EPILPESY: CARBAMAZEPINE Flashcards
Category
Category 1
High risk drug
Maintain on a specific manufacturers product (same brand or generic drug manufacturer)
What type of seizures is it used for?
1st line in focal seizures AND generalised tonic-clonic seizures.
What type of seizures should it NOT be used for?
Atonic
Clonic
Myoclonic
Exacerbates
Apart from epilepsy, what else can carbamazepine be used for?
- Adjunct in acute alcohol withdrawal
- Diabetic neuropathy
- Trigeminal neuralgia
- Bipolar
Contraindications
- Acute porphyrias
- Hx of bone marrow depression
Can carbamazepine be taken in pregancy
Yes
* Adjust dose based on Cp
* Increased risk of congenital malformations
* For any other indications it is not recommended to take whilst pregnant
Carbamazepine in breast feeding
Amount too small to be harmful
Therapeutic range
4-12 mg/L OR
20-50 micromol/L
Signs + symptoms of toxicity
IHANDBAG
* Incoordination
* Hyponatraemia
* Ataxia
* Nystagmus
* Drowsiness
* Blurred vision and diplopia (double vision)
* Arrhythmias
* GI disturbances
Side effects
MR preparations reduce the risk of SE
* Blood disorders
* Hepatotoxicity
* Hypersensitivity reactions
* Hyponatraemia
* Low vit D
* Oedema
* Rashes - SJS
Blood disorders
E.g. Leucopoenia, thrombocytopenia
Report/look out for signs of infection
* Fever
* Sore throat
* Mouth ulcers
* Unexplained bruising or bleeding
Hepatotoxicity
Dark urine
N + V
Abdominal pain
Itching
Jaundice
Hypersensitivity reactions (AHS)
Fever
Rash
Lymphadenopathy
Rash
Rash
* Reintroduce if mild
* Discontinue if recurrence
Pre-treatment screening
- Han chinese and Thai patients with HLA-B1502 allele = increased risk of Steven-Johnson syndrome
- Test for allelle
SJS
- 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
Hyponatraemia
In rare cases, can lead to water intoxication.
Dose-related side effects
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
Monitoring
- Plasma concentration
(measured after 1-2 weeks to ensure within
therapeutic range) - Manufacturer recommends:
* FBC
* LFTs
* Renal
Why does carbamazepine have so many interactions
potent INDUCER
Drugs that increase the concentration of Carbamazepine
Increased carbamazepine concentration = toxicity
Enzyme inhibitors
* Cimetidine
* Macrolides
* Fluoxetine
* Miconazole
Drugs that decrease the concentration of Carbamazepine
Decreased carbamazepine concentration = therapeutic failure
Enzyme inducers
* St. John’s wort
* Phenytoin
Drugs that antagonise the anticonvulsant effect of carbamazepine
Quinolones
Mefloquine
SSRIs
Antipsychotics
TCA and related antidepressants
Drugs that increase the risk of hyponatraemia
Aldosterone antagonists
SSRIs
TCAs
Diuretics
NSAIDs
Drugs that increase the risk of hepatotoxicity
Tetracyclines
Sulfasalazine
Sodium valproate
Methotrexate
Isoniazid
Statins
Fluconazole
Alcohol
Carbamazepine reduces the concentration of which drugs?
Carbamazepine is an enzyme inducer = reduces drug concentrations
* Warfarin
* Contraceptives/HRT
Carbamazepine in patients with hepatic impairment
Reduced metabolism in advanced liver disease - dose may need to be reduced.
Carbamazepine and vit D
- SE = low vit D
- Consider vit D supplementation
What are the
equivalent doses between the rectal route (via suppository) and the oral route for carbamazepine?
125mg supp = 100mg PO
