Trimethoprim (2.4-diamino-5-(3',4',5'-trimethoxybenzyl) pyrimidine) is a synthetic folate antagonist anti-infective agent used for the treatment of urinary tract infections and for Pneumocystis pneumonia in AIDS patients.
Clinical manifestations
Anaphylactic shock.
Bronchospasm, hypersensitivity pneumonitis.
Rash, pruritus, general urticaria, facial angioedema, fixed drug eruption.
Diagnostic methods
Cutaneous testing.
Skin-prick tests with trimethoprim 10 mg/ ml in glycerol.
Specific IgE
RAST TMP-HSA + RAST inhibition (TMP-HSA coupled to bis-oxirane-activated sepharose or nitrocellulose paper disks).
IgE-mediated hypersensitivity (positive cutaneous tests, specific IgE)
3 different IgE antibody binding determinants:
  • 3-4 dimethoxybenzyl group.
  • 2-4 diamino-5-(3',4'-dimethoxy-benzyl) pyrimidine group.
  • entire TMP molecule.


  1. Pham N.H, Baldo B.A, Manfredi M, Zerboni R, "Fine structural specificity differences of trimethoprim allergenic determinants", Clin. Exp. Allergy, 1996 ; 26: 1155-60
  2. Cabanas R, Caballero M.T, Vega A, Martin-Esteban M, Pascual C, "Anaphylaxis to trimethoprim", J. Allergy. Clin. Immunol, 1996 ; 97 (1.1): 137-8
  3. Harle D.G, Baldo B.A, Smal M.A, Van Nunen S.A, "An immunoassay for the detection of IgE antibodies to trimethoprim in the sera of allergic patients", Clin. Allergy., 1987 ; 17: 209-16

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.