Methotrexate is often the first line DMARD prescribed to treat PsA for the simple reason that it is cheap. Most insurance companies will not authorize the more expensive, and more effective, biologic DMARDs unless and until you have a failure of therapy on the less expensive drugs. And, while Methotrexate can be effective, most people with PsA have had to move on to TNF inhibitors like Enbrel or Humira, sometimes in combination with Methotrexate, and even beyond that to the newer biologic DMARDs. So, keep a log of your disease activity, side effects of the medication, any observations you feel demonstrate the medicine's efficacy or lack thereof, and keep your Rheumatologist informed of your progress. Most importantly, recognize that this disease can be stubbornly resistant to treatment, and it might take awhile to find the most effective treatment or combination of treatments. Good luck, and visit here often.