 Single centre, two-way crossover, randomised, open-label study in 20 healthy female volunteers.The volunteers received an oral single-dose of a combined contraceptive containing 30 μg ethinyloestradiol and 150 μg levonorgestrel on two occasions once as such and once after pre-treatment with an oral once daily dose of 1200 mg of BIA 2-093 for 15 days separated by a washout period of at least 3 weeks. 