Pharmacokinetics of an allergen and a monomeric allergoid for oromucosal immunotherapy in allergic volunteers

Background and objective Little is known about the pharmacokinetics of alle rgens for local immunotherapy. Thus, we studied the pharmacokinetics in all ergic volunteers of a commercial allergenic vaccine in orosoluble tablets ( LAIS(R), Lofarma S.p.A). Methods The carbamylated monomeric allergoid derived from Parietaria judaic a major allergen (Par j 1), characterized by maintenance of the original mo lecular size, and the native allergen, were radiolabelled with I-123, then incorporated into the commercial soluble tablets and administered to allerg ic subjects. Early sequential and late static scintigraphic acquisitions we re performed, and plasma radioactivity was measured at different time inter vals. Results No difference in local pharmacokinetics was observed between the al lergen and the allergoid: part of the tracer was retained in the mouth for at least 2 h after swallowing. No direct absorption through the oral mucosa could be detected, as plasma radioactivity increased only after swallowing and peaked at 2 h. However, the plasma peak attained with the allergoid in tablets was significantly higher with respect to the native allergen. Fina lly, some undegraded allergoid, but not the allergen, could be constantly d etected in the bloodstream at plasma peak. Conclusions The results showed a similar behaviour of the allergoid and the allergen in tablets as far as their local kinetics are concerned, whereas plasma peak was higher with the allergoid than with the allergen. Therefore we conclude that the chemical modification of the allergen may affect its pharmacokinetics, by making it less susceptible to enzymatic degradation.