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Critical Care Pharm > Antiepileptics > Flashcards

Antiepileptics Flashcards

1
Q

All Old Generation Antiepileptics (List)

A 
Phenytoin (Dilantin)
Fosphenytoin (Cerebyx)
Carbamazepine (Tegretol)
Ethosuxamide (Zarontin)
Valproic Acid derivatives: Sodium Valproate (Depakene) and Valproic Acid (Depakote)
Phenobarbital (Luminal)
Primidone (Mysoline)
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2
Q

GABA

A

The major inhibitory neurotransmitter

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3
Q

Indication for Phenytoin(Dilantin)

A

Primary generalized and partial seizures. NOT absence seizures.

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4
Q

Mechanism of Phenytoin(Dilantin)

A

Blocks Na+ channels associated with depolarization, depolarization and membrane stability.

Also prolongs inactive period of Na+channels to stop the rapid firing of action potentials.

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5
Q

Cardiac effects of Phenytoin (Dilantin) . dose dependent.

A

Widening of QRS.

Remember, do NOT give Dilantin for TCA overdose as they widen QRS as well.

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6
Q

Phenytoin (Dilantin) routes of administration

A

Dilantin infatabs- chewable (50mg)
Dilantin suspensions- 30mg/5ml or 125mg/5ml
capsules- 30 mg or 100mg
Injection- 50mg/ml, contains propylene glycol
No IM Injection

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7
Q

Max rate of Phenytoin (Dilantin) IV Infusion

A

50mg/minute

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8
Q

Prodrug of Phenytoin (Dilantin)

A

Fosphenytoin ( Cerebyx)

Max infusion 150mg/minute

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9
Q

Benefit of Fosphenytoin (Cerebyx)

A

no propylene glycol (tachydysrhythmias and hypotension)

can be given IM

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10
Q

Phenytoin (Dilantin) reference range

A

7-20mg/L
some say 10-20mg/L= measures both bound and the free fraction (1-2mg/L)
free fraction is the “active” form of the drug

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11
Q

Average dose of Phenytoin (Dilantin) adult and peds

A 
Adult maint (oral)=300-400mg/day PO
Pedi maint = 4-8mg/kg/day (1-2 divided doses)
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12
Q

Phenytoin (Dilantin) toxicity doses and symptoms

A

> 20mg/L=nystagmus
30mg/L=ataxia, seizures
40mg/L=lethargy, altered consciousness, coma. must protect airway.

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13
Q

Phenytoin (Dilantin) Side effects

A

Sedation, gingival hyperplasia, hirsutism, hyperglycemia, osteoporosis, teratogenicity (cat D), DRESS, megaloblastic anemia (due to folate def.)

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14
Q

Phenytoin (Dilantin) is an inducer of:

A

CYP3A4

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15
Q

Indications for Carbamazepine (Tegretol)

A

1)partial and secondarily generalized tonic-clonic seizures
2) DOC for trigeminal neuralgia
3) mood stabilizer in bipolar disorder
NOT myoclonic seizures (worsens)

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16
Q

Carbamazepine (Tegretol) Mech of Action

A

Blocks Na+ channels (similar to phenytoin)

has similar shape and is related to other antidepressants

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17
Q

Carbamazepine (Tegretol) therapeutic range

A

4-12 mg/L

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18
Q

active metabolite of Tegretol

A

10,11 epoxide.

causes induction and its own metabolism by inducing CYP3A4

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19
Q

DDI of Tegretol

A

Inducer of CYP1A2, 2B6, 2C8, 2C9, 2C19, 3A4

decreases Warfarin’s effect
causes oral contraceptive failure
erythromycin inhibits metabolism

20
Q

pharmacogenetics concern with Tegretol

A

HLA-B*1502 allele: causes a severe rash (SJS, TEN) win Han Chinese, asian populations, or people from Thailand, India, Singapore, or Malaysia
Life threatening skin reaction

21
Q

Side Effects of Carbamazepine (Tegretol)

A 
HLA-B*1502 allele skin reaction
Leukopenia - caution with BMS its
Aplastic Anemia and agranulocytosis - Black box
Hyponatremia -stimulates release of ADH
Drowsiness
fatigue
22
Q

Indications for Oxcarbamazepine (Trileptal)

A

initial or adjunct therapy for partial seizures

not ‘approved’ for bipolar but is often used as a mood stabilizer when CBZ has adverse SE

23
Q

available routes/formulations of Trileptal

A

Tablet= 150, 300 or 600 mg as either IR or XR
Suspension=300mg/5ml (contains ethanol) - don’t give with Antabuse or flagyl*

IR give without regard to food
XR should be taken on empty stomach

24
Q

Trileptal pharmacokinetics and DDI

A

Strong inducer of CYP3A4 and UDP
inhibits CYP2C19

lowers Oral contraceptives
increases levels of phenobarbital and phenytoin

25
Q

Oxcarbamazepine (Trileptal) Side Effects

A

HA, dizziness, nystagmus, blurred vision, n/v, rash, hyponatremia

less than CBZ (some cross-sensitivity)

26
Q

Eslicarbazepine (Aptiom) indications

A

usually adjunct therapy

partial onset seizures

27
Q

Eslicarbazepine (aptiom) dosing

A

400 mg tablet PO

max 1200mg/day

28
Q

eslicarbazepine (aptiom) metabolism

A

rapid metabolism by first pass effect into eslicarbazepine and oxcarbazepine

29
Q

Valproic acid derivatives indications

A 
Complex partial seizures (mono or adjunct)
status epilepticus
absence seizures
bipolar disorder
migraine prophylaxis
30
Q

Valproic acid formulations

A 
Valproic acid (Depakene, Stavzor) caps/syrup
Depakote (enteric coated tabs)-often preferred
31
Q

Valproic acid mechanism of action

A

partial Na+channel blocker

increases GABA levels by inhibiting GABA degradation

32
Q

Valproic acid reference range

A

50-125 mg/mL

toxicity starts at 150-200

33
Q

Valproic acid SE

A

GI (common): n/v/d dyspepsia
weight gain, hepatotoxicity, pancreatitis, tremors, dose dependent thrombocytopenia, teratogenicity due to folate deficiencies

*hyperammonemia (NH3+) - consider L-carnitine therapy
if asymptommatic=100mg/kg/day in 4 doses PO
if symptomatic = 100mg/kg IV (max 6g) over 30 min

then paint of 15mg/kg q4 hours over 10-30 min

34
Q

Valproic acid DDI

A 
Lamotrigine (lamictal)
Phenytoin (dilantin)
Phenobarbital (Luminal)
CBZ
ethosuximide (zarontin)
AZT (zidarvidine)
35
Q

ethosuximide (Zarontin) indications

A

ONLY pure absence seizures

not used with atypical absence seizures

36
Q

ethosuximide (Zarontin) reference range

A

60-100mcg/mL

37
Q

ethosuximide (Zarontin) SE

A 
GI Gastritis (primary)
fatigue, HA, neuropsychotic behavior
Rash (SJS)
Leukopenia (check CBC)
lupus-like syndrome
38
Q

phenobarbital (Luminal) indications

A

as an alternative for partial or generalized tonic-clonic seizures
*worsens absence seizures
usually 2nd line.
may be seen in pregnancy

39
Q

phenobarbital (Luminal) MOA

A

enhances GABA mediated inhibition by increasing Cl Channel openings: hyperpolarizes the neuron

40
Q

Phenobarbital (Luminal) dosing

A

Peds 2-8mg/kg/day in 1-2 doses

adults 90-180 mg once or 2 doses

41
Q

Phenobarbital (Luminal) reference range

A

desired 15-40mg/L

Toxic: >50mg/L= resp depression

42
Q

Clinical issues with Phenobarbital (Luminal)

A

inducer of CYP450 and UGT enzymes: DI
Sedation as main SE
can develop tolerance to phenobarb

43
Q

Primidone (Mysoline) indications

A

Same as phenobarbital

alternative for partial and generalized tonic clonic seizures

44
Q

Primidone (mysoline) metabolism

A

metabolized to PEMA (Phenylethylmalonamide) and Phenobarbital

45
Q

Primidone (Mysoline) dosing

A

adults: 750-1000 mg/day in 3-4 div doses (Max 2 g)
Peds: 10-25 mg/kg/d in 2-3 div doses

also give folic acid supplement

46
Q

Primidone (Mysoline) SE

A 
CNS depression
Sedation
Confusion
Suicidal ideation
*megaloblastic anemia: due to lowering of RBC and CSF folate levels

avoid in pregnancy

Critical Care Pharm (2 decks)

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