Clinical use of this family of analgesics was sharply curtailed due to its potentially fatal bone marrow toxicity (agranulocytosis).
Metamizol. Propylphenazone. Amidophenazone. Phenazone.
Metamizol: from 0.13% to 2.4% of cutaneous reactions.
Urticaria, angioedema (allergy).
Fixed drug eruption.
Toxic epidermal necrolysis.
Allergy contact dermatitis.
Intradermal skin-tests: positive at 0.001 to 0.01% in most patients with allergic symptoms (anaphylactic shock, urticaria).
Specific IgE (RAST) for 1 - phenyl - 2.3 - dimethyl - 3 - pyrazoline - 5 - one found in 17/19 pyrazolone sensitive patients.
Contraindicated if anaphylactic shock.
Sometimes useful in patients with asthma or urticaria.
IgE-mediated hypersensitivity: positive skin tests + specific IgE ; especially in patients with anaphylactic shock or urticaria.
Intolerance: similar mechanisms to other NSAIDs.
In patients with specific pyrazolone allergy, ascertain safe other NSAIDs.
Avoid all NSAIDs in cases of intolerance.