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Pharm III Unit I > 2 Anticonvulsants > Flashcards

2 Anticonvulsants Flashcards

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1
Q

What are seizures exactly?

A

Abnormal discharges of electrical activity in cerebral neurons

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2
Q

Neurological disorder characterized by recurrent seizures

A

Epilepsy

1% of the world’s pop has it

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3
Q

Seizures typically originate in what part of the brain?

A

Cerebral cortex

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4
Q

What causes seizures?

A 
Can be...
Neurological disease
Head trauma
Infection
Tumors
Drugs
High fevers

About 50% have unknown origins

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5
Q

What are the different classifications of seizure?

A

Partial (originates in one are of the brain)
• Simple
• Complex
• Partial with 2˚ general

Generalized (involves whole brain)
• Absence
• Tonic-clonic
• Myoclonic
• Atonic
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6
Q

Name that seizure!

Focal
Brief (20-90 sec)
Grimacing, focal clinic jerking of an extremity
No loss of consciousness

A

Simple partial

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7
Q

Name that seizure!

Focal
Longer (<2 min)
Altered or loss of consciousness
Temporal lobe
Automatic movements
A

Complex partial

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8
Q

Name that seizure!

Starts focal —> general
Loss of consciousness
Muscle contractions alternating with relaxation

A

Partial with secondary generalized tonic-clonic

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9
Q

Name that seizure!

Arise from reciprocal firing of thalamus and cortex

A

Generalized seizures

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10
Q

Name that seizure!

Initial tonic rigidity (15-30s)
Subsequent tremor
Eventually clonic jerking (60-120s)
LOC
Patient stuporous and confused
A

Tonic-clonic (grand mal)

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11
Q

Name that seizure!

Sudden onset
Brief (10-30s)
Loss of awareness but not consciousness
May be some mild clonic movements

A

Absence (petit mal)

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12
Q

Name that seizure!

Brief spasm or rigidity
Often secondary to other seizure disorders

A

Myoclonic

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13
Q

Name that seizure!

Sudden loss of postural tone
Patient can fall done

A

Atonic

No drugs - they have to wear a helmet

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14
Q

What are the two targets for anticonvulsant medications?

A

Increase GABA activity (b/c blockade of GABA receptors causes seizures)

Decrease excitatory glutamate activity (b/c activation of glutamate NMDA receptors can lead to seizures)

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15
Q

Mechanisms for increasing GABA activity for the treatment of seizures

A

Block GABA reuptake (Tiagabine)

Inhibit GABA metabolism (Vigabatrin)

Stimulate GABA-a receptors (Benzos and barbs)

Bind to synaptic vesicular protein SV2A (Levetiracetam)

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16
Q

Mechanisms for decreasing glutamate activity for the treatment of seizures

A

Common targets: Voltage-gated Na+ and Ca2+ channels (Phenytoin, ethosuximide)

Other targets: SV2A, K+ channels, NMDA and AMPA receptors

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17
Q

To treat absence seizures, drugs need to target…

A

Ca2+ channels

Ethosuximide is really the only drug that does

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18
Q

How does inhibition of Na+ channels work to treat seizures?

A

Voltage gated Na+ channels become inactive after each firing

Inactivation state is prolonged so the action potential does not fire as rapidly

Targets rapidly firing neurons

No effect on normal neurons

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19
Q

Where do drugs that inhibit Na+ channels to inhibit glutamate activity bind?

A

INTRAcellularly (have to cross the membrane)

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20
Q

What are the general principles to remember for anticonvulsant therapy?

A

Most drugs will stop seizures without side effects - 50% of patients

Monitor plasma drug levels and use SINGLE DRUG if possible

Common side effects - GI, CNS disturbances
• Teratogenic
• Hypersensitivity (Stevens-Johnson syndrome)

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21
Q

Most anticonvulsant drugs are metabolized by CYP450s but these three INDUCE CYP450s

A

Phenytoin

Carbamazepine

Phenobarbital

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22
Q

What is the main difference between Phenytoin (Dilantin) and Fosphenytoin (Cerebyx)?

A

Phenytoin is not injectable (not water soluble)

Fosphenytoin is injectable

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23
Q

Uses for Phenytoin and Fosphenytoin

A

Partial seizures and generalized tonic-clonic seizures

NOT effective for absence seizures

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24
Q

Phenytoin/Fosphenytoin MOA

A

Prolongs the inactivation of Na+ channels to decrease glutamate activity

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25
Phenytoin and Fosphenytoin are elimated by ______ kinetics at low doses but ______ at therapeutic and high doses
1st order Zero order Because of this, small changes in dose/elimination can cause BIG changes in plasma levels
26
Phenytoin is likely to have interactions with...
Drugs that alter CYP450s It is metabolized by, induces, AND inhibitors CYP450s!
27
Side effects of phenytoin
Nystagmus, diplopia, ataxia, sedation GINGIVAL HYPERPLASIA*** Long term: • Coarsening of facial features • Mild peripheral neuropathy • Abnormal vitamin D metabolism Skin rash - d/c!!! (Risk of SJS)*** Pregnancy Category D
28
What are the primary uses for Carbamazepine (Tegretol)
DRUG OF CHOICE for PARTIAL seizures**** Generalized tonic-clonic seizures Bipolar disorder TRIGEMINAL NEURALGIA
29
Carbamazepine (Tegretol) increases metabolism of ...
Multiple anticonvulsants Haloperidol*** Oral contraceptives***
30
Metabolism of Carbamazepine (Tegretol) is increased by _________ and inhibited by __________
Phenobarbital, Phenytoin Cimetidine, fluoxetine, and VALPROIC ACID
31
Side effects of Carbamazepine (Tegretol)
Diplopia, ataxia, GI upset, drowsiness Aplastic anemia and agranulocytosis ***Highest potential for STEVENS JOHNSON SYNDROME*** of the anticonvulsants Pregnancy Category D
32
Patients with _________ are more likely to develop Stevens Johnson Syndrome when taking Carbamazepine
HLA-B 1502 Genetic screening is REQUIRED prior to prescribing
33
MOA for Lamotrigine (Lamictal)
Inactivation of Na+ channels; decreases glutamate activity May also inhibit Ca2+ channels
34
Uses for Lamotrigine (Lamictal)
Partial seizures**** May be effective against myoclonic and absence seizures in children Bipolar disorder
35
What pharmacokinetic details do we need to know about Lamotrigine (Lamictal)?
Inducers of CYP450s (phenytoin, carbamazepine, phenobarbital) will increase metabolism Half-life double by valproic acid
36
Side effects of Lamotrigine (Lamictal)
CNS - dizziness, HA, diplopia, ataxia, somnolence GI - nausea and vomiting Skin rash and Stevens-Johnson Syndrome Pregnancy Category C (better than the others but still not good)
37
How is Topiramate (Topamax) used?
Partial and generalized tonic-clonic seizures May also be effective for absence seizures Migraine prevention***
38
MOA for Topiramate (Topamax)
Blocks Na+ channels and decreases glutamate activity Also has some activity at Ca2+ channels Potentialities GABA receptors and inhibits glutamate receptor May inihibit spread of seizures
39
Topiramate (Topamax) may increase metabolism of ________.
Contraceptives
40
Side effects of Topiramate (Topamax)
Dizziness, sedation, nervousness, confusion ACUTE MYOPIA/GLAUCOMA
41
Uses for Levetiracetam (Keppra)
Partial, myoclonic, and tonic-clonic seizures
42
MOA for Levetiracetam (Keppra)
Binds synaptic vesicular protein (SV2A) —> decreased glutamate and increased GABA release
43
Pharmacokinetics for Levetiracetam (Keppra)
Oral absorption is rapid - peak blood concentrations in 1-2h 1/2 life of 6-8h, longer in elderly
44
Side effects of Levetiracetam (Keppra)
Dizziness, somnolence, ataxia, and asthenia
45
__________ has minimal drug interactions so is a good option for multidrug therapy
Levetiracetam (Keppra)
46
MOA for Phenobarbital (Luminal)
Prolongs opening of chloride channel at GABA receptor —> alters Na+ and Ca2+ conductance at high concentrations
47
Uses for phenobarbital (luminal)
Partial seizures Generalized tonic-clonic seizures Potential for abuse those so use with caution
48
Phenobarbital _______ CYP450s
Induces —> increased metabolism of phenytoin and carbamazepine
49
Uses for Gabapentin (Neurontin)
ADJUNCT for partial and generalized tonic-clonic seizures Neuropathic pain**** Bipolar disorder (off label)
50
MOA for Gabapentin (Neurontin)
GABA analog*** May augment GABA release
51
Pharmacokinetics of Gabapentin (Neurontin)
1st order elimination by the kidneys Short half-life, taken 3x/day
52
Side effects of Gabapentin
Sleepiness, dizziness, ataxia, fatigue, tremor, H/A Pregnancy Cat C
53
_______ has negligible drug interactions, so it’s a good 2nd drug for multidrug therapy
Gabapentin
54
What is Pregabalin (Lyrica) and how is it used?
GABA analog - structurally related to GABA Binds to alpha-2-delta subunit of voltage-gated Ca2+ channels inhibiting excitatory neurotransmitter release Used for generalized anxiety disorder*** Other uses: neuropathic pain, fibromyalgia, post-op pain
55
Side effects of Pregabalin (Lyrica)
Peripheral edema, dizziness, fatigue, weight gain, xerostomia***, ataxia, blurred vision, GI disturbances TERATOGENIC
56
Adjunct treatment for partial seizures that works by inhibiting reuptake of GABA (GAT-1) to enhance GABA activity
Tiagabine (Gabitril)
57
Side effects of Tiagabine (Gabitril)
Nervousness, difficulty concentrating, depression Dizziness, tremor, rash (rare but d/c if happens) Pregnancy Cat C
58
How is Vigabatrin (Sabril) used?
Refractory complex partial seizures Infantile spasm (West’s syndrome)
59
MOA for Vigabatrin (Sabril)
IRREVERSIBLY inhibits GABA transaminase (GABA-T) to decrease GABA metabolism and enhance activity Short half-life but b/c of MOA drug effects are prolonged and do not correlate with plasma levels
60
Side effects of Vigabatrin (Sabril)
Visual field problems and retinal damage**** Agitation, confusion
61
Drug of choice for absence seizures
Ethosuximide (Zarontin)
62
MOA for Ethosuximide (Zarontin)
Inhibits low-threshold (T-type) Ca2+ channels Inhibits ‘pacemaker’ for rhythmic cortical diamanté
63
Side effects of Ethosuximide (Zarontin)
GI irritation, lethargy, fatigue, HA, dizziness HICCUPS**** Stevens Johnson Syndrome (very rare) Metabolism is inhibited by VALPROIC ACID
64
Uses for Valproic Acid (Depakene)
Absence AND general tonic-clonic seizures (MIXED seizures) Bipolar disorder Prophylaxis of migraine
65
MOA for Valproic Acid (Depakene)
Blocks Ca2+ channels and Na+ channels May enhance GABA activity
66
Pharmacokinetics for Valproic Acid (Depakene)
Absorption is prolonged by food 1/2life of 9-18h INHIBITS ITS OWN METABOLISM at low doses
67
Valproic acid inhibits metabolism of ...
Phenytoin Phenobarbital Carbamazepine
68
Side effects of Valproic Acid
Nausea, abdominal pain, heartburn, weight gain, sedation, tremor, alopecia HEPATOTOXICITY - monitoring of liver function is REQUIRED Pregnancy Cat D
69
How is Clonazepam (Klonopin) used as an anticonvulsant?
Absence seizures, myoclonic seizures, and infantile spasms (West Syndrome)
70
MOA for Clonazepam (Klonopin)
It’s a Benzo Stimulates GABA receptor and enhances GABAergic inhibition
71
Side effects of Clonazepam (Klonopin)
Sedating Tolerance to anti-seizure effect Pregnancy Cat D
72
Drug of choice for Status Epilepticus
Diazepam (Valium) and Lorazepam (Ativan) Both are benzos
73
MOA for benzos
Stimulates GABA channel
74
All the anticonvulsants have some degree of teratogenicity but valproic acid increases the risk of ...
Spina Bifida
75
Withdrawal from anticonvulsants can lead to...
Rebound increase in seizure activity
76
Overdose of anticonvulsants
CNS depression but rarely lethal Need high drug plasma levels Respiratory depression most common effect of large overdose Do NOT treat with CNS stimulants
77
Which anticonvulsants increase the risk for Stevens Johnson Syndrome?
Drugs that block Na+ channels - Phenytoin, Lamotrigine, CARBAMEZAPINE, Valproate Patients should be screened for HLA-B 1502
78
Failure rate of contraceptives is ____ for patients on anticonvulsants versus _____ in the general population
3.1% v 0.7%
79
Birth defects are ____ as likely when on anticonvulsants as opposed to general population rate
2x Congenital heart defects and neural tube defects are most common

Pharm III Unit I (9 decks)

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