<prompt> Failure of OCP is caused byRifampicinNevirapinePhenytoinAH of the above  <response>: Ans-D A clinical guide to Contraception Leon speroffDrugs causing failure of OCPRifampicinRifabutinPhenytoinNevirapinePhenobarbitoneTopiramateVigabatrinCarbamazepineEthosuximideGriseofulvin 