Carbmazepine

Question 1

What is the mechanism of action of carbmazepine and the indication

Answer 1

MoA: inhibition of voltage gated sodium channels to thus prevent repetitive firing of action potentials

Indication: focal seizures epilepsy

Question 2

What is the therapeutic range of carbmazepine

Answer 2

4 to 12mg/L (20 to 50 micromol/litre)

Question 3

What are the warning signs of toxicity in carbmazepine

Answer 3

• Toxicity: incoordination, ataxia, double vision, blurriness, drowsiness, diarrhoea, N+V, HYPONATRAEMIA
• Blood disorders (fever, sore throat, unexplained bruising or bleeding)
• Skin disorders- mouth ulcers, rash
• Hepatic disorders like hepatitis (severe GI upset, fatigue, jaundice, dark urine)
• Anti-epileptic hypersensitivity syndrome- fever, rash, swollen lymph nodes

Question 4

What should you monitor for in carbmazepine

Answer 4

• Plasma concentration after 2 weeks to ensure it is within range
• Full blood count
• Renal and hepatic functions

Question 5

What are the implications of carbamazepine in hepatic impairment

Answer 5

Metabolism impaired in advanced liver disease

Dose may need to carbamazepine

Question 6

What are the implications of carbamazepine in pregnancy and breast feeding

Answer 6

Pregnancy: doses should be adjusted on the basis of plasma concentration monitoring

Breastfeeding: Monitor infant for any adverse effects

Question 7

What are the main drug interactions in carbamazepine

Answer 7

Enzyme inhibitors:
Increased plasma concentrations in erythromycin, clarithromycin

Enzyme inducers:
Decreased plasma concentrations with phenytoin, st johns wort

Carbamazepine is an enzyme inducer itself so it will reduce plasma concentrations of antipsychotics, corticosteroids, warfarin, SIMVASTATIN, progesteogens

Increased convulsion risk with orlistat