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PR3153 > IC7 Seizure & epilepsy II > Flashcards

IC7 Seizure & epilepsy II Flashcards

1
Q

What is the MOA of carbamazepine?

A

It is a sodium channel blocker.

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2
Q

What is carbamazepine used for?

A

It is used for:
1. Epilepsy
2. Neuropathic pain
3. Bipolar disorder

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3
Q

What are the 4 ADRs of carbamazepine?

A
  1. Drowsiness, dizziness, N&V
  2. Blood dyscrasia
  3. Hyponatremia
  4. Hypersensitivity*
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4
Q

What are the most severe hypersensitivity reactions of carbamazepine?

A
  1. SJS
  2. TEN
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5
Q

Which race has higher risk of carbamazepine induced hypersensitivity?

A

Asians have 10x higher risk than Caucasians.

This is due to the presence of HLA-B*1502

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6
Q

Apart from HLA-B*1502, what other allele have a wider range of hypersensitivity reactions with carbamazepine?

A

HLA-B*3101

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7
Q

In SG, which allele is mandatory for testing before starting pt on carbamazepine?

A

HLA-B*1502 testing is mandatory before starting pt on carbamazepine.

HLA-B3101 is optional. if pt has HLA-B1502, we still try to avoid using carbamazepine & use an alternative medcation.

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8
Q

If a patient has HLA-B*1502 and is on carbamazepine for >3 months with no severe ADR, what should we do?

A

Allow pt to continue on therapy as it is less likely that it will cause any severe ADRs.

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9
Q

What are some alternatives to carbamazepine in epilepsy treatment?

A

Levetiracetam, valproate, topiramate

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10
Q

What are the 1st generation antiseizure medications (ASM) that we need to know?

A
  1. Carbamazepine
  2. Phenytoin
  3. Phenobarbital
  4. Sodium valproate
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11
Q

For the 1st generation ASM, what are the common similarities that exist?

  1. High / low protein binding?
  2. Hepatically or renally cleared
  3. Do all of them have drug drug interactions?
A

For all 4 first generation drugs (CBZ, PB, PHT, VPA) that we need to know:

  1. They all have high protein binding, except phenobarbital with 50% protein binding
  2. They are all largely hepatically cleared
  3. They all have DDIs
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12
Q

What are the 2nd generation antiseizure medications that we need to know?

A
  1. Levetiracetam
  2. Topiramate
  3. Lamotrigine
  4. Clobazam
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13
Q

For 2nd gen ASM, what are the common similarities that exist?

(Levetiracetam, topiramate, lamotrigine, clobazam)

  1. High / low protein binding?
  2. Hepatically or renally cleared
  3. Do all of them have drug drug interactions?
A

Protein binding:
- Levetiracetam & topiramate have low protein binding
- Lamotrigine has moderate protein binding (50%)
- Clobazam have high protein binding

Renally or hepatically cleared:
- Levetiracetam (66%), topiramate (55%), clobazam (90%) are renally cleared
- Lamotrigine is 100% hepatically cleared

DDI:
- Levetiracetam has no DDI
- Lamotrigine has a few DDI
- Topiramate DDI is dose dependent
- Clobazam has DDI

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14
Q

What are the MOAs for all the 1st and 2nd generation medications that we need to know?

1st Gen:
1. Carbamazepine
2. Phenytoin
3. Phenobarbital
4. Sodium valproate

2nd Gen:
1. Levetiracetam
2. Topiramate
3. Lamotrigine

A

1st Gen:
1. Carbamazepine - Na+ channel blocker
2. Phenytoin - Na+ channel blocker
3. Phenobarbital - Ca2+ channel blocker
4. Sodium valproate - inhibits GABA, Na+ & Ca2+ channels

2nd Gen:
1. Levetiracetam - presynaptic SV2A release modulator
2. Topiramate - Na+ channel blocker
3. Lamotrigine - Na+ channel blocker

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15
Q

Which drug is the GOLD standard for focal onset epilepsy?

Focal onset seizures aka simple partial seizures - a seizure that happens while a person is awake, alert and aware of what is going on.

A

Carbamazepine

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16
Q

What are first line drugs used in GTC seizures?

A
  1. Carbamazepine
  2. Lamotrigine
  3. Sodium valproate
17
Q

What is the first line drug used in tonic or atonic?

A

Sodium valproate

18
Q

What are the 1st line drugs to use in absence seizures?

A
  1. Lamotrigine
  2. Sodium Valproate
19
Q

What are the 1st line drugs to use in myoclonic seizures?

A
  1. Levetiracetam
  2. Sodium valproate
  3. Topiramate
20
Q

What are the 1st line drugs for focal seizures?

A
  1. Carbamazepine
  2. Lamotrigine
  3. Levetiracetam
  4. Sodium valproate
21
Q

Can you name which ASM are inducers or inhibitors of CYP enzymes / transporters?

1st gen:
Carbamazepine -
Phenobarbital -
Phenytoin -
Sodium valproate -

2nd gen:
Lamotrigine -
Levetiracetam -
Topiramate -
Clobazam -

A

1st gen:
Carbamazepine - inducer
Phenobarbital - inducer
Phenytoin - inducer
Sodium valproate - inhibitor

2nd gen:
Lamotrigine - inducer
Levetiracetam - no effect , hence no DDI
Topiramate - CYP3A4 inducer & CYP2C19 inhibitor
Clobazam - inhibitor

Note that sodium valproate & clobazam the only inhibitors.

The rest are all inducers.

Topiramate is the only drug that is both an inducer and inhibitor.

22
Q

What are the 4 classes of drugs that have DDIs w ASMs?

A
  1. Antidepressants & antipsychotics
  2. Immunosuppressive therapy
  3. Antiretroviral therapy
  4. Chemotherapeutic agents
23
Q

What are the different dosage forms for phenytoin?

A
  1. Oral suspension
  2. Capsules
24
Q

Must we space apart enteral feeds & phenytoin? If yes, how long must we space them apart for?

A

Yes, we must space apart enteral feeds and phenytoin.

They are to be spaced apart every 2 hours.

25
Q

What is the PK of phenytoin?
(ADME)

A

A: phenytoin is completely absorbed w 100% bioavailability

D: 0.7 L/kg. 90% Albumin bound

M: Metabolized by CYP2C9 & CYP2C19

E: Zero order kinetics. Clearance is dependent on concentration. Clearance decreases when concentration increases

26
Q

What are the different dosage forms of sodium valproate?

A
  1. Injection
  2. Enteric coated tablet
  3. Sustained-release tablets
  4. Syrup
27
Q

What are the PK characteristics of sodium valproate?

No need to know excretion.

A

A: Oral bioavailability 100%

D: 0.15L/kg, 95% albumin bound.
*Has saturable protein-binding within therapeutic range.
At high concentrations, there is decreased protein binding.

M: Metabolized by many CYP enzymes

28
Q

What are the dosage forms for carbamazepine?

A
  1. Immediate-release tablet
  2. Controlled-release CR tablets
29
Q

What are the PK characteristics of carbamazepine?

A

A: bioavailability = 0.8

D: Highly protein bound (80%)

M: Metabolised >99% by CYP3A4. Carbamazepine undergoes autoinduction - it induces its own metabolism.

30
Q

What are the ways we can mitigate ADRs in anti seizure medications?

A
  1. Initiate at low dose & slowly titrate
  2. Avoid large dosage changes
  3. Restricting therapy to 1 drug only
  4. Adjusting the administration schedule
31
Q

What are common ADRs of antiseizure medications?

A
  1. Gingival hyperplasia
  2. Hirsutism
  3. Alopecia - hair loss
  4. Peripheral neuropathy
  5. Weight gain
  6. Anorexia, weight loss
  7. Metabolic bone disorder

Gingival hyperplasia, hirsutism, peripheral neuropathy are often associated w phenytoin use.

Metabolic bone disorder is associated w phenytoin, phenobarbital, carbamazepine

Alopecia , weight gain are often associated w sodium valproate use.

Anorexia & weight loss are associated with topiramate.

32
Q

What are the special considerations of titrating the dose for lamotrigine?

A

Dose for lamotrigine should be titrated slowly.

Risk of serious cutaneous reaction is higher w high starting doses, rapid dose escalation, and concomitant use with valproate.

When patient is taking valproate, we uptitrate the dose of lamotrigine even slower.

33
Q

Aromatic ASMs have cross-sensitivity reactions. Which of the common drugs that we have learnt are aromatic?

A

Carbamazepine
Phenytoin
Phenobarbital
Lamotrigine

34
Q

Summary slide for ASM ADRs.
Just click open the link

A

https://nusu-my.sharepoint.com/:i:/r/personal/e0725451_u_nus_edu/Documents/Pharmacy/Year%203/Y3S2/PR3153/ICs/IC7%20Seizure%20%26%20Epilepsy%20II/ADR%20summary.png?csf=1&web=1&e=hd43pm

35
Q

How can we optimise ASM treatment?

A

Using therapeutic drug monitoring (TDM).

TDM allows us to establish a patient’s therapeutic range, and identify for any toxicity.

36
Q

When can we discontinue ASM?

A

ASM discontinuation may be considered after:
1. Minimum of 2 years without seizure
2. Discussion with pt and their family.

However, pt w increased risk of seizure recurrence should wait longer than 2 years.

37
Q

List out the special populations involved in ASM.

A
  1. Women of childbearing potential
  2. Women on oral contraceptives
  3. Pregnancy
  4. Lactation
  5. Male of reproductive potential

Caution w use of ASM in women of childbearing potential as they can be teratogenic.

For women on oral contraceptives (OC), OC can lower lamotrigine’s concentration, causing breakthrough seizures

For pregnancy, levetiracetam and lamotrigine are safer options. Do NOT use valproate as it is teratogenic.

For breastfeeding, no CI have been found. In fact, all breastfeeding women are encouraged to do so.

For male w reproductive capabilities, valproate increases the risk of neurodevelopmental disorders (NDDs) in their children

38
Q

What is status epilepticus?

A

Status epilepticus - a seizure that lasts longer than 5 minutes, or having more than 1 seizure within a 5 minutes period, without returning to a normal level of consciousness between episodes.

Has long term consequences.

39
Q

What is the treatment procedurefor status epilepticus?

0-5min:
5-20min:
20-40min:
40-60min:

A

0-5min:
- stabilize the patient and prevent mortality

5-20min:
- If seizure continues, initiate benzodiazepine
- If seizure stops, provide symptomatic care

20-40min:
- If seizure continues, use IV ASM
- If seizure stops, provide symptomatic care

40-60min:
- If seizure continues, repeat IV ASM
- If seizure stops, provide symptomatic care

PR3153 (18 decks)

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