Carbamazepine (High risk) Flashcards
Carbamazepine a first-line option for prophylaxis of which types of seizure?
1) Generalised tonic-clonic seizures
2) Focal seizures (with or without secondary generalisation)
Carbamazepine is not recommended to be used in which type of seizures?
Absence or myoclonic seizures
Outline the Important adverse effects caused by carbamazepine
1) Dose-related and dose limiting more common at the start of treatment : GI upset (e.g. nausea and vomiting) and neurological effects (particularly dizziness and ataxia)
2) Antiepileptic hypersensitivity syndrome.
3) Oedema and hyponatraemia due to an antidiuretic hormone-like effect
1) Which drugs are more likely to cause antiepileptic hypersensitivity syndrome?
2) How soon after starting treatment does this occur and what is the main clinical feature?
1) Carbamazepine,lamotrigine and phenytoin- rarely there is cross-sensitivity between drugs.
↳for carbamazepine- cross-sensitivity reported with oxcarbazepine and with phenytoin
2) usually within 2 months of starting treatments. Severe skin reaction
Who should carbamazepine be used in caution with?
1) Prior antiepileptic hypersensitivity syndrome due to potential cross-sensitivity.(oxcarbazepine and phenytoin)
2) Carbamazepine should be prescribed with caution in patients with hepatic, renal or cardiac disease, due to increased risk of toxicity
Discuss the use of carbamazepine in pregnancy
1) Discuss treatment with a specialist and start taking high-dose folic acid supplements before conception.
2) Exposure in utero is associated with neural tube defects, cardiac and urinary tract abnormalities and cleft palate
which individuals might need to have pre-treatment screening before initiation of carbamazepine?
Test for HLA-B*1502 allele in individuals of Han Chinese or Thai origin (risk of Stevens-Johnson syndrome)
outline the important interactions associated with carbamazepine
1) Carbamazepine induces CYP P450 reducing plasma concentration and efficacy of drugs that are metabolised by CYP enzymes (e.g. warfarin, oestrogens and progestogens)
2) Carbamazepine is itself metabolised by CYP, so its concentration and adverse effects are increased by CYP inhibitors (e.g. macrolides).
3) Interacts with antiepileptic drugs (e.g. Lamotrigine) due to altered drug metabolism.
4) The efficacy reduced by drugs that lower the seizure threshold (e.g. antipsychotics, tramadol)
what are the monitoring requirements for carbamazepine?
1) Plasma concentration for optimum response 4–12 mg/litre measured after 1–2 weeks.
2) blood counts and hepatic and renal function tests not routinely necessary
can patients switch between different formulations or brands of carbamazepine?
Avoid brand switching- Bioavailibility might vary between brands
what advice should be given to patient and career regarding the use of carbamazepine?
Blood, hepatic, or skin disorders: recognise signs of blood, liver, or skin disorders. seek immediate medical attention if symptoms such as fever, rash, mouth ulcers, bruising, or bleeding develop.
