I was prescribed Fiorinal (butalbital/asa&caff) for severe head aches. I took a pill on Saturday night. On Tuesday I realized the pamphlet that came with my Fiorinal said it can lessen the affects of oral contraceptives. I had intercourse with my husband on Monday night. I immediately purchased Plan B on Tuesday afternoon. My question is, would the Plan B have worked after taking the Fiorinal on Saturday night? Would taking one Fiorinal be enough to affect my birth control pill?