Carbamazepine: Details

Carbamazepine.

If we find a patient on this medicine at Shands, there are several key factors to be familiar with.

I will also try to find time to later review oxcarbazepine and topiramate.

Dose

Starting dose: 200mg BID

Titration: Increase by 200mg/day until response

Maximum dose: 1600mg total/day

-When tapering off, go slowly to avoid the risk of seizure. (Reduce dose every 2 weeks to 1 month)

-Can have bipolar relapse

-Monitor the serum level of CBZ as you are titrating to avoid toxicity.

-Check level every 5-7 days when starting for 3-4 weeks (because level will go down 2/2 autoinduction)

Therapeutic range

-Prior to starting perform:

-CBC, liver function, UA, BUN

-Eye exam

-HLA-B*15:02 in asians

Different formulations

-Capsules can be swallowed or opened and sprinkled on food.

Drug Interactions

Strong CYP3A4 inducer
Can lower levels of many meds
When CBZ stopped, drug levels of other meds may increase
Check drug interaction checker (ex: uptodate) always when starting or stopping CBZ

Side effects

-Common: dizziness, drowsiness, N/V, pruritus, blurred vision/nystagmus, tinnitus, phonophobia, constipation

-Other: decreased WBC count, rash, photosensitivity, HTN, jaundice (liver injury), fever, urinary retention

-Serious: agranulocytosis/aplastic anemia, SJS/TEN, SIADH/hyponatremia, liver dysfunction

Contraception

HLA Testing

HLA genes may impact the risk of SJS/TEN
HLA-B*15:02 allele strongly associated with SJS/TEN
Testing recommended in those with Asian ancestry
HLA-A*31:01 also a risk, but less severe
Other meds
- Oxcarbazepine risk with these alleles are less
- These alleles don’t affect risk with lamotrigine
These alleles are tested for on genesight test

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