Dr. Irwin Lim has a new post up titled In My Hands, Methotrexate is NOT Chemotherapy. Interesting, especially in light of all the bloggers who claim that they’re on chemo for their RA.
Methotrexate has gotten a bad rap.
Expectation effect means that people will respond to a treatment the way they expect to respond. We’re all familiar with the term placebo effect. The placebo effect occurs when people perceive that they feel better because they expect a treatment to work (ie improvement on sugar pills instead of a real medicine). In contrast, a nocebo effect occurs when people perceive that they feel worse because they expect a treatment to have negative side effects (ie get worse/experience negative side effects while on sugar pills instead of real medicine). Placebo and nocebo are both examples of people responding to treatment in a way that they expect to respond.
That’s a problem for methotrexate, because mtx has a lot of bad press. If you visit any of the RA support pages, there’s quite a bit of discussion about how to deal with all the horrible side effects of this medication. Anyone reading the popular RA sites is likely to go away convinced that methotrexate will make them incapacitated with nausea and vomiting. In reality, 90% of people do not experience this side effect.
It’s important to recognize that the people spending time on those support sites are in the minority. The vast majority of people feel fine and don’t frequent those sites because they’re too busy living their lives.
Is mtx chemo? Methotrexate can be used for chemotherapy, and that contributes to its bad reputation. When we hear the word “chemo” we tend to think: nausea, vomiting, hair loss, really really sick. That can happen in chemotherapy. We need to be clear, though, that chemotherapy is defined as chemical (drug) treatment targeted at killing fast-growing tumor/cancer cells. The fact that mtx can be used as a drug to kill cancer cells doesn’t mean that it is always used that way.
That’s the case with RA. In treating RA, patients usually start out with 7.5mg once a week. In contrast, if I were being treated for acute lymphoblastic leukemia, I’d get 5.5 mg daily, and then 25 mg twice a week once I was in remission (dose is based on body surface area). If I were treated for lymphoma, the dose could be as high as 153 mg daily. Even though I’m on the maximum RA mtx dose of 25 mg weekly, I’m still taking much less than I’d need on chemo.
Even though methotrexate can be used as a chemotherapy drug, when treating rheumatoid arthritis there are no cancer cells being killed. Low-dose RA treatment doesn’t qualify as chemotherapy.
Read more about mtx, mtx dosing and body surface area.