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Pharmacology > ANTIEPILEPTICS > Flashcards

ANTIEPILEPTICS Flashcards

1
Q

What is epilepsy?

A

• Epilepsy is a chronic disorder characterized by
recurrent seizures.
• Seizures are finite episodes of brain dysfunction
resulting from abnormal discharge of cerebral
neurons.
• The pathophysiologic mechanisms underlying
seizure disorders are unknown.
• Seizures are still classified according to their
clinical manifestations rather than their biological
basis.

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2
Q

How are seizures classified?

A 
1. PARTIAL SEIZURES
• SIMPLE PARTIAL SEIZURES
• COMPLEX PARTIAL SEIZURES
• PARTIAL WITH SECONDARILY GENERALIZED
TONIC-CLONIC SEIZURES
  1. GENERALIZED SEIZURES
    • TONIC-CLONIC SEIZURES
    • ABSENCE SEIZURES
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3
Q

Define a simple partial seizure?

A 
• There is no loss of
consciousness.
• Often there is abnormal
activity of a single limb
or muscle group.
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4
Q

Define complex partial seizure?

A

• There is loss of consciousness.
• Motor dysfunction may involve chewing
movements, diarrhea, urination.

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5
Q

Define Partial With Secondarily Generalized

Tonic-Clonic Seizure?

A

• The partial seizure
evolves into a tonic-clonic seizure with loss of
consciousness.

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6
Q

Define generalized seizures?

A 
• No evidence of localized
onset.
• They may be convulsive
or nonconvulsive.
• There is immediate loss
of consciousness.
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7
Q

Define Absence Seizure (petit mal)

A 
• Brief, abrupt and self-limiting
loss of consciousness.
• The patient stares and
exhibits rapid eye-blinking.
• 3 Hz spike-and-wave
pattern emerges abruptly and ceases after few seconds.
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8
Q

Name 6 other generalized seizures?

A
  • ATONIC SEIZURES
  • TONIC SEIZURES
  • CLONIC SEIZURES
  • MYOCLONIC SEIZURES
  • FEBRILE SEIZURES
  • STATUS EPILEPTICUS
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9
Q

Nature and Mechanisms of Seizures, which two neurotransmitters involved?

A

• A decrease in inhibitory synaptic activity or an increase in excitatory activity might trigger a seizure.
• GABA and glutamate are the main inhibitory and
excitatory neurotransmitters, respectively.

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10
Q

Pharmacological evidence for seizures?

A

• Experimental data shows that:
• Antagonists of the GABAA
receptor trigger
seizures.
• Agonists of glutamate receptors trigger
seizures.
• Drugs that enhance GABAergic transmission
inhibit seizures.
• Glutamate receptor antagonists inhibit seizures.
• Therefore, pharmacological regulation of synaptic function can regulate the propensity
for seizures.

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11
Q

Antiepileptic Drugs: MOA

A

• The principal mechanisms of action of antiseizure
drugs involve:
• Blockade of Voltage-Gated Ion Channels
• Modulation of Synaptic Transmission

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12
Q

Drugs that Block Voltage-Gated Ion Channels in which two ways?

A
  1. Drugs that block Voltage-Gated Na+ channels

2. Drugs that block T-type Ca2+ channels

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13
Q

Drugs that Block Voltage-Gated Na+ Channels?

A
  • Principal mechanism of action of
  • Phenytoin
  • Carbamazepine
  • Lamotrigine
  • Zonisamide
  • It may contribute to the effects of
  • Phenobarbital
  • Valproate
  • Topiramate
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14
Q

Drugs that Block T-type Ca2+ Channels through which mechanism

A

• Absence seizures involve oscillatory neuronal
activity between thalamus and cortex.
• The T-type Ca2+ current governs oscillatory
responses in thalamic neurons.
• Ethosuximide and valproate inhibit this
current and are effective in absence seizures.

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15
Q

Drugs that Affect Synaptic Transmission in regards to antiepileptics?

A 
1. Drugs that enhance GABAergic
neurotransmission
(• Postsynaptically
• Presynaptically)
2. Drugs that reduce glutamatergic
neurotransmission
(• Postsynaptically
• Presynaptically)
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16
Q

Drugs that Enhance GABAergic Neurotransmission Postsynaptically?

A
  • Direct action on the GABA receptor
  • Benzodiazepines
  • Barbiturates
  • Topiramate
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17
Q

Drugs that Enhance GABAergic Neurotransmission Presynaptically?

A 
• Inhibition of the reuptake of GABA:
Tiagabine.
• Inhibition of degradation of GABA:
Vigabatrin inhibits GABA
aminotransferase.
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18
Q

Drugs that Reduce Glutamatergic Neurotransmission Postsynaptically?

A

• Phenobarbital & topiramate block glutamate receptors.

19
Q

Drugs that Reduce Glutamatergic

Neurotransmission Presynaptically

A

• Gabapentin and pregabalin decrease
glutamate release by blocking presynaptic
voltage-gated Ca2+ channels.
• Levetiracetam binds to synaptic vesicle glycoprotein 2A (SV2A). This may affect release of glutamate and GABA.

20
Q

Main drugs used for Partial and Secondarily Generalized Tonic-Clonic Seizures

A
  • The main drugs used are:
  • Carbamazepine
  • Oxcarbazepine
  • Levetiracetam
  • Zonisamide
  • Phenytoin
  • Valproate
  • Lamotrigine
  • Topiramate
  • Phenobarbital
21
Q

Main drugs used for tonic-clonic seizures?

A
  • Main drugs used include:
  • Carbamazepine
  • Oxcarbazepine
  • Valproate
  • Lamotrigine
  • Phenytoin
  • Topiramate
22
Q

Drugs used for Absence Seizures?

A

• Drugs of choice: ethosuximide and valproate.
• If tonic-clonic seizures are present valproate is
the drug of choice.
• Valproate is also preferred for atypical absence seizures.
• Lamotrigine is probably effective.

23
Q

Drugs used for Myoclonic Seizures?

A

• Valproate is the drug of choice.
• Topiramate is also used.
• Levetiracetam is approved for adjunctive
therapy.

24
Q

Drugs used for atonic seizures?

A
  • Atonic seizures are often refractory to all drugs.

* Valproate and lamotrigine may be beneficial.

25
Q

Guidelines for seizures as Febrile Convulsions?

A

• If seizures last < 15 minutes treatment is supportive.
• Seizures lasting > 15 minutes require
pharmacological treatment to prevent brain damage.
• Treatment: diazepam given IV or as a rectal solution.

26
Q

Define status epilepticus?

A

• Status epilepticus is a single seizure lasting more than 5 minutes or two or more seizures without recovery of consciousness between
seizures.
• It may be convulsive or nonconvulsive.
• The most common type, generalized tonic-clonic status epilepticus, is a life-threatening emergency.

27
Q

Status Epilepticus: Management

A

Initial therapy
phase:
IM Midazolam Or IV Lorazepam Or IV Diazepam

Second therapy
phase:
IV Fosphenytoin Or IV Valproic acid Or IV Levetiracetam

Third therapy
phase:
Repeat second therapy or
IV thiopental, midazolam,
pentobarbital, or propofol
28
Q

How are drug induced seizures controlled in non-epileptic patients?

A

• Drug-induced seizures in nonepileptic patients
may be controlled with diazepam, lorazepam or
phenobarbital.

29
Q

Which antiepileptics induce cytochrome p450?

A 
Induce cytochrome P450:
• Carbamazepine
• Phenobarbital 
• Phenytoin
• Oxcarbazepine is a weak P450 inducer
30
Q

Valproate AE?

A 
Valproate
• Hepatotoxicity.
• Inhibits cytochrome P450.
• Inhibits metabolism of several drugs.
• Inhibits its own metabolism.
31
Q

Phenytoin AE?

A 
Phenytoin
• Diplopia, ataxia.
• Gingival hyperplasia.
• Coarsening of facial features in children.
• Hirsutism.
• Rash. Stevens-Johnson Syndrome.
• Zero order kinetics of elimination.
32
Q

Carbamazepine AE?

A
  • Aplastic anemia, agranulocytosis.

* Rash. Stevens-Johnson syndrome

33
Q

Which antiepileptics induce Rash & Stevens-Johnson Syndrome
High risk:
Which has a black box warning?

A 
High risk:
• Phenytoin
• Lamotrigine
• Carbamazepine
• Phenobarbital

Lamotrigine has a black box warning:
“Lamotrigine should ordinarily be discontinued
at the first sign of rash.”

34
Q

AE of phenobarbital and primidone?

A 
Phenobarbital
• Sedation, drowsiness.
• Rash. Stevens-Johnson syndrome.
• Tolerance, dependence.
• Cognitive impairment, hyperactivity.
• P450 inducer.
Primidone
• The adverse effects of primidone are similar to
those of its metabolite, phenobarbital.
35
Q

AE of Vigabatrin?

A

Vigabatrin

• Visual field loss.

36
Q

AE of Felbamate?

A

Felbamate
• Aplastic anemia
• Hepatotoxicity
• For refractory epilepsy

37
Q

Guidelines for Discontinuing Antiepileptic Therapy

A

• If a patient is seizure-free for 3-5 years
discontinuation is warranted.
• Discontinuation should be slow.
• Benzodiazepines and barbiturates should be
discontinued very gradually to avoid withdrawal
seizures.
• If the patient is on combination therapy, drugs
should be withdrawn one at a time.

38
Q

Consequence of overdose on antiepileptics?

A

• Antiepileptic drugs are commonly taken in
intentional drug overdoses.
• Antiseizure drugs are rarely lethal.
• The most dangerous effect after large overdoses
is respiratory depression.
• Treatment is supportive.
• Stimulants should not be used.

39
Q

Are antiepileptics teratogenic, which one specifically?

A

• There is an increased risk of congenital
malformations in infants born of women taking
antiseizure drugs.
• Valproate causes a significantly higher rate of
fetal malformations compared to other
antiepileptic drugs.
• Prophylactic folic acid decreases incidence of
neural tube defects.

40
Q

What is Newborn Hemorrhagic Disease in regards to antiepileptics?

A

• Enzyme-inducing antiepileptic drugs may
increase degradation of vitamin K in the fetus.
• This can cause bleeding in the newborn infant.
• Vitamin K supplementation is recommended for
the mother in the final month of pregnancy and
for the newborn.

41
Q

Other Uses of Antiseizure Drugs?

A 
• Carbamazepine: Neuropathic pain; bipolar disorder.
• Gabapentin: Neuropathic pain.
• Lamotrigine: Bipolar Disorder.
• Pregabalin: Neuropathic pain.
• Topiramate: Migraine.
• Valproate: Bipolar disorder; migraine.
• Primidone: First line for essential tremor
(propranolol is also first line).
42
Q

Nonpharmacologic Approaches part 1 to antiepileptics?

A

• About 1/3 of patients with epilepsy continue to
have seizures on medication.
Surgery
• For most patients whose seizures originate from
a local area of abnormal brain, function improves markedly when the epileptic focus is resected.

43
Q

Non-pharmacological approaches to antiepileptic management?

A

The Ketogenic Diet
• Four parts fat to one part protein and carbohydrate.
• The high fat content and extremely low carbohydrate content produce ketosis, which appears to have a direct anti seizure effect.
• How the ketogenic diet suppresses seizures
remains unclear.

Vagus Nerve Stimulation
• Intermittent electrical stimulation of the left vagus nerve with an implanted pacemaker-like device.
• The patient can activate the device when they sense a seizure is imminent.

Pharmacology (49 decks)

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