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PHARMACOLOGY > ANTICONVULSANTS > Flashcards

ANTICONVULSANTS Flashcards

1
Q

Define
1) Seizure
2) Fit / Convulsions
3) Epilepsy

A

1) A seizure is a sudden uncontrolled electrical disturbance that manifests either as motor , sensory or even psychic
2) Fit / convulsion - seizures that manifests as motor activity
3) Epilepsy - when seizure attacks are chronic

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2
Q

Give the classification of anticonvulsants

A

Hydantoins
Iminostilbenes
Barbiturates
Benzodiazepines

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3
Q

Give two examples of Iminostilbenes

A

Carbamazepine and Oxcarbazepine

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4
Q

Give the structure of carabmazepine

A

It is a dibenzazepine - two benzene rings fused to an azepine group

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5
Q

Give the moa of carbamazepine

A

It is a sodium channel blocker

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6
Q

Sodium channels exist in which three states

A

Closed (resting)
Open
Inactivated

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7
Q

Sodium chanels are multimeric complexes composed of which subunits

A

a - has four homologous repeats
b - two auxiliary units

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8
Q

Carbamazepine blocks sodium channels during which state

A

The inactivated state

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9
Q

Give two aspects of carbamazepine that enable it preferentially inhibit action potentials during seizure and less interfere with ordinary ongoing action potential

A

Use dependence and Voltage dependence

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10
Q

Explain
1) use dependant blocking action
2) voltage dependant blocking action

A

Carbamezapine has use dependant blocking action as it effectively blocks high frequency action potentials than low frequency action potentials due to more accumulation of the action potentials during high frequency firing.

They are also voltage dependant as most sodium channels exist in the inactivated state thus alows for more blocking at this voltage

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11
Q

Give and explain advantages of using carbamezapine in seizures

A

They are both voltage and use dependant thus prevent occurrence of seizures without causing unacceptable neurological impairment

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12
Q

State the effects of carbamezapine and food.

A

Giving carbamezapine after meals slows its absorption and reduces peak levels thus enables patients to tolerate high doses

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13
Q

State a unique feature in regards to carbamezapine and its metabolism

A

It is able to induce its own metabolism causing the serum concentrations to fall after a few weeks of trearment.

During the first week a half life of abput 36 hrs is seen but drops to about 8-12hrs in patients receiving continuous treatment

Dose adjusments are thus required during the first weeks of treatment

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14
Q

Carbamezapine is metabolized in which organ and to what metabolite and by which enzyme(s)

A

Liver
carbamezapine -10,11- epoxide
Mainly CYP3A4 but CYP3A5 and CYP2C8 may assist

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15
Q

Give PK of Carbamezapine

A

1) Volume of distribution is low at 1L/Kg
2) Plasma binding is ~ 70%
3) Metabolized in the liver by CYP3A4 and able to induce its own metabolism.
5) Only 5% is excreted unchanged

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16
Q

Give the clinucal uses of Carbamezapine , atleast four

A

1) Treatment of focal seizures
2) Treatment of focal to bilateral tonic clonic seizures
3) Trigeminal and glossopharyngeal neuralgia
5) Mania in bipolar disorder
6) Treatment of GTCS but should be used with caution as it may exacerbate absence and myoclonuc seizures

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17
Q

Give AEs of Carbamezapine

A

1) Diplopia - occurs first and may last less than an hour
2) Ataxia
3) Blurred vision
4) Git discomfort
5) Sedation at high doses
6) Benign leukopenia
7) SJS - especially wuth persons having HLA-B*1502 allele
8) Rash and hyponatremia - most common cause for dicontinuation

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18
Q

Gice the C/I of Carbamezapine

A

Absence seizures as it may cause increase in seizures

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19
Q

Give the structure of Oxcarbazepine

A

It is a 10 keto analogue of Carbamezapine

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20
Q

Oxcarbazepine results in an epoxide metabolite , true or false

A

False

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21
Q

The metabolites of Oxcarbazepine contribute to its activity and are termed as

A

Monohydroxy derivatives - MHDs

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22
Q

Oxcarbamezapine MHDs undergo what type of metabolism to give Dihydroxy derivative (DHD)

A

glucoronide conjugation

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23
Q

Between Carbamezapine and Oxcarbazepine which is less potent

A

Oxcarbazepine

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24
Q

Eslicarbzepine is a prodrug of

A

S(+) - licarbazepine a metabolite of Oxcarbazepine

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25
Q

Give the half life of S(+)- licarbazepine following oral administration of Eslicarbzepine

A

20-24hrs thus OD

26
Q

Lamotrigine is classified as what in terms of its srructure

A

Phenyltriazine

27
Q

Give the MOA of Lamitrogine

A

Block sodium channels

28
Q

Lamotrigine is prefeered due to

A

its high tolerability

29
Q

The main clinical use of Lamotrigine

A

Focal seizures

30
Q

As an A/E instead of sedation Lamotrigine paradoxically causes

A

insomnia

31
Q

Although well tolerated give A/ E of Lamotrigine that may occue

A

Dizziness , Diplopia , SJS , rash

32
Q

Ethosuximide is primarily used to treat which type of seizures?

A

Absence seizures

33
Q

Give the mechanism of action of ethosuximide as a succinimide

A

It is a T type calcium channel blocker in the thalamocortical neurons.

It can also block other ion channels such as Voltage dependent Na channels and the Ca dependent K channels

34
Q

Ethosuximide is not protein bound , true or false

A

True

35
Q

Give the half-life of ethosuximide.

A

40 hours . Has low clearance

36
Q

Give the metabolism of ethosuximide

A

Metabolised by hydroxylation by CYP3A4 while 20% is excreted unchanged in urine

37
Q

Give the dosage of ethosuximide

A

Due to the long half life , the drug can allow for OD but to reduce adverse GI effects it is guven BD or TDS

38
Q

Give the DDI of ethosuximide and valproic acid

A

Administration of ethosuximide with valproic acid reduces the clearance due to inhibition of ethosuximide metabolism

39
Q

Valproic acid was initially used as a

A

Solvent mixture for other antiseizure drugs

40
Q

Give the stryctyre of valproic acid

A

simple branched chain carboxylic acid

41
Q

Give the MOA od Valproic acid

A

1) Sodium channel blockade
2) Blocks NMDA receptor ( glutamate receptor)
3) Increases GABA by stimulating Glutamic acid decraboxylase for GABA synthesis and inhibiting GABA transaminase for GABA degradation

42
Q

Give the effect pf absorption of Valproic acid and food

A

Absoption is slowed

43
Q

Give the PK of Valproic acid

A

1) Rapidly absorbed after oral administration
2) Protein bound
3) 90% protein bound
4) Metabolised by CYP2C9
5) May indrrgo carrier mediated transport into and out of CSF

44
Q

Give the most common A/ E of valproic acid

A

GIT symptoms such as nausea, vomiting, abdominal pain , heartburn

45
Q

Give other A/E of Valproic acid

A

Sedation , ataxia and tremor
Acute pancreatitis
Rash
Weight hain and stimulation of appetite

46
Q

What mist be measured in valproic acid use

A

LFTS due to hepatotoxicity that is increased in children less than 2 and polypharmacy

47
Q

Use of valproic acid in 1st trimester can lead to

A

neural tube defects , CVS orofaciaal and digital abnormalities
Cognitive impairment

48
Q

Valproic acid can lead to hyperammonia that presents as

The hyperammonia is more common in patients with

A

lethargy
Genetic defects of ammonia metabolism leading to fatal encephalopathy

49
Q

Valproic acid inhibits metabolism of

A

phenytoin
phenobarbital
ethosuximide
lorazepam

49
Q

Valproic acid inhibits metabolism of

A

phenytoin
phenobarbital
ethosuximide
lorazepam

50
Q

Valproic acid reduces the clearance of

A

Lamotrigine

51
Q

Valproic acid is termed as a broad spectrum antiseizure drug and is used in the treatment of

A

GTCs
Absence and Myoclonic
partial seizures
Migraine prophylaxis and Bipolar disorder

52
Q

Give the structure of Topiramate

A

Substituted monosaccharide

53
Q

Give the MOA of Topiranate

A

1) Blocks sodium channels
2) Potentiates / increases the inhibitory effects of GABA

54
Q

Toxicity with Topiramate

A

Somnolence , fatigue , parasthesia , nervousness
Urolithiasis
Refuced verbal fluency , Conitive impairment
Acute glaucoma - withdraw drug
Congenital oral cleft formation
Weight loss
Oligohydrosis
Reduced serum bicarbonate due to inhibition of carbonic anhydrase

55
Q

Give the oxazolidinediones

A

Trimetthadione
Dimethadione
Paramethadione

56
Q

Trimethadione was used in the treatment of absence seizudes before introduction of succinimides

A

True

57
Q

Give ghe Moa of dimethadione

A

inhibiton of T type calcium channels

58
Q

Trimethadione is not protein bound

A

True

59
Q

Trimethadione undergoes what type of metabolism

A

demethylation to dimethadione that has he major anticonvulsant activity

60
Q

Give the half life of dimethadione

A

240hrs

61
Q

Give the A/ E of oxazolidinediones

A

sedation
day blindness

PHARMACOLOGY (17 decks)

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