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Purpose: Difluprednate (6α,9-difluoro-11β,17,21-trihydroxy-1,4-pregnadiene-3,20-dione 21-acetate 17-butyrate, DFBA) has long been used as an anti-inflammatory dermatological agent. The main objectives of the current study were to evaluate the pharmacokinetic and pharmacodynamic features of DFBA when used as an ophthalmic agent, and to compare these features with those of other common ophthalmic agents, to determine which has the highest activity. Methods: A glucocorticoid (GC) receptor-binding test was performed to evaluate GC receptor-binding activity (GCRBA, the index of pharmacological effect). Using this information, we calculated dose-response curves, IC50 values, and Kd values to evaluate each drug's Ki value. Finally, we performed studies in live rabbits to compare the activity of 4 formulations [0.002%, 0.01%, or 0.05% DFBA, or an ophthalmic solution of 0.1% betamethasone sodium phosphate (BMP)] at 4 time points (0.5, 1, 2, 4 h). At each time point, blood and eye samples were taken so that Cmax (the maximum equivalent concentration of the active DFBA metabolite, DFB), Tmax (the time at which Cmax was measured), and the area under the concentration-time curve could be compared across the 4 formulations. Results: BMP had the highest Ki value (8.4 × 10−8 nmol/L), whereas DFB had the lowest (6.1 × 10−11 nmol/L). The GCRBA of DFBA was intermediate to these 2 values (7.8 × 10−10 nmol/L). Instillation of the DFBA ophthalmic emulsion in the eyes of rabbits led to dose-dependent increases in GCRBA, which was mostly attributable to the activity of DFB. The 0.05% DFBA ophthalmic emulsion elicited the greatest response in both aqueous humor and iris/ciliary body tissues, though there were no significant dose-dependent differences in GCRBA in plasma samples. Conclusions: The 0.05% DFBA ophthalmic emulsion appears to be an effective and safe anti-inflammatory treatment in ocular tissues. It is comparable, and possibly even superior, to the 0.1% BMP solution, and may be particularly useful in cases of severe disease where treatment with BMP solution alone is insufficient. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the ocular pharmacokinetics of a single dose of bromfenac sodium ophthalmic solution 0.1% in subjects undergoing routine cataract surgery with intraocular lens implantation. Methods: An open-label, phase II confirmatory study of 54 subjects undergoing cataract surgery with intraocular lens implantation. A single drop of bromfenac sodium ophthalmic solution 0.1% was administered at 30, 60, 90, 120, 180, or 240 min prior to the initiation of cataract surgery. Samples of aqueous humor were aspirated through a paracentesis and analyzed by using high-performance liquid chromatography. Based upon these data, predicted concentrations of bromfenac in the aqueous humor over 24 h were generated by using computer simulation and compared with the IC50 for bromfenac as a measure of anti-inflammatory efficacy. Results: Peak aqueous-humor concentrations of bromfenac occurred between 150 and 180 min following ophthalmic dosing, with a mean concentration of 78.7 ng/mL. The level of bromfenac decreased in a log-linear fashion with an elimination-rate constant of 1.4. Bromfenac remained above the IC50 value of cyclo-oxygenase-2 (COX-2) during the evaluated time points and over the 12-h dosing interval, using a computer model of extrapolated time points and assuming first-order elimination. Conclusions: Pharmacokinetic modeling, based upon samples collected over 240 min after a single dose of bromfenac sodium ophthalmic solution 0.1% suggests that aqueous-humor concentrations remain at clinically effective levels (above its IC50 value for COX-2) for over 12 h. Based upon this rationale, these results supported clinical trials that demonstrated the efficacy of twice-daily dosing of bromfenac sodium ophthalmic solution 0.1% to manage patients with postoperative ocular pain and inflammation. [ABSTRACT FROM AUTHOR]

Abstract: Improved dosing regimens have been proposed for various antimicrobial agents by application of pharmacokinetic/pharmacodynamic (PK/PD) principles. However, for topical ophthalmic use there are several limitations to changing the dosing regimen, such as drug formulation and bioavailability. In this study, we investigated the relationship between dosing interval and antibacterial efficacy in an in vitro PK model mimicking post-operative endophthalmitis. The in vitro PK model simulated the aqueous humour concentration following topical application of 0.3% gatifloxacin ophthalmic solution to rabbit eyes. A clinical isolate of Enterococcus faecalis was exposed to gatifloxacin three times repeatedly at various intervals from 0h to 8h. The area between the control growth curve and the bacterial killing and re-growth curve for 24h (ABBC) was used to evaluate efficacy. The ABBC showed bell-shaped dependence on the dosing interval with a peak at 3h. Under limited condition of total exposure amount, i.e. area under the concentration–time curve, the antimicrobial efficacy appears to be associated with the cumulative time of a 24-h period such that the concentration exceeds the minimum inhibitory concentration (T >MIC) rather than the peak concentration:MIC ratio. The length of intermission of T >MIC during repeated dosing appears to be proportional to the decrease in efficacy of gatifloxacin against E. faecalis. A longer dosing interval, as long as T >MIC is continuous, would likely be more efficient at preventing post-operative enterococcal endophthalmitis. However, further investigation is necessary to explore whether this model is applicable to a variety of pathogens and drugs. [Copyright &y& Elsevier]