According a recent study done by researchers in Berlin, if a patient taking methotrexate (MTX) for psoriasis does not show significant improvement in after 12 weeks, then increasing dosage will most likely not improve their condition.  According to this report, the maximum dosage recommended for anyone taking MTX for psoriasis is 20 mg per week.  This weekly dose should be split up into at least two administrations to minimize immediate side effects such as nausea.

How does methotrexate work?

MTX hinders cell reproduction by blocking DNA synthesis (this is a vital part in in the cellular reproductive process).  It is especially adept at blocking hyper-proliferating cells such as those affected by psoriasis or cancer.  It is also used as an immunosuppressant to battle conditions that affect the immune system such as arthritis, Crohn’s disease or psoriasis.

How is methotrexate administered?

MTX can be administered either orally or via injection.  Taking it in pill form is most common when it is used to treat psoriasis.

Why are doctors hesitant to prescribe more than 20 mg of methotrexate per week?

MTX is also used to treat cancer, and you have probably heard of the some of the harsh side-effects that cancer treatments tend to have.   In smaller doses, which are appropriate for psoriasis patients, it still can cause some serious side effects, including long-term liver damage and drops in white blood cell counts.  The main benefit of methotrexate — that is hinders cell re-production — can also wreak havoc on other parts of the body.

What are some of the brands names used to market methotrexate?

MTX is marketed under the brand names Trexall and Rheumatrex.

A syringe filling with methotrexate solution (courtesy of Flickr):