EPILPESY: CARBAMAZEPINE Flashcards

1
Q

Category

A

Category 1
High risk drug

Maintain on a specific manufacturers product (same brand or generic drug manufacturer)

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2
Q

What type of seizures is it used for?

A

1st line in focal seizures AND generalised tonic-clonic seizures.

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3
Q

What type of seizures should it NOT be used for?

A

Atonic
Clonic
Myoclonic
Exacerbates

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4
Q

Apart from epilepsy, what else can carbamazepine be used for?

A
  • Adjunct in acute alcohol withdrawal
  • Diabetic neuropathy
  • Trigeminal neuralgia
  • Bipolar
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5
Q

Contraindications

A
  • Acute porphyrias
  • Hx of bone marrow depression
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6
Q

Can carbamazepine be taken in pregancy

A

Yes
* Adjust dose based on Cp
* Increased risk of congenital malformations
* For any other indications it is not recommended to take whilst pregnant

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7
Q

Carbamazepine in breast feeding

A

Amount too small to be harmful

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8
Q

Therapeutic range

A

4-12 mg/L OR
20-50 micromol/L

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9
Q

Signs + symptoms of toxicity

A

IHANDBAG
* Incoordination
* Hyponatraemia
* Ataxia
* Nystagmus
* Drowsiness
* Blurred vision and diplopia (double vision)
* Arrhythmias
* GI disturbances

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10
Q

Side effects

A

MR preparations reduce the risk of SE
* Blood disorders
* Hepatotoxicity
* Hypersensitivity reactions
* Hyponatraemia
* Low vit D
* Oedema
* Rashes - SJS

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11
Q

Blood disorders

A

E.g. Leucopoenia, thrombocytopenia
Report/look out for signs of infection
* Fever
* Sore throat
* Mouth ulcers
* Unexplained bruising or bleeding

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12
Q

Hepatotoxicity

A

Dark urine
N + V
Abdominal pain
Itching
Jaundice

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13
Q

Hypersensitivity reactions (AHS)

A

Fever
Rash
Lymphadenopathy

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14
Q

Rash

A

Rash
* Reintroduce if mild
* Discontinue if recurrence

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15
Q

Pre-treatment screening

A
  • Han chinese and Thai patients with HLA-B1502 allele = increased risk of Steven-Johnson syndrome
  • Test for allelle
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16
Q

SJS

A
  • Due to carbamazepine
  • Rare but serious
  • Circular patches can occur characterised by darker in the middle and lighter on the outside
    1. Flu
    2. Rash upper body -> spreads
    3. Blisters + sores can occur on lips, genitals and eyes
17
Q

Hyponatraemia

A

In rare cases, can lead to water intoxication.

18
Q

Dose-related side effects

A

Some SE are dose-related and dose-limiting
More common at the start of treatment and in elderly patients.
* Headache
* Ataxia
* Droswiness
* N + V
* Blurred vision
* Unsteadiness
* Allergic skin reactions

19
Q

Monitoring

A
  1. Plasma concentration
    (measured after 1-2 weeks to ensure within
    therapeutic range)
  2. Manufacturer recommends:
    * FBC
    * LFTs
    * Renal
20
Q

Why does carbamazepine have so many interactions

A

potent INDUCER

21
Q

Drugs that increase the concentration of Carbamazepine

A

Increased carbamazepine concentration = toxicity
Enzyme inhibitors
* Cimetidine
* Macrolides
* Fluoxetine
* Miconazole

22
Q

Drugs that decrease the concentration of Carbamazepine

A

Decreased carbamazepine concentration = therapeutic failure
Enzyme inducers
* St. John’s wort
* Phenytoin

23
Q

Drugs that antagonise the anticonvulsant effect of carbamazepine

A

Quinolones
Mefloquine
SSRIs
Antipsychotics
TCA and related antidepressants

24
Q

Drugs that increase the risk of hyponatraemia

A

Aldosterone antagonists
SSRIs
TCAs
Diuretics
NSAIDs

25
Q

Drugs that increase the risk of hepatotoxicity

A

Tetracyclines
Sulfasalazine
Sodium valproate
Methotrexate
Isoniazid
Statins
Fluconazole
Alcohol

26
Q

Carbamazepine reduces the concentration of which drugs?

A

Carbamazepine is an enzyme inducer = reduces drug concentrations
* Warfarin
* Contraceptives/HRT

27
Q

Carbamazepine in patients with hepatic impairment

A

Reduced metabolism in advanced liver disease - dose may need to be reduced.

28
Q

Carbamazepine and vit D

A
  • SE = low vit D
  • Consider vit D supplementation
29
Q

What are the
equivalent doses between the rectal route (via suppository) and the oral route for carbamazepine?

A

125mg supp = 100mg PO