7-2.a. Value of skin tests
Brajon et al.83 have reported the non-irritating
concentrations of PPI used in patch tests prepared with commercially
available forms of PPIs.In literature, there are different suggested
concentrations to perform patch test with PPIs
preparation47, but these data cannot be compared with
each other as the active PPI concentration in the final preparation is
not known. We advise that capsules always contain gastro-resistant
granules, which are difficult to be crushed and that PPI concentration
in the granules is low. In regards, Brajon et al., after diluting the
granules/tablets reduced in powder at 30% in petrolatum, demonstrated
that the final active PPI concentrations in patch tests were
esomeprazole at 2.92% (diluting Inexium® 40 mg tablet), omeprazole at
2.59% (Mopral® 10 mg capsule) and pantoprazole at 6.09% (Eupantol® 40
mg tablet).83
According to recommendations for drug patch test
preparations,84 we recommend to reduce
granules/tablets to a fine powder, dilute this material at 30% in
petrolatum, and note the final concentration of the active ingredient.
In case of PPIs that exist in injectable forms (esomeprazole and
pantoprazole), it is recommended to dilute them at 10% in petrolatum.
Positive patch tests results have been mainly reported in
DRESS.71,76 The value of SPT and İDT with delayed
readings have not been investigated in delayed reactions to PPI.
Classification into 2 PPI subgroups, the omeprazole group (omeprazole/
esomeprazole/ pantoprazole) and the structurally similar lansoprazole
group (lansoprazole/ dexlansoprazole/rabeprazole), may explain the
cross-reactivity in delayed HS. Among 16 reintroductions in 15 patients
with delayed HSRs, the cross-reactivity was studied by Lin et
al71. In 13 cases (10 MPE, 2 SJS/TEN, 1 DRESS), there
were no cross-reactions between structurally different PPIs. In 3 other
cases (1 MPE, 1 SJS/TEN, 1 DRESS), the reintroduction of PPIs belonging
to the same group as the causative PPI induced a relapse of the
reaction. Data is too scarce to make recommendations, but, these
preliminary results suggest that in cases of delayed HSRs switching to a
structurally different PPI should be considered.