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 all decrease the effectiveness of oral contraceptives. The implication of this is that there is a higher dose of the contraceptive needed to give the same effect.
• Drugs that are safe are Valproate, Lamotrigine, Gabapentin, Levetiracetam and Vigabatrin.

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

• Yes, drugs like Valproate and Lamotrigine serum levels are decreased by contraceptives.

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

• In neonates we can see that they have a very slow metabolism of medication.
• In babies and children we see that they have a faster metabolism of these drugs than adults.
• In geriatrics we see that they should be given lower dosages because of the fact that there liver and kidney function will not be optimal.

In which cases is plasma blood level monitoring indicated?

• When using drugs like Phenytoin. This is because a small increase in phenytoin can cause a large increase in the plasma level. This is because phenytoin is metabolized with zero order kinetics and there is a constant tempo of biotransformation, irrespective of the concentration of phenytoin that is present.