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PCL 423 > Enzyme Inducers - Carbamazepine > Flashcards

Enzyme Inducers - Carbamazepine Flashcards

Dr. Aderemi

1
Q

Carbamazepine is a _______ derivative used as a prophylactic in chronic epilepsy therapy.

A

Iminostilbene

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2
Q

It is also used to treat _________________ and ____________.

A

Trigeminal neuralgia and bipolar affective disorder

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3
Q

At standard dose, CBZ may cause convulsion and CNS toxicity.

True or False?

A

True

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4
Q

The therapeutic range for carbamazepine is _______.

A

4-12μg/mL

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5
Q

At ________, patients may experience concentration-related adverse effects.

A

> 8μg/mL

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6
Q

Mention 7 concentration-related adverse effects of CBZ.

A

i. Nausea
ii. Vomiting
iii. Lethargy
iv. Headache
v. Diplopia
vi. Blurred vision
vii. Ataxia
viii. Incoordination

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7
Q

Concentration-related toxicity of CBZ may manifest as ________

A

Osteoporosis
Blood dyscrasias, such as aplastic anaemia and agranulocytosis.

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8
Q

CBZ treatment is discontinued when WBC is ________ and ANC is _________.

A

WBC<2500/mm3
ANC<1000/mm3

ANC is Absolute Neutrophil Count

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9
Q

CBZ causes AED hypersensitivity syndrome and cross-reactivity with other aromatic anticonvulsants such as ___________, ___________, __________ and other drugs that cause AED hypersensitivity syndrome.

A

Oxcarbazepine
Phenobarbital
Phenytoin

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10
Q

There are injectable CBZ preparations.

True or False.

A

False.

There is no injectable CBZ

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11
Q

List the available oral dosage forms of CBZ.

A
  1. Immediate-release tablet (regular: 100mg, 200mg, 300mg and chewable: 100mg)
  2. Sustained-release tablet (100mg, 200mg and 400mg)
  3. Sustained-release capsules (100mg, 200mg and 300mg)
  4. Suspension 100mg/5ml
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12
Q

Answer with True or False:

i. CBZ is an auto-inducer
ii. Its adverse effects can be seen early in dosage titration, soon after an dosage increase.

A

i. True
ii. True

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13
Q

Absorption 0f CBZ is rapid and Tmax depends on ________.

A

The dosage form

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14
Q

Provide the values for the following CBZ pharmacokinetic parameters.

Bioavailability =
Vd =
Plasma Protein binding =
Free unbound drug =

A

Bioavailability = 75-85%
Vd = 0.8-2.0L/kg
Plasma Protein binding = 75-80%
Free unbound drug = 20-25%

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15
Q

In the plasma, CBZ binds to albumin and ________

A

α1-acid glycoprotein (AGP)

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16
Q

The active metabolic product of CBZ is _________ and the protein binding is ________

A

Carbamazepine-10,11-epoxide
50%

17
Q

AGP is much higher in patients with stress, heart trauma, myocardial infarction and heart failure.

What is the effect of this on CBZ?

A

Increased CBZ binding to AGP resulting in lower free unbound drug (10-15%)

18
Q

CBZ is extensively metabolised in the liver by ______

19
Q

CBZ is a hepatic enzyme inducer and auto-inducer. As a result, drug must be titrated upward starting with _______of the desired dose and increased by a similar amount every ______ until the total desired daily dose is achieved, allowing liver enzyme induction and CBZ clearance to increase slowly over a time period of _____.

A
  • One-third to one-fourth
  • 2-3 weeks
  • 6-12 weeks
20
Q

Highlight the effect of liver cirrhosis and acute hepatitis on CBZ pharmacokinetics and dosing.

A

i. Decreased metabolism
ii. Decreased clearance
iii. Decreased plasma binding
iv. Increased Vd (due to iii.)
v. Increased free unbound drug (due to iii.)

21
Q

Highlight the effect of old age on CBZ pharmacokinetics and dosing.

A

Decreased clearance

Hence lower initial doses (100mg/day should be used)

22
Q

Highlight the effect of pregnancy and lactation on CBZ pharmacokinetic and dosing.

A

There is decreased CBZ clearance in 3rd trimester
Thus dosage adjustment is required.

Breast milk conc is 60% of serum conc.

23
Q

Renal failure does not warrant dosage adjustment of CBZ.

True or False?

24
Q

CBZ is a potent inducer of hepatic drug metabolizing enzyme systems and P-glycoprotein.

True or False?

25
Q

Hepatic metabolic enzymes induced by CBZ include:

A

i. CYP 3A4
ii. CYP 2C9
iii. CYP 1A2

26
Q

Induction of CYP3A4 results in the acceleration of metabolism of concurrently prescribed
anticonvulsants, such as ________.

A

i. Valproic acid
ii. Clonazepam
iii. Ethosuximide
iv. Lamotrigine

27
Q

CBZ increases clearance and decreases steady-state concentrations of many other drugs including:

A
  1. Oral contraceptives
  2. CCBs
  3. TCAs
  4. Warfarin
  5. Theophylline
  6. Cyclosporine
  7. Tacrolimus
28
Q

Mention 5 drugs that inhibit metabolic enzymes and cause CBZ toxicity.

A
  1. Cimetidine
  2. Macrolides
  3. Azole antifungals
  4. Diltiazem
  5. Fluoxetine
  6. Verapamil
  7. Indinavir
  8. Ritonavir
29
Q

Mention 2 drugs that may increase CBZ clearance and reduce Css.

A
  1. Phenytoin
  2. Phenobarbital
30
Q

How do you minimise CBZ interactions?

A
  • Avoid polypharmacy
  • Select drugs with lower potential for interaction
  • Adjust dosage based on serum concentration monitoring

PCL 423 (10 decks)

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