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CNS I > CNS I Pharm - Antiepileptics > Flashcards

CNS I Pharm - Antiepileptics Flashcards

1
Q

Status Epilepticus

A

Life-threatening condition defined as either 30 minutes of continuous seizure or repeated seizures without regaining consciousness in between

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2
Q

Aura

A

Feeling or experience right before a seizure begins –> aura is indicative of a FOCUS OF SEIZURE ACTIVITY –> thus, it only occurs with PARTIAL seizures

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3
Q

Partial/Focal Seizure

A

Begins from a SINGULAR FOCUS

Can be SIMPLE (no impairment of consciousness) or COMPLEX (impairment of consciousness)

Symptoms depend entirely on the focus from which the seizure begins – motor, sensory, autonomic or psychiatric symptoms

EEG – Focal stimulation (sharp peak) and subsequent inhibition (drop after) of the surrounding neurons

Partial seizures can spread and become generalized

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4
Q

Generalized Seizure

A

No local onset - can occur secondary to a focal sometimes

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5
Q

ABSENCE Seizure

A

ABSENCE –> present with a LOSS OF ATTENTION and a JERKING OF THE EYELIDS/FACIAL MUSCLES

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6
Q

MYOCLONIC Seizure

A

Present with sudden, brief jerking of a SINGLE foot or arm, typically

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7
Q

ATONIC

A

Complete loss of muscle tone and often sudden collapse

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8
Q

TONIC, CLONIC, TONIC-CLONIC

A

Stiff (tonic), Jerky (clonic) or both (tonic-clonic) –> these are what we think of when we think of “classic” seizures

Tonic Clonic = GRAND MAL

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9
Q

Monotherapy vs. Polytherapy

A

MONO is what we want –> most patients remain seizure free from one drug

Polytherapy has minimal benefits and many more risks; BUT if it is necessary, use DIFFERENT CLASSES

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10
Q

General facts about Sodium Channel Blockers in Epilepsy

A

These drugs are NOT complete blockers of the sodium channel

They are also USAGE dependent –> high neuronal activity is required for the drugs to become active; when active, they reduce the sustained high frequency repetitive firing of APs

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11
Q

PHENYTOIN

A

Widely used sodium channel blocker

APPROVED FOR –> PARTIAL; GENERALIZED TONIC CLONIC; and STATUS EPILEPTICUS

Poor bioavailability, soluble, CYP450 metabolism (polymorphisms possible too)

Several Drug Interactions (Decreased levels with other AEDs - Carbamazepine, Phenobarbital)

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12
Q

Side Effects of Phenytoin

A

Neurological effects – ataxia, nystagmus, diplopia, SEDATION, coma

Cerebellar syndrome

Allergic rxns

Connective tissue problems

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13
Q

CARBAMAZEPINE

A

Blocks sodium channels to reduce sustained high frequency firing of APs

Also works on ACh and NMDA receptors

PARTIAL and GENERALIZED

Slow absorption, limited solubility

AUTOINDUCER of its own CYP enzyme –> more drug will cause less of an effect after using it for a while

Neuro side effects, headaches, dizziness, tics, movement disorders, allergy

Several Drug Interactions; Decreased levels with other AEDs (Phenytoin, Phenobarbital)

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14
Q

LACOSAMIDE

A

Selective enhances the SLOW INACTIVATION OF SODIUM CHANNELS (makes them more inactive)

Approved as an ADJUNCT ONLY FOR PARTIAL SEIZURES (so, not on its own)

Few drug interactions

Dizziness, ataxia, QT prolongation but not arrhythmic

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15
Q

ETHOSUXIMIDE

A

CALCIUM CHANNEL BLOCKER (only one for epilepsy)

Works on T-Type calcium channels in the thalamus, reducing low-threshold calcium currents – keeps neurons in “oscillatory” firing mode rather than “tonic”

ABSENCE SEIZURES ONLY (drug of choice)

Side Effects include dizziness, lethargy, headache, GI distress, rash, BM suppression

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16
Q

Mechanism of action for BENZODIAZEPINES

A

Thalamocortical relay neurons are acted upon by ETHOSUXIMIDE

There are GABAergic neurons projecting from the reticular nucleus of the thalamus to these relay neurons –> if these were ACTIVE, there would be a hyper polarization and an INCREASE in the low threshold calcium current - this would potentiate tonic firing and increase absence seizures

BENZOS work on GABAergic INTERNEURONS that act on those GABAergic neurons –> ENHANCE the interneurons (so they make the inhibition stronger) and they will keep those other GABA neurons from firing and there will be no tonic firing (alpha 3)

17
Q

CLONAZEPAM

A

Second line for generalized ABSENCE and MYOCLONIC

18
Q

LORAZEPAM

A

FIRST LINE FOR STATUS EPILEPTICUS

19
Q

Benzos do what, in a nutshell?

A

Essentially increase the frequency of opening of the GABA receptors (encourage inhibition) – Makes sense since the brain is hyperexcitable

20
Q

Side effects of benzos?

A

RESPIRATORY DEPRESSION, sedation, drowsiness, ataxia;

Paradoxical INCREASE in seizure frequency, tolerance after long term use

Withdrawal effects possible

Interactions with Carbamezapine, Phenobarbital (the benzos get lowered when on these other drugs - inducers)

21
Q

PHENOBARBITAL

A

Acts on GABA receptors to INCREASE AVERAGE OPEN TIME (rather than frequency of opening)

PARTIAL, GENERALIZED TONIC-CLONIC, STATUS EPILEPTICUS

Also for WITHDRAWAL states

Very long half life

Side effects – Dizziness, Ataxia, Vertigo

INCREASED by Valpro and Phenytoin

22
Q

TIGABINE

A

Increases GABA throughout the neuropil by BLOCKING GABA REUPTAKE!

Approved for PARTIAL SEIZURES

Side effects – confusion, sedation, dizziness

Levels DECREASED by carbamazepine, phenytoin, phenobarbital

23
Q

VIGABATRIN

A

Acts intracellularly to INHIBIT GABA TRANSAMINASE (degradative pathway for GABA)

Increases GABA pool for release

PARTIAL and INFANTILE SPASMS

Loss in visual functioning, sedation fatigue

24
Q

What are common side effects of all these drugs?

A

WELL, they increase GABA or potentiate its effect, so it just makes sense that SEDATION, CONFUSION, LACK OF COORDINATION, etc are all effects. CNS depression!

25
Q

LEVITERACETAM

A

Binds to a specific protein in the presynaptic terminal which MEDIATES UPTAKE OF NT INTO VESICLES – not really sure how it works

PARTIAL SEIZURES, MYOCLONIC, TONIC CLONIC

Metabolized in the KIDNEYS rather than the LIVER –> avoids a lot of side effects and drug interactions!

Brief periods of psychosis, hyperactivity and aggression are possible

26
Q

VALPROIC ACID

A

Uses all the mechanisms – BLOCKS NA CHANNELS, BLOCKS CALCIUM CHANNELS, INCREASES GABA by INHIBITING DEGRADATIVE PATHWAY

PARTIAL SEIZURES, GENERALIZED, ABSENCE, MYOCLONIC

Dose dependent protein binding, absorbed completely and rapidly

Side effects – Sedation, ataxia, tremor, hair loss, weight gain, cognitive slowing

27
Q

Biggest Side Effect of Valproic Acid?

A

TERATOGENIC IN 1% OF CASES!

28
Q

Efficacy of Anticonvulsants

A

1/3 of patients DO NOT respond to anticonvulsants!

29
Q

Absence seizures

A

Generalized seizures; looks like sleeping/daydreaming with eyelid twitches (3/sec)

Can be elicited 80% of the time in the office by asking the child to hyperventilate for 3 minutes…weird

TREATMENT of a child ONLY with ABSENCE? –> ETHOSUXIMIDE!!!!!! Calcium channel blocker

30
Q

Two best drugs for compliance?

A

CARBAMAZEPINE and PHENYTOIN (Na Channel Blockers!)

31
Q

More on Status Epilepticus

A

Prolonged and frequent seizures with sufficiently brief intervals that produce an ENDURING EPILEPTIC CONDITION

Seizures lasting longer than 30 min or more OR repeated seizures w/o a return to consciousness in between

Causes? Pre-existing epilepsy not well controlled, acute neurological insults, electrolyte imbalances, drugs, alcohol, idiopathic

Higher in young and elderly (like seizures in general and epilepsy)

SIGNIFICANT morbidity and mortality!

32
Q

Treating Status Epilepticus

A

Benzos!!!! LORAZEPAM first line!!!!! Don’t give them too fast or there will be RESP DEPRESSION

Can then add on PHENYTOIN –> monitor EKG and BP closely; can extravasate into tissues and cause PURPLE GLOVE SYNDROME which is where the fingers/hands turn dark red/purple; can be very dangerous and loss of limbs can result

Third drug to add is PHENOBARBITAL –> can cause resp depression and arrhythmias

33
Q

What is unique about Phenytoin’s metabolism?

A

Enzymes can get saturated at HIGH DOSES (non-linear kinetics) –> once this happens there is an EXPONENTIAL INCREASE in the level of drug in the blood when more is added!

Half life can be really high (no real half life) – it is dependent on dose…

34
Q

Which drug is teratogenic?

A

VALPROIC ACID silly!

CNS I (13 decks)

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