 - Female subjects of childbearing potential who are unwilling or unable to use an appropriate method of contraception i.e. implants of levonorgestrel, injectable progesterone, an acceptable intra-uterine device IUD any IUD with a failure rate of less than 1 per year, oral contraceptives or any other method with a failure rate of 1 per year for at least two weeks prior to the first dose of study medication and should continue using the same contraceptive measure until the final pregnancy test has been performed not less than 72 hours after treatment. Alternatively they may be surgically sterilised refer to section 6.4 or remain abstinent for 2 weeks before exposure to study drug. 