Loteprednol etabonate (LE) is a "soft" steroid belonging to a unique class of glucocorticoids. LE possesses a metabolically labile 17 beta-chloromethyl ester function which was designed in order to be hydrolyzed to an inactive carboxylic acid moiety. The ocular absorption and metabolism of a 14C-labelled LE was evaluated in New-Zealand White rabbits after administration of a 0.5% suspension in both eyes. At various time points following ocular administration, the cornea, aqueous humor, and iris-ciliary body were collected. LE and the putative inactive metabolites, PJ-90 and PJ-91, were identified in all 3 tissues. Levels of LE and its metabolites were highest in the cornea, and so was the ratio of metabolites to unchanged drug, suggesting that the primary site of deactivation of the drug is the corneal tissue. A substantial amount of metabolites were also detected in the iris-ciliary body, although to a lesser extent than in the cornea. The amount of drug and metabolites in the aqueous humor was very low. It is concluded that LE is indeed a soft steroid with good ocular permeation properties.
ATI-7505, an investigational 5-HT(4) receptor agonist, was designed to have similar activity as cisapride without the cardiac adverse effects, i.e. without QT prolongation. In addition, ATI-7505 is not metabolized by CYP450. The aim of the study was to assess the effect of ATI-7505 on gastrointestinal (GI) and colonic transit in healthy humans. A randomized, parallel-group, double-blind, placebo-controlled study evaluated effects of 9-day treatment with ATI-7505 (3, 10 or 20 mg t.i.d.) on scintigraphic GI and colonic transit in healthy volunteers (12 per group). Primary endpoints were gastric-emptying (GE) T(1/2), colonic geometric centre (GC) at 24 h and ascending colon (AC) emptying T(1/2). Daily stool diaries were kept. Analysis of covariance assessed overall treatment group differences, followed by post hoc unadjusted pairwise comparisons. There were borderline overall treatment effects (decrease) on GE T(1/2) (P = 0.154); the 20 mg t.i.d. of ATI-7505-accelerated GE vs placebo (P = 0.038). ATI-7505 increased colonic transit (GC24, P = 0.031) with fastest transit at 10 mg t.i.d. vs placebo (P = 0.065). ATI-7505 accelerated AC emptying T(1/2) (overall P = 0.075) with 10 mg dose vs placebo (P = 0.042). There was looser stool (Bristol stool form scale, overall P = 0.056) with the 10 and 20 mg t.i.d. doses. No safety issues were identified. ATI-7505 accelerates overall colonic transit and tends to accelerate GE and AC emptying and loosen stool consistency.
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