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SUM '20 - Pharm II > Week 1 Antiepileptic 2 of 4 > Flashcards

Week 1 Antiepileptic 2 of 4 Flashcards

1
Q

›Those drugs that alter synaptic function act primarily by enhancing GABA mediated neuronal inhibition:

A

–Phenobarbital: And other Barbiturates increase the duration of ion channel openings

–Benzodiazepines: increase frequency of GABA-mediated ion channel openings.

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2
Q

What delays the reuptake of GABA from synaptic clefts, effectively enhancing GABA-mediated neuronal inhibition after synaptic release of the neurotransmitter>

A

Tiagabine

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3
Q

Drug in which ›patients develop a tolerance and sedation is a common side effects?

A

Clonazepam

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4
Q

What drug is ›reserved for selected patients with uncontrolled seizures d/t its side effects?

A

Felbamate

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5
Q

What is a ›Recent benzo derivative. Unique because it does not cause significant sedation and can be used long-term d/t tolerance is relatively uncommon?

A

Clobazam

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6
Q

What drugs are used for partial seizures and has acceptable side effect profiles? (6)

A

›Drugs used for partial seizures and has acceptable side effect profiles:

–Carbamazepine

–Lamotrigine

–Oxcarbazepine

–Topiramate

–Zonisamide

–phenytoin

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7
Q

›Drugs useful for treatment of generalized seizures:

A

›Drugs useful for treatment of generalized seizures:

–Valproate

–Lamotrigine

–Topiramate

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8
Q

›Drugs effective in treatment of generalized nonconvulsive seizures and especially absence seizures:

A

›Drugs effective in treatment of generalized nonconvulsive seizures and especially absence seizures:

–Ethosuximide

–Lamotrigine

–valproate

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9
Q

What is an analog of GABA that increases synaptic GABA?

A

Gabapentin

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10
Q

What is theraputic plasma concentrations of Gabapentin?

A

2-20 mcg/mL

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11
Q

Gabapentin is ______ protein bound.

A

zero

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12
Q

Gabapentin is eliminated by?

A

renal

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13
Q

What are the uses for Gabapentin?

A

›Multiple uses:

–Anxiety

–Panic

–Major depression

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14
Q

Gabapentin has limited efficacy in ________ treatment.

A

epilepsy

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15
Q

›_________ drugs can render PO birth control less effective

A

›Antiepileptic drugs can render PO birth control less effective

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16
Q

›Seizures during pregnancy = increased ______ and ______ for mother and fetus

A

›Seizures during pregnancy = increased morbidity and mortality for mother and fetus

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17
Q

What is the goal for maternal epilepsy?

A

›Goal: Monotherapy with lowest dose to stop seizures

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18
Q

When is fetal organogenesis complete?

A

by 8th week

›Significant teratogenicity can happen if meds give in first 8 weeks

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19
Q

What are the neonatal issues with maternal epilepsy medications?

what medication has congential malformation comparable to general population?

what medication can be added during labor?

A

–Valproate and carbamazepine have more than double the risk of fetus with congenital malformations. Neural tube defects such as spina bifida may result

–Lamotrigine have rates of congenital malformation comparable to general population

–Clobazam may be added as needed especially during labor

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20
Q

›Used for patients with nonconvulsive and convulsive partial seizures. Useful in:

–Trigeminal neuralgia

–Glossopharyngeal neuralgia

A

Carbamazepine

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21
Q

›Only available PO; rapid absorption peak plasma concentrations in 2-6 hours

A

Carbamazepine

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22
Q

How much protein bound is carbamazepine?

A

70-80%

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23
Q

What is carbamazepine plasma elimination half time?

A

8-24 hours

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24
Q

›Because of Carbamazepine metabolism, increase in dosing may be needed in _________

A

2-4 weeks

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25
Q

Carbamazepine side effects?

A

›The usual side effects: sedation, vertigo, diplopia, n/v and chronic diarrhea in some patients.

›Rare side effects but can be life threatening:

–SIADH

–Aplastic anemia

–Thrombocytopenia

–Hepatocellular and cholestatic jaundice

–Oliguria

–HPTN

–Cardiac dysrhythmias

–WBC suppression

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26
Q

›High plasma concentration can have a arginine vasopressin hormone like actions resulting in hyponatremia

A

Carbamazepine

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27
Q

What happens in 10 % of pts. who take Carbamazepine?

A

skin rash

28
Q

Carbamazepine accelerates metabolism of what drugs?

A

›Accelerates metabolism of:

–Valproic acid

–Ehtosuximide

–Corticosteroids

–Anticoagulants

–Antipsychotics

29
Q

What drugs inhibit metabolism of carbamazepine sufficiently to cause toxic effects?

A

›Drugs that inhibit metabolism of carbamazepine sufficiently to cause toxic effects:

›Cimetidine

›Propoxyphene

›Diltiazem

›Verapamil

›Isoniazid

›erythromycin

30
Q

What is NOT a first line drug. Reserved for pts intractable epilepsy?

A

Felbamate

31
Q

What drug

›Used principally for poorly controlled partial and secondarily generalized seizures

A

Felbamate

32
Q

Felbamate MOA

A

›MOA unknown:

May involve NMDA, GABA, and voltage-gated calcium currents

33
Q

Felbamate pharmacokinetics?

A

›Pharmacokinetics:

–Rapid PO absorption

–Prolonged elimination half time

–Excreted unchanged by kidneys

-C-P450

34
Q

Side effects of Felbamate

A

›Side Effects:

–Aplastic anemia

–Hepatotoxicity

–Monitor CPC, Liver Functions indicated

–Metabolized by liver cytochrome P 450 so effected by concurrent meds metabolized by cytochrome P 450

35
Q

›Side Effects of what drug?

–Concomitant administration of carbamazepine or phenytoin may decrease plasma concentrations of

A

Felbamate

36
Q

What drug is long acting. Effective against ALL seizure types EXCEPT nonconvulsive primary generalized seizures?

A

Phenobarbital

37
Q

›Second-line drug treatment due to its side effects:

–Cognitive

–Behavioral

A

Phenobarbital

38
Q

›Exerts antiepileptic properties:

–Partly through potentiation of postsynaptic actions of the inhibitory neurotransmitter GABA

–Inhibition of the excitatory postsynaptic actions of glutamate

–Prolongs the duration of chloride channel opening and limits spread of seizure activity and increases the seizure threshold.

A

Phenobarbital

39
Q

PO absorption is slow but nearly complete in what drug?

A

Phenobarbital

40
Q

Peak time concentration of Phenobaribital?

A

12-18 hours

41
Q

Plasma proteing binding of Phenobarbital is ____ to ___.

A

48% to 54%

42
Q

–~ 25% is eliminated by PH-dependent renal excretion with remainder inactivated by hepatic microsomal enzymes

A

Phenobarbital

43
Q

–Principle metabolite is an inactive parahydroxyphenyl derivative excreted in urine as a sulfate conjugate.

A

Phenobarbital

44
Q

Pheno barbital –Plasma concentration of _______are usually necessary for seizure control

A

–Plasma concentration of 10-40 mcg/ml are usually necessary for seizure control

45
Q

Side effects of Phenobarbital?

A

›Side Effects:

–Sedation, irritability, hyperactivity most troublesome side effects

–Tolerance to sedation with chronic therapy

–Depression in adults, and confusion in elderly

–Megaloblastic anemia that responds to folic acid

–Osteomalacia that responds to vitamin D

–Nystagmus and ataxia with concentrations > 40 mcg/ml

–Abnormal collagen deposition causing Dupuytren (du-pew-TRNAZ) contracture may occur (mainly ring and pinky)

–Classic example of a hepatic microsomal enzyme inducer that can accelerate the metabolism of many lipid soluble drugs.

46
Q

Phenytoin is a prototype of _______

A

hydantoins

47
Q

Phenytoin is used for

A

›Effective tx of partial and generalized seizures

48
Q

Phenytoin can be given how?

A

PO and IV

49
Q

Phenytoin can be given acutely to achieve effective plasma concentration within ____ minutes.

A

20

50
Q

When giving phenytoin__________ and is not accompanied by excessive sedation

A

high therapeutic index

51
Q

MOA of Phenytoin

A

›MOA:

–Regulates sodium and possibly calcium ion transport across neuronal membranes

–This stabilizing effect on cell membranes is relatively selective for the cerebral cortex, although effect also extends to peripheral nerves

52
Q

Pharmacokinetics of Phenytoin?

A

›Pharmacokinetics

–Poor water solubility may result in in slow and sometimes variable absorption from the GI (30%-97%)

–Initial adult dose is 3-4 mg/kg. Does >500 mg rarely tolerated

–Long duration so single daily so dosage

–GI intolerance may necessitate a divided dose

53
Q

›Pharmacokinetics of Phenytoin:

–IV should not exceed ______ in adults

–Should not exceed ______ (or 50 mg/min) whichever is slower in pediatrics

–This is because of the risk of severe hypotension and cardiac arrhythmias

A

›Pharmacokinetics:

–IV should not exceed 50 mg/min in adults

–Should not exceed 1-3 mg/kg (or 50 mg/min) whichever is slower in pediatrics

–This is because of the risk of severe hypotension and cardiac arrhythmias

54
Q

Plasma concentration of phenytoin?

A

›Plasma Concentration:

–Seizure control is usual obtain with plasma concentrations of 10-20 mcg/mL.

55
Q

›Plasma Concentration of phenytoin

–For control of digitalis-induced cardiac dysrhythmias______ IV is given every 15-30 minutes until a satisfactory response or a max dose of 15 mg/kg is given

–Plasma phenytoin concentration of _______L is usually sufficient to suppress cardiac dysrhythmias

–Nystagmus and ataxia are likely with concentrations of ________

–Toxicity should be made on basis of clinical symptoms.

A

›Plasma Concentration:

–For control of digitalis-induced cardiac dysrhythmias 0.5-1.0 mg/kg IV is given every 15-30 minutes until a satisfactory response or a max dose of 15 mg/kg is given

–Plasma phenytoin concentration of 8-16 mcg/mL is usually sufficient to suppress cardiac dysrhythmias

–Nystagmus and ataxia are likely with concentrations of >20 mcg/ml

–Toxicity should be made on basis of clinical symptoms.

56
Q

Proteing binding of Phenytoin:

A

›Protein Binding:

–90% to albumin

–Greater fraction remains unbound in neonates, hypoalbuminemia and in uremic patients

57
Q

›Metabolism of Phenytoin

–98% is metabolized to the __________________appearing in urine as glucuronide. 2% unchanged in urine

–Concentrations of ________ follow 1st order kinetics and elimination half time is ~ 24 hours

–Concentrations of________ follow zero-order and the enzymes for metabolism become saturated and elimination becomes dose dependent. A relatively small increase in dose may result in dramatic increases in plasma concentration.

A

›Metabolism:

–98% is metabolized to the inactive derivative parahydroxyphenyl appearing in urine as glucuronide. 2% unchanged in urine

–Concentrations of < 10 mcg/mL follow 1st order kinetics and elimination half time is ~ 24 hours

–Concentrations of > 10 mcg/ml follow zero-order and the enzymes for metabolism become saturated and elimination becomes dose dependent. A relatively small increase in dose may result in dramatic increases in plasma concentration.

58
Q

Phenytoin side effects?

A

›Side Effects:

–CNS toxicity manifesting as: (> 20 mcg/ml)

›Nystagmus

›Ataxia

›Diplopia

›Vertigo (cerebellar-vestibular dysfunction

–Peripheral neuropathy in 30% of pts

–Gingival hyperplasia in 20% pts and is probably the most common manifestation

59
Q

principle mechanism of action Carbamazepine:

targeted seizure:

A

sodium ion channel blockade

partial seizures

60
Q

principle mechanism of action Gabapentin

targeted seizure:

A

Unknown(increases GABA release) Ch.13

partial seizure, generalized seizures

Ch. 8 acts on calcium channels and inhibts glutamate release at the dorsal horn of the spinal cord.

61
Q

principle mechanism of action phenobarbital

targeted seizure:

A

chloride ion channels

partial seizures

generalized seizures

62
Q

principle mechanism of action phenytoin:

targeted seizure

A

sodium ion channel blockade

calcium ion channel

NMDA receptors

partial seizures

generalized seizures

63
Q

principle mechanism of action Toprimate

targeted seizures

A

sodium ion channel blockade

enhanced GABA activity

glutamate antagonism

calcium ion channel blockade

partial/generalized seizures

64
Q

principle mechanism of action valproate

targeted seizures

A

sodium ion channel blocker

calcium ion channels

partial / generalized seizures.

65
Q

›Decreases frequency of seizures associated with Lennnox-Gastaut Syndrome and myotonic and atonic forms of epilepsy

which drug is this?

A

felmabate

66
Q

which drug can slow metabolism of phenytoin, phenobarbital and Valproic acid

A

Felbamate because is a potent inhibitor of P 450 enzymes,

67
Q

–If receiving Felbamate, these three drugs should be decreased by 20-30% to decrease toxicity

A

carbamazepine, phenytoin, and Valproic, dose should be decreased by 20-30% to prevent toxicity

SUM '20 - Pharm II (30 decks)

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