15B24: Exam Report
Compare and contrast the pharmacology of valproic acid and carbamazepine.
6% of candidates passed this question.
Both these agents are listed as “level B” in the syllabus pharmacopeia and as such a general understanding of each class and relevant pharmacokinetics and pharmacodynamics was expected. Most candidates had better knowledge of valproate than carbamazepine. Some description of the toxicological features for intensive care practitioners was expected.
K2iii / 15B24: Compare and contrast the pharmacology of valproic acid and carbamazepine
- Tx epilepsy
- Chronic pain
- Mood stabiliser
- Tx epilepsy
- Trigeminal neuralgia
- Bipolar disorder
Interestingly Sodium Valproate seems to limit atrial ectopic beats but not an indication for its use – used in epilepsy and psychiatric illness
Carbemazepine is used for focal and generalised seizures. C is not effective for Petit Mal, whereas Valproate is.
C is also used to Tx Schizophrenia
Benefit of additional IV route of admin for Valproic Acid
Stabilises inactive Na+ channels
Stimulates central GABA inhibitory pathways
Limits seizure propagation
CNS – anticonvulsant
CNS – antileptic
CVS – antiarrhythmic, depressing AV conduction
GU – antidiuretic effect
Rapid & complete
Oxidation & glucuronidase
t ½ B 8 – 20hrs
Metabolites excreted in urine
Chronic use = induces its own metabolism
Unconjugated metabolites excreted in urine
Valproate has some active metabolites
Carbemazepine may require dose adjustment in chronic use
Renal & liver damage
Neither of these side effect profiles looks appealing and both would need serum monitoring