Methotrexate (MTX) is the drug that has helped me the most. It has helped significantly with pain, completely reduced swelling and brought me back to near-normal mobility from a point when I sometimes needed to use a wheelchair.
I had the opportunity to see this when my rheumatologist wanted to see how I did on just one of the medications I was taking - methotrexate and Enbrel. I did not take methotrexate for three weeks and before I'd been off of it for two weeks I started a major flare. By three weeks on Enbrel alone I had difficulty walking - my right foot is the most severely effected by PsA - and pain, stiffness and swelling in other joints: hands, feet, hips, knees, spine, my rib cage. Back on methotrexate, these symptoms went away. My rheumatologist took me off of Enbrel - I'd tried it for over three months - and I'm now at the beginning of experimenting with Humira.
All of these drugs require patience. Methotrexate, like the biologics, doesn't provide the sometimes same-day relief a person gets from a steroid. It took months for methotrexate alone to gradually improve my symptoms.
A number of well-designed studies show that when both methotrexate and a biologic are used together, PsA people get better "scores" on a wide range of ratings, including their own reports of how they feel, their doctors' evaluations of their joints, blood markers of inflammation, x-rays and/or MRI images that show what's happening, and so on.
Some people experience nausea or get a funny taste in their mouths the day after taking MTX, and some people feel fatigued. As several people have mentioned, folic acid, and/or a medication called leuflunomide can eliminate these side effects. Starting with a smaller dose of MTX and working your way up to a clinical dose gives the body a chance to adapt to whatever will be the therapeutic dose - the dose that's as much, but not more, than what you need. A lot of us take our MTX on Friday night or another night when we can arrange to do some less demanding things the next day and maybe schedule a nap.
MTX can be taken as tablets. It can also be taken as an intra-muscular injection that's no big deal to do yourself. The advantage of an I.M. dose is that it bypasses your stomach, so you get more of the drug into your system because it is not destroyed in your digestive tract. Injectable can also be the route for people with a degree of nausea that they find hard to handle, but at a high enough dose, the injectable can also cause nausea.
A big plus about MTX is that has been in use for decades. I remember that it was one of the chemotherapy drugs (in a much, much larger dose) that my father-in-law took over forty years ago. If MTX had serious long-term side effects like making you grow wings or putting people who used it at an increased risk of heart disease or cancer, that would be totally clear by now. The first biologics were approved for use in the early 1990s, and some much more recently, so less is known about their long-term effects.
Everyone is unique, but for a lot of us, it makes sense to start a treatment plan by seeing how methotrexate does for us, because it is pretty safe and very inexpensive. I think sometimes the biologics are like bright, red, shiny, new cars to some rheumatologists and some PsA people. It IS truly amazing to have drugs that actually get inside cells and reprogram them to behave themselves. If I were a rheumatologist I would probably prescribe biologics for all my patients - because they are so exciting. (Actually, I wouldn't, because I'm very conservative as far as medical matters go and believe in a phased approach.)
Good luck with your health.