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Pharmacology > Anticonvulsants > Flashcards

Anticonvulsants Flashcards

1
Q

What is a seizure

A

an abnormal, synchronized electrical depolarization of neurons in the central nervous system

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2
Q

name 5 major causes of seizures

A
  1. idiopathic
  2. CNS infections
  3. fever
  4. metabolic defects
  5. cerebral trauma
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3
Q

List the different types of seizures

A 
Partial (simple and complex)
Generalized tonic-clonic
Status epilepticus
absence
febrile
myoclonic
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4
Q

What is a partial (focal) seizure

A

a seizure in which abnormal discharges occur from a focal area within the brain. There are two types of partial sizers: simple and complex

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5
Q

What are the characteristics of a simple partial seizure?

A

a simple partial seizure involves a focal neurological symptom that can be sensory (for example, auditory or visual hallucinations), motor, or psychomotor. Consciousness is always retained.

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6
Q

What happens in a complex partial seizure?

A

the initial focus of abnormal discharge spreads, so that the patient experiences loss of consciousness and postictal (post seizure) confusion. Symptoms can include coordinated motor activity, mental distortion, and sensory hallucinations.

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7
Q

Where do complex partial seizures originate?

A

The majority originate in the temporal lobe

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8
Q

What part of the brain is involved in a generalized tonic-clonic (grand-map) seizure?

A

the entire cerebral cortex

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9
Q

Name & describe the typical phases of a grand-mal seizure

A

Tonic phase = loss of consciousness , rigidity, loss of bowel and bladder control
Clonic phase = jerking movements of the entire body

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10
Q

Can a partial seizure progress into a grand map seizure?

A

Yes. This is known as partial seizures with secondary generalization

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11
Q

What is status epileptics?

A

continuous seizures not separated by any periods of regained consciousness. This condition is a medical emergency

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12
Q

What are the characteristics of absence (petit map) seizures?

A

the usually occur in children 2-12 years of age. They are characterized by a very brief few seconds loss of consciousness. The child will stop whatever he or she is doing and stare or have some facial twitching. Following the attack, the child immediately becomes alert and is seldom even aware that it has occurred.

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13
Q

What are the characteristics of febrile seizures?

A

they occur in children. They usually last less than 10 minutes. The child has a fever, but there is no apparent infection or other defined cause for the seizure.

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14
Q

What are the characteristics of myoclonic seizures?

A

They are sudden, short episodes of either local or generalized muscle contractions. They can occur at any age. They are associated with a variety of rare hereditary neurodegenerative disorders

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15
Q

Define epilepsy

A

Epilepsy is a group of chronic syndromes characterized by recurrent seizures with periods of consciousness

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16
Q

What percentage of the population is affected by epilepsy?

A

about 1%

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17
Q

What are the major pharmacological treatment options for seizures?

A 
Phenytoin
Carbamazepine/oxcarbazepine
Phenobarbital
Primidone
Valproic acid
Topiramate
Ethosuximide
Benzodiazepines
Tiagabine
Vigabatrin
Gabapentin
Lamotrigine
Zonisamide
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18
Q

What are the therapeutic use of phenytoin?

A

Phenytoin is effective in treating tonic-clonic seizures and partial seizures but NOT absence seizures. It is also used in the treatment of status epileptics after the preliminary administration of diazepam.

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19
Q

What is the MOA of phenytoin?

A

Phenytoin binds to Na+ channels and prolongs their inactivated state.

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20
Q

Describe the absorption & metabolism of phenytoin

A

Oral absorption is slow. Phenytoin undergoes hydroxylation by the hepatic cytochrome450 system. At high doses, the hydroxylation system becomes saturated; it is therefore important to watch for toxicity

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21
Q

What are the toxic effects of phenytoin?

A

Gingival hyperplasia
Diplopia, nystagmus
Megaloblastic anemia secondary to interference with folate metabolisms
Hirsutism
Diminished deep tendon reflexes in the extremity
CNS depression
Endocrine disturbances - diabetes insipidus, hyperglycemia, glycosuria, osteomalacia

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22
Q

Name 3 drugs that increase the plasma concentration of phenytoin.

A
  1. Chloramphenicol
  2. Isoniazid
  3. Cimetidine
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23
Q

Name one drug that is well known to decrease the plasma concentrations of phenytoin.

A

Carbamazepine

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24
Q

Is phenytoin taratogenic?

A

yes. it produces fetal hydantoin syndrome, which is characterized by prenatal growth deficiency & mental deficiencies. There is also an increased incidence of congenital malformations, such as cleft palate and heart malformations.

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25
Q

What is the therapeutic use of carbamazepine?

A

it is the drug of choice for treating partial and tonic-clonic seizures. It is also the drug of choice for treating trigeminal neuralgia.

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26
Q

What is the mechanism of action of carbamazepine?

A

prolongs the inactivated state of Na+ channels.

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27
Q

What are the absorption & metabolism of the drug?

A

Carbamazepine is absorbed slowly when given oral an dis metabolized by the P-450 system.

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28
Q

Which drugs inhibit the metabolism of carbamazepine?

A 
Erythromycin
Isoniazid
Propoxyphene
Verapamil
Cimetidine
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29
Q

What are carbamazepines adverse effects?

A

Acute intoxication can lead to respiratory depression, stupor, or coma.
Severe liver toxicity. Patients need frequent liver function tests while receiving this drug.
Aplastic anemia
Agranulocytosis
Patients frequently complain of drowsiness, ataxia, nystagmus, and vomiting.

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30
Q

How does oxcarbazepine differ from carbamazepine?

A

Oxcarbazepine has a slightly different chemical structure than carbamazepine, which helps minimize its side effects. Oxcarbazepine also does not induce the cytochrome P-450 system as much as carbamazepine. It does, however, have a mechanism of action & anti epileptic carbamazepine.

31
Q

What is the classification of Phenobarbital (Luminal)?

A

it is a barbituate

32
Q

MOA of Phenobarbital (Luminal)?

A

Potentiation of GABA-mediated synaptic inhibition. The mechanism of action is not completely clear, but it is thought to prolong the opening of Cl- ion channels.

33
Q

What are phenobarbitals therapeutic uses?

A
  1. It is the drug of choice for treating febrile seizures; it is also used to treat grand-mal seizures in children.
  2. It is good for treating parietal seizures and tonic-clonic seizures; however, its sedative effects have reduced its use as a primary agent.
34
Q

How is phenobarbital absorbed & metabolized?

A

The drug is well absorbed orally; 75% of it is metabolized in the liver. It is a potent inducer of the cytochrome P-450 system. The metabolic by-products are excreted in the urine.

35
Q

State phenobarbitals adverse effects.

A

Sedation
Nystagmus
Psychotic reactions
Hypersensitivity reactions - Steven Johnson syndrome

36
Q

What drug is primidone (mysoline) structurally related to?

A

It is related to phenobarbital and it works the same way as phenobarbital.

37
Q

When is primidone (mysoline) used?

A

Primidone is an alternative choice for adults who have parietal seizures (both simple and complex) and generalized tonic-clonic seizures.

38
Q

How is Primidone (mysoline) metabolized?

A

Primidone is converted to phenylethyl-malonamide (PEMA) and to phenobarbital in the liver.

39
Q

What are the adverse effects of Primidone (mysoline)?

A 
The drugs toxic effects are very similar to those of phenobarbital:
Sedation
Ataxia
Nausea
Vomiting
Drowsiness
40
Q

What are the indications for use of Valproic acid (Depakene)?

A

Valproic acid is the most effective agent for treating myoclonic seizures. It is also used in the treatment of absence seizures.

41
Q

How does Valproic acid (Depakene) work?

A

It prolongs the inactivated state of Na+ channels. It may also increase GABA concentrations in the brain.

42
Q

What is the route of administration of Valproic acid (Depakene)?

A

well absorbed orally. Once absorbed, approximately 90% bound to plasma proteins.

43
Q

How is Valproic acid (Depakene) metabolized?

A

The drug is extensively metabolized in the liver by the CYP-450 system. However, it does not induce the enzymes of this system, as do carbamazepine and phenytoin. Approximately 3% of the drug is excreted unchanged.

44
Q

Does valproic acid block the metabolism of other drugs?

A

Yes. It can increase the plasma levels of other drugs such as phenobarbital or phenytoin.

45
Q

What side effects should you watch for when administrating valproic acid?

A

Hepatoxicity. This drug may cause a fulminant hepatitis, which can be fatal. Therefore liver enzymes should be monitored.
GI distress; nausea and vomiting
Sedation
Tremor

46
Q

Should pregnant women be give valproice acid?

A

No! The incidence of neural tube defects is very high if this drug is taken during the first trimester of pregnancy.

47
Q

How does Topiramate (Topamax)?

A

Topiramate has several sites of action. It blocks glutamate receptors and Na+ channels. it also potentiates the action of GABA.

48
Q

When should topiramate (Topamax) be prescribed?

A

As an adjuvant in the treatment of partial or generalized tonic-clonic seizures.

49
Q

How is topiramate (Topamax)?

A

Generally the side affects are mild. They include fatigue, ataxia, and dizziness. Renal stones have also been reported. Pregnant women, however, should not use topiramate because of its teratogenic nature.

50
Q

What is Ethosuximide (Zarontin) used for?

A

Drug of Choice for treating absence seizures

51
Q

What is Ethosuximide (Zarontin) mechanism of action?

A

Inhibits Ca2+ influx through T-type channels in the Thalamic neurons

52
Q

How is Ethosuximide (Zarontin) absorbed & metabolized?

A

It is well absorbed orally. The majority of the drug is metabolized by the CYP-450 system in the liver. It does not induce P-450 enzyme synthesis.

53
Q

State the toxic effects.

A

Dizziness, Agitation, GI distress, Confusion
Blood dyscrasias such as leukopenia, aplastic anemia, and thrombocytopenia may occur in extremely sensitive patients.
Skin reactions such as Stevens-Johnson syndrome have also been reported.

54
Q

Give 3 examples of benzodiazepines that are used for anti epileptic purposes.

A
  1. Diazepam (Valium)
  2. Clonazepam (Klonopin)
  3. Clorazepate (Tranxene)
55
Q

What is the therapeutic use of Benzodiazepines?

A

Intravenous diazepam is the drug of choice for igniting treatment of status epileptics.
Clonazepam can be used for treating myoclonic or absence seizures in children.
Clorazepate may be used for partial seizures in combination with other drugs.

56
Q

State the adverse effects of benzodiazepines.

A

The benzodiazepines when used correctly, have relatively minor side effects, but you should watch for the following:
Drowsiness
Respiratory Depression
Cardiac Depression

57
Q

When would you use Tiagabine (Gabitril)?

A

For the treatment of partial seizures with or without secondary generalization.

58
Q

How does Tiagabine (Gabitril) work?

A

Increases GABA concentrations in the synapse by blocking GABA reuptake.

59
Q

What are the side effects for Tiagabine (Gabitril)?

A

Dizziness
GI upset
Tremor

60
Q

How does Levetiracetam (Keppra) work?

A

Its mechanism of action is unclear. No evidence has emerged that it works on either voltage gated channels or GABA receptors.

61
Q

When would you use Levetiracetam (Keppra)?

A

As an adjuvant for parietal seizures. It does not interact with other seizures medications & therefore is a good choice for combination therapy.

62
Q

What adverse effects does Levetiracetam (Keppra) have?

A

The most common effects include drowsiness, asthenia, and dizziness.

63
Q

State the therapeutic use of Gabapentin (Neurontin)?

A

Gabapentin is used to treat partial seizures with & without secondary generalization. This drug is used in adults in combination with other anti seizure drugs. Gabapentin has also been found useful for the treatment of neuropathic pain.

64
Q

What is the MOA of Gabapentin (Neurontin)?

A

Promote the release of GABA

65
Q

What is the metabolism of Gabapentin (Neurontin)?

A

excreted unchanged in the urine

66
Q

State the toxic effects of Gabapentin.

A

Ataxia
Somnolence
Headache

67
Q

What is the therapeutic role of Lamotrigine (Lamictal)

A

treat partial seizures, generalized tonic-clonic seizures, and absence seizures.

68
Q

What is the MOA of Lamotrigine (Lamictal)?

A

blocks sustained repetitive firing by voltage-dependent Na+ channels.

69
Q

Name the site of metabolism of Lamotrigine (Lamictal)?

A

liver

70
Q

What are the toxic effects of Lamotrigine (Lamictal)?

A

Dizziness
Blurred Vison
Rarely life-threatening skin disorders such as Steven-Johnsons syndrome and toxic epidermal necrolysis

71
Q

How does the drug compare to zonisamide?

A

Zonisamide can also cause renal stones.

72
Q

How does Zonisande (Zonegran) work?

A

blocks voltage gated Na+ channels and T-type calcium currents

73
Q

When would Zonisande (Zonegran) be prescribed?

A

as an adjustment drug in the therapy of partial seizures and generalized seizures.

74
Q

What are Zonisande (Zonegram) toxic effects?

A

Most commonly somnolence, ataxia, and headache. Rarely can cause renal stones.

Pharmacology (6 decks)

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