Hello, As you are aware ankylosing spondylitis is a chronic disease (autoimmune) with no cure as with all autoimmune diseases. However, the disease can be very well controlled on immunosuprressive drugs such as methotrexate that you are now taking. The folic acid dose is usually 5mg taken once a week or 6 days but not on the day you take methotrexate. There are several side effects of methotrexate but none directly on sexual health or erectile dysfunction. However, if you do suffer from liver related problems due to MTX you need to stop the medication (your doctor will obviously tell you all this). Pregnant women should not take methotrexate. If you are a woman, and plan to get pregnant while on MTX, do talk to your doctor about other drugs such as azathioprine as MTX is contraindicated. I hope this answers your query as I was not clear what the question was. Best Wishes.