FKLG 312:

SU 4:

#Blog 7

1. Which of the anti-epileptic drugs affect the metabolism of the Pill (oral contraceptive) and what are the implications of this? Which drugs are safe to use in combination with the Pill?

Anti-epileptic drugs that decrease the effectiveness of oral contraceptives :

• phenobarbitone
• phenytoin
• carbamazepine
• oxcarbazepine
• topiramate

The implications of this are that the female patient can have an unwanted pregnancy, or the patient’s hormone levels will not be regulated as it should because of the contraceptive not reaching therapeutic effective levels to prevent ovulation. It will decrease the Pill’s effectiveness.

Anti-epileptic drugs that are safe to use with oral contraceptives:

• valproate
• lamotrigine
• gabapentin
• levetiracetam
• vigabatrin. 

2. Can oral contraceptives also affect the effectivity of the anti-epileptic drugs?

Yes, Oral contraceptives can decrease lamotrigine and valproate serum levels.

3. How does age affect the kinetics of these drugs (from neonates to old age)?

The metabolism of anti-epileptic drugs in neonates are slower than in an adult and the metabolism of these drugs in babies and children are faster than the metabolism in an adult. The metabolism of anti-epileptic drugs in geriatrics are also slower than in an adult, and you need to administer lower dosages.

4. In which cases is plasma blood level monitoring indicated?

Blood plasma blood levels are used to see how the patient’s body tolerates the medicine. The blood tests help the doctor to identify the possible allergies, interactions, infections and other abnormalities that may affect the choice of appropriate anticonvulsant medication and helps to monitor the possible drug-induced side effects. Phenytoin can be used as an example, because Phenytoin starts off with 1st order kinetics and then zero order kinetics once the plasma concentration of phenytoin is > 10 ug/ml. The drug can then accumulate and then reach a toxicity level which is very dangerous.