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, carbamazepine, phenytoin, oxcarbazepine and topiramate all decrease pill effectiveness and therefore should not be given to women on oral contraceptives. Rather use valproate, lamotrigine, gabapentin, leviteracetam or vigabatrin as they do not effect pill metabolism.

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

- Estrogen has a seizure activating effect, while progesterone has a seizure protective effect.

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

Neonates and  geriatrics tend to have a slow metabolism, while babies and children have a faster metabolism than adults.

In which cases is plasma blood level monitoring indicated?

- In the case of phenytoin, as the dose increases, there is saturation of metabolism and a shift from first-order to zero-order kinetics, in which a constant quantity per unit time is metabolized. A small
increase in dose can result in a large increase in concentration. In such cases, the half-life of the drug increases markedly, steady state is not achieved in routine fashion (since the plasma level continues to rise), and patients quickly develop symptoms of toxicity.