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Replacement of the carboxylic acid group of prostaglandin (PG) F 2␣ with a nonacidic moiety, such as hydroxyl, methoxy, or amido, results in compounds with unique pharmacology. Bimatoprost (AGN 192024) is also a pharmacologically novel PGF 2␣ analog, where the carboxylic acid is replaced by a neutral ethylamide substituent. Bimatoprost potently contracted the feline lung parenchymal preparation (EC 50 value of 35-55 nM) but exhibited no meaningful activity in a variety of PG-sensitive tissue and cell preparations. Its activity seemed unrelated to FP receptor stimulation according to the following evidence. 1) Bimatoprost exhibited no meaningful activity in tissues and cells containing functional FP receptors. 2) Bimatoprost activity in the cat lung parenchyma is not species-specific because its potent activity in this preparation could not be reproduced in cells stably expressing the feline FP receptor. 3) Radioligand binding studies using feline and human recombinant FP receptors exhibited minimal competition versus [3 H]17-phenyl PGF 2a for Bimatoprost. 4) Bimatoprost pretreatment did not attenuate PGF 2␣ -induced Ca 2ϩ signals in Swiss 3T3 cells. 5) Regional differences were apparent for Bimatoprost but not FP agonist effects in the cat lung. Bimatoprost reduced intraocular pressure in ocular normotensive and hypertensive monkeys over a 0.001 to 0.1% dose range. A single-dose and multiple-dose ocular distribution/metabolism studies using [ 3 H]Bimatoprost (0.1%) were performed. Within the globe, bimatoprost concentrations were 10-to 100-fold higher in anterior segment tissues compared with the aqueous humor. Bimatoprost was overwhelmingly the predominant molecular species identified at all time points in ocular tissues, indicating that the intact molecule reduces intraocular pressure.Eicosanoids and related fatty acids have long been the subject of extensive investigation. More recently, it has become apparent that the corresponding neutral lipids exist for several fatty acids (Devane et al

ABSTRACT:The objectives of the study were to evaluate the distribution of brimonidine (␣ 2 -adrenergic agonist) into anterior and posterior ocular tissues. Single or multiple doses of a 0.2 or 0.5% brimonidine tartrate solution were administered to one or both eyes of monkeys or to one eye of rabbits. Brimonidine was administered intraperitoneally to rats. After topical administration, [14 C]brimonidine was rapidly absorbed into the cornea and conjunctiva and distributed throughout the eye. [ 14 C]Radioactivity was higher and cleared more slowly in pigmented tissues (iris/ciliary body, choroid/retina, and optic nerve) than in nonpigmented tissues. Single and multiple dosing led to a similar drug distribution, with higher levels of brimonidine measured in pigmented tissues after multiple dosing. Most of the radioactivity extracted from ocular tissues represented unchanged brimonidine. In the rabbits and the monkey treated in only one eye, levels of radioactivity in the untreated eye were low, consistent with the low systemic levels and rapid drug clearance. Posterior ocular tissue concentrations of radioactivity exceeded systemic blood concentrations. The vitreous humor brimonidine concentrations in monkeys treated topically with 0.2% brimonidine tartrate was 82 ؎ 45 nM. Vitreous levels in rabbits confirmed the penetration of brimonidine to the posterior segment. Similar concentrations of brimonidine (22 to 390 nM) were measured in the vitreous and retina of rats injected intraperitoneally with brimonidine. Both topically applied and systemically administered brimonidine reach the back of the eye at nanomolar concentrations sufficient to activate ␣ 2 -adrenergic receptors. The brimonidine levels achieved at the retina are relevant for neuroprotection models.Brimonidine (AGN 190342 1 ; Fig. 1) is a highly selective ␣ 2 -adrenergic agonist approved for the treatment of open-angle glaucoma. Glaucoma represents a family of ocular diseases characterized by a progressive optic neuropathy and loss of retinal ganglion nerve cells (Adkins and Balfour, 1998). One of the primary risk factors for glaucoma is elevated intraocular pressure. When applied to the eye, brimonidine activates ␣ 2 -adrenergic receptors, resulting in decreased aqueous humor production and increased uveoscleral outflow (Toris et al., 1995). These effects on aqueous humor dynamics lead to a reduction in intraocular pressure.Laboratory studies with brimonidine suggest that activation of ␣ 2 -receptors in the retina and/or optic nerve can promote the survival of retinal ganglion nerve cells (David, 1998). Studies show that intraperitoneal and topical administration of brimonidine promoted retinal ganglion cell survival after calibrated optic nerve compression and ischemia/reperfusion in animal models of neuronal injury Yoles et al., 1999;Donello et al., 2001). Importantly, if the ocular instillation of brimonidine promotes retinal ganglion cell survival in glaucomatous neuropathy, then a new therapeutic approach to glaucoma management may be indicated in ...

We investigated the formation of PGF 2 ␣ 1-ethanolamide, PGE 2 1-ethanolamide, and PGD 2 1-ethanolamide (prostamides F 2 ␣ , E 2 , and D 2 , respectively) in liver, lung, kidney, and small intestine after a single intravenous bolus administration of 50 mg/kg of anandamide to normal and fatty acid amide hydrolase knockout (FAAH ؊ / ؊ ) male mice. One group of three normal mice was not dosed (naïve) while another group of three normal mice received a bolus intravenous injection of 50 mg/kg of anandamide. Three FAAH ؊ / ؊ mice also received an intravenous injection of 50 mg/kg of anandamide. After 30 min, the lung, liver, kidney, and small intestine were harvested and processed by liquid-liquid extraction. The concentrations of prostamide F 2 ␣ , prostamide E 2 , prostamide D 2 , and anandamide were determined by HPLC-tandem mass spectrometry. Prostamide F 2 ␣ was detected in tissues in FAAH ؊ / ؊ mice after administration of anandamide. Concentrations of anandamide, prostamide E 2 , and prostamide D 2 in liver, kidney, lung, and small intestine were much higher in the anandamide-treated FAAH ؊ / ؊ mice than those of the anandamide-treated control mice.This report demonstrates that prostamides, including prostamide F 2 ␣ , were formed in vivo from anandamide, potentially by the cyclooxygenase-2 pathway when the competing FAAH pathway is lacking.

This study compared the precision and accuracy of 4 tear sampling methods. In vivo, albino rabbits were treated with single bilateral eye drops ofofloxacin 0.3% solution, 3 hr after which tear samples were collected using capillary tubes (CT), surgical sponges (SS), or tear strips for 15 sec (15sTS) or 60 sec (60sTS). In vitro, CT, SS, and tear strips were spiked with known volumes of ofloxacin solution in order to assess the bioanalytical accuracy of each technique. Ofloxacin levels were quantified by HPLC in all samples. Results showed that tear volumes and ofloxacin masses sampled in vivo depended on sampling method. Tear volume followed the rank order 60sTS > 15sTS > SS > CT. The volume collected by 60sTS exceeded precorneal tear volume. Ofloxacin mass followed the order 60sTS approximately 15sTS > SS > CT. Tear concentrations (mean +/- SD; N = 12) were 3.28 +/- 3.76 microg/g for 60sTS, 10.3 +/- 10.0 microg/g for 15sTS, 9.75 +/- 8.04 microg/g for SS, and 5.83 +/- 3.35 microg/g for CT. In vitro, SS, 15sTS, and 60sTS yielded accuracies of 103-107% and coefficients of variation (CV) < 9%. CT was only 85% accurate with a CV of 31%, indicating incomplete extraction during analysis. We concluded from this study that: 1) rabbit tear sampling by SS was rapid, easy, accurate, precise, and easily analyzable; 2) sampling by CT or 15sTS was accurate, but may require aggressive extraction (for CT) or be affected by tear flow rate (for 15sTS); and 3) tear sampling by 60sTS underestimated actual tear concentrations.