Anticonvulsants - Carbamazepine Flashcards
What is carbamazepine used for?
1) Epilepsy (1st line for focal seizures)
2) Trigeminal neuralgia
3) Bipolar disorder
How does carbamazepine work?
- inhibits neuonal sodium channels
- less action potentials fired
- inhibits spread of neuronal activity in seizure / blocks pain transmission in neuralgia.
What are the side effects of carbamazepine/
1) GI upset (nausea / vomiting)
2) Neuro (dizziness + ataxia)
3) Antiepileptic hypersensitivity syndrome (skin reaction, fever, lymphadenopathy, renal / hepatic involvement)
4) oedema
5) hyponatraemia
Who does antiepileptic hypersensitivity syndrome affect?
1 in 5000 taking carbamazepine or phenytoin within 2 months of starting treatment.
mortality of 10%
What is the result of in utero exposure to carbamezapine?
- neural tube defect
- cardiac / urinary tract abnormalities
- cleft palate
Why should carbamezapine be avoided with warfarin, oestrogens and progestogens?
- carbamezapine is an enzyme inducer.
- Warfarin, oestrogen and progestogen are metabolised by P450 enzymes.
- carbamezapine increases the activity of P450 enzymes so the drugs are broken down quicker.
- so lower concn and efficacy of these drugs when used in conjuction with carbamezapine.
Why should carbamezapines be avoided with macrolides?
Carbamezapines are metabolised by P450 enzymes.
Macrolides are cytochrome P450 inhibitors, so would lead to increased conc and efficacy of carbamezapines.
What drugs would lower the efficacy of carbamezapine?
SSRI,
tricyclic antidepressants
antipsychotics
tramadol
What is the route of adminestration of carabmazepine?
oral or rectal
What is the maximum dose of carbamezapine?
1.6g a day
How is efficacy of carbamezapine monitored?
-comparing seizure frequency before and after starting treatment
