NERVOUS SYSTEM: CARBAMAZEPINE

Question 1

CARBAMAZEPINE: INDICATIONS

Answer 1

• Epilepsy
• Trigeminal Neuralgia
• Bipolar Disorder

Question 2

CARBAMAZEPINE: MOA

Answer 2

• Inhibit neuronal channels, stabilising resting potentials and reducing neuronal excitability

Question 3

CARBAMAZEPINE: ADVERSE EFFECTS

Answer 3

• GI upset ( nausea, vomiting)
• Neurological symptoms (dizziness and ataxia)
• HS rxns = 10% of individuals, mild maculopapular rash
• Antiepileptic hypersensitivity syndrome
• Clinical features include severe skin reactions (e.g. Stevens–Johnson syndrome, toxic epidermal necrolysis), fever and lymphadenopathy with systemic (e.g. haematological, hepatic, renal) involvement and mortality of about 10%.
• Other common adverse effects include oedema and hyponatraemia due to an antidiuretic hormone-like effect.

Question 4

CARBAMAZEPINE: WARNINGS

Answer 4

• Neural tube defects, cleft palate and urinary tract abnormailities
• Pregnant patients should take high dose folic acid with
• Hepatic, renal or cardiac disease
• Antiepileptic hypersensitivity syndrome

Question 5

CARBAMAZEPINE: INTERACTIONS

Answer 5

• Carbamazepine induces cytochrome P450 enzymes, reducing plasma concentration and efficacy of drugs that are metabolised by P450 enzymes (e.g. warfarin, oestrogens and progestogens)
• Carbamazepine is itself metabolised by these enzymes, so its concentration and adverse effects are increased by cytochrome P450 inhibitors (e.g. macrolides)
• Complex interactions occur with other antiepileptic drugs as most alter drug metabolism
• The efficacy of antiepileptic drugs is reduced by drugs that lower the seizure threshold (e.g. SSRIs, tricyclic antidepressants, antipsychotics, tramadol).