If you are a woman who uses an oral contraceptives, you should be aware that studies have shown that modafinil, one of the most commonly used medications for narcolepsy, lessens the effectiveness of the pill. Your doctor will almost certainly be aware of this.
Consequently, if you are prescribed modafinil for your narcolepsy, you should use an alternative method of contraception.
Our general resource article How is narcolepsy treated? includes a link to a Patient Information Leaflet about modafinil produced by the Pharmacy department at Guy's and St Thomas' Hospital that mentions this issue.
In general, of course, whatever form of contraception you use, you should discuss with your doctor any potential adverse effects of all your medications, both in terms of safety and effectiveness.