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?

Phenobarbitone, Phenytoin, Carbamazepine, Oxcarbazepine and Topiramate are the anti-epileptic drugs which decrease the effectiveness of the Pill. They increase the metabolism of the pill thereby making it less effective, this can lead to unwanted pregnancy. 

Valproate, Lamotrigine, Gabapentin, Leviteracetam and Vigabatrin do not affect pill metabolism and are therefore safe to us in combination with the pill. 

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

Yes they can. Oral contraceptives decrease the Lamotrigine and Valproate serum levels. Oral contraceptives can decrease the levels of anti-epileptic drugs and thus cause loss of control over seizures as well as toxicity. 

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

In neonates, the anti-epileptic of choice is Phenobarbitone, however it can cause hyperactivity.

In geriatrics, they have a decrease in renal function. This can decrease the rate of drug clearance and in turn increase the possibility of CNS toxicity. It can also cause a higher incidence of hyponatremia. 

In which cases is plasma blood level monitoring indicated?

Blood plasma monitoring is important when the patient is pregnant, or on oral contraceptives.  Furthermore, it should be monitored when undergoing therapy with the following drugs that could cause serious toxicities: phenytoin, lamotrigine, phenobarbitone, valproate, carbamazepine.