Folic acid antagonist used in the treatment of several neoplasms and inflammatory disorders.
Anaphylactic shock: fewer than 20 cases reported.
General: anaphylactic shock.
Cutaneous: pruritus, urticaria, angioedema, cutaneous vasculitis, severe epidermal toxicity.
Respiratory: acute pneumonitis, bronchospasm.
Hematological: pancytopenia, agranulocytosis, hemolytic anemia.
Skin prick-test: with methotrexate 10 mg/ ml. One positive case (anaphylactic shock).
Intradermal test: 0,1 ml of 25 mg/ ml solution of methotrexate. One case positive complicated by syndromic reaction (anaphylactic shock).
No specific IgE found.
No specific histamine release shown.
Drug induced lymphocyte stimulation test (DLST): positive in 2 cases of pancytopenia, and one case of agranulocytosis.
IgG3 antibody in a case of hemolytic anemia.
Type I reactions: anaphylaxis, urticaria, angioedema.
Type II reactions: hemolytic anemia.
Type III reactions: acute pneumonitis, cutaneous vasculitis.
If no alternative therapy exists and there is a non life-threatening hypersensitivity reaction, re-challenge may be considered.
Most of the time (92%) there are recurrent symptoms despite premedication.
Desensitization is sometimes used (one successful case beginning with 0.1 mg up to 25 mg in 60 hours).