Pharmacokinetics of Der p 2 allergen and derived monomeric allergoid in allergic volunteers.
BACKGROUND
Presently, sublingual immunotherapy is widely used as an alternative to the injection route for respiratory allergy, but its pharmacokinetics in humans is poorly known, and data are available only for Par j 1 allergen. We aimed at assessing the biodistribution of iodine-123-radiolabelled Der p 2 in allergic volunteers.


METHODS
Purified Der p 2 and its monomeric allergoid were radiolabelled with iodine-123 and administered sublingually to 7 allergic volunteers. The subjects were allowed to swallow 6 min after administration. Dynamic (up to 10 min) and static scintigraphic images (30 min, 1, 2, 3 and 20 h) were recorded, and blood samples were obtained at different time points to measure the plasma radioactivity and to assess the presence of circulating radiolabelled species by gel chromatography.


RESULTS
The local pharmacokinetics did not differ between allergen and allergoid. Plasma radioactivity began to increase only after swallowing and peaked at 1-2 h. Both the allergen and the allergoid persisted in the mouth for several hours, and traces could be detectable up to 20 h. At radioactivity plasma peak, gel chromatography showed that a fraction of the allergoid, but not the allergen, was absorbed as an intact molecule.


CONCLUSIONS
These results indicate that the pharmacokinetics of sublingual administration is independent of the allergen used and characterized by the long persistence in the mouth. The contribution of enteric absorption of the allergoid in the mechanism of action of sublingual immunotherapy remains to be defined.
Bagnasco
Marcello
M
Medical and Radiometabolic Therapy, University of Genoa, Genoa, Italy.
Altrinetti
Vania
V
Pesce
Giampaola
G
Caputo
Mauro
M
Mistrello
Gianni
G
Falagiani
Paolo
P
Canonica
Giorgio Walter
GW
Passalacqua
Giovanni
G
D000286:Administration, Sublingual; D000328:Adult; D000485:Allergens / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D039741:Antigens, Dermatophagoides / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D060829:Arthropod Proteins; D006801:Humans; D006967:Hypersensitivity / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D011877:Radionuclide Imaging; D014018:Tissue Distribution
D000485:Allergens; D039741:Antigens, Dermatophagoides; D060829:Arthropod Proteins; C451163:Dermatophagoides pteronyssinus antigen p 2; D007457:Iodine Radioisotopes