugs by UGT causing a reduction of parent drug (i.e., when given with valproic acid will decrease levels of valproic acid)?

A

1) Phenytoin
2) Carbamazepine
3) Phenobarbital

51
Q

Which 6 AED’s require us to look at the renal function (i.e., serum creatinine/creatinine clearance); why?

A
  • Levetiracetam / Topiramate / Oxcarbazepine / Gabapentin / Pregabalin / Vigabatrin
  • 65-100% renal clearance; renal insufficiency requires dose adjustment
52
Q

What are some of the example causes of Status Epilepticus?

A
  • Abrupt withdrawl of AED’s, BZD’s, Opioid’s, Alcohol
  • Brain mass/trauma
  • Infection
  • Fever
53
Q

What is the initial therapy for convulsive status epilepticus (i.e., the first IV, alternative drug, and if no IV access)?

A

- In first IV:

  • Lorazepam

- Alternative

  • Diazepam

*Wait 1 minute for response then additional lorazepam PRN

  • If no IV access:
  • Midazolam via IM injection
54
Q

If treating convulsive status epilepticus adult and first IV treatment does not work, what are the AED’s used in the second IV treatment?

A
  • Fosphenytoin
  • Phenyotin
  • Valproic acid
  • Levetiracetam

Ahmed Neuro 2 Depression (16 decks)

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