ENHANCEMENT OF NASAL SALMON-CALCITONIN ABSORPTION BY LAUROYLCARNITINECHLORIDE IN RATS

Purpose. We investigated optimum formulation characteristics in the na sal absorption of salmon calcitonin (sCT) by incorporation of acylcarn itines. Methods. Nasal sCT formulations were administered to anestheti zed rats. Plasma calcium level was measured and pharmacological bioava ilability (P.bioav) was calculated. Results. Nasal sCT absorption was significantly enhanced by carnitines with acyl groups of 12 or more ca rbon atoms. Enhancement by lauroylcarnitine chloride (LCC) was observe d at its critical micelle concentration and reached a plateau at the c oncentration of 0.1%. Optimal absorption was achieved at a molar ratio of LCC to sCT of 5:1. Enhancement was not influenced by osmolarity an d maximum enhancement was obtained at pHs 3.1 and 4.0. Conclusions. Th e 12-carbon LCC was the strongest enhancer among acylcarnitines. Micel le formation played a key role in this enhancement effect.