Hi Duncan,
Often these warnings relate to the higher doses of Methotrexate used by cancer patients and the risk is more rare with the lower doses used by Lupus patients.
The problem with the drug leaflets and general information available to pharmacists and GP's who don't treat thousands of Lupus patients is that Methotrexate (and some of our other drugs) were originally developed for different uses and later found to be effective in much smaller doses for the treatment of Lupus. We 'borrow' a lot of treatments and the literature is written for their original use at much higher doses. The Rheumatologists who deal with Lupus on a daily basis realise that the interaction rate is tiny for the two drugs taken together, years of experience has taught them this.
http://www.drugdigest.org/
in the interactions section:
METHOTREXATE (in Methotrexate Tablets) may interact with IBUPROFEN (in Ibuprofen Capsules)
Although the cause of this interaction is not completely understood, ibuprofen may reduce the clearance of methotrexate from the body via the urine. If this occurs, ibuprofen may increase the risk of serious side effects or toxicity from methotrexate, especially with high doses of methotrexate that are typically used for cancer. This interaction is more rare when low doses of methotrexate are used to treat other diseases. If ibuprofen and methotrexate are used together, your doctor may want to monitor your kidney function more closely and look for signs of side effects from methotrexate.Ask your healthcare provider about these drugs and this potential interaction as soon as possible.
I also put in Naproxen and got the same warning, but interestingly enough there doesn't appear to be a problem with the well known Mobic, another NSAID, so that's something to remember if you do need pain control in the future.
Just as a side note Ibuprofen is generally not the NSAID of choice for Lupus as there are many more suitable ones in that class with a much much lower risk of side effects and allergies. I personally couldn't tolerate Ibuprofen (it actually made my symptoms worse :wink2

but I am fine with other NSAIDS. Frankly I can't function without them, I am unable to get around at all............so as with all drugs it's a risk versus benefit calculation that has to be weighed up between doc and patient.
Same with the Aspirin scenario and things like Metho...........some Lupus patients also have APS and are on Metho too. Without the Aspirin their lives are at risk from clotting events and they obviously need the Metho to help damp down their Lupus. In that scenario there is little choice.
There appears to be little in the way of interaction of acetaminophen (Panadol) and Methotrexate in the medical literature.
love
Lily