A comparative study of latanoprost (Xalatan) and isopropyl unoprostone (Rescula) in normal and glaucomatous monkey eyes

Analysis of the Responsiveness of Latanoprost, Travoprost, Bimatoprost, and Tafluprost in the Treatment of OAG/OHT Patients

Aim

Within the clinical setting, some patients have been identified as lacking in response to PGAs. This meta-analysis study aimed to evaluate the responsiveness of latanoprost, travoprost, bimatoprost, and tafluprost in OAG/OHT patients, latanoprost nonresponders (LNRs), and the IOP-reducing efficacy and safety.

Methods

A literature search was conducted on PubMed, Embase, and the Cochrane Controlled Trials Register. The primary clinical endpoint was the number of responders at the end of the study. The secondary clinical endpoint was the IOP reduction at the endpoint from baseline. Safety evaluation included five common adverse events: conjunctival hyperemia, hypertrichosis, ocular burning, ocular itching, and foreign-body sensation.

Results

Eleven articles containing ten RCTs were included in this meta-analysis study. The results highlighted that, in the OAG/OHT population, there was no statistically significant difference in the responsiveness of the four PGAs. Bimatoprost had a better IOP-reducing efficacy than latanoprost. There was no significant difference in the IOP-reducing efficacy of travoprost, latanoprost, and tafluprost. In LNRs, the responsiveness of bimatoprost, travoprost, and latanoprost did not show statistical differences. Bimatoprost reduced IOP with a greater extent than latanoprost and travoprost in LNRs, while there was no significant difference in the IOP-reducing efficacy of travoprost and latanoprost. No serious adverse events occurred with the treatment of the four PGAs. The prevalence of conjunctival hyperemia due to bimatoprost or tafluprost was significantly higher than that of latanoprost. Other adverse events had no significant difference between the four drugs.

Conclusion

The existing studies cannot prove that latanoprost, travoprost, bimatoprost, and tafluprost have different responsiveness in OAG/OHT patients. Switching to bimatoprost or travoprost cannot achieve a significant improvement in responsiveness in LNRs. Bimatoprost has a better IOP-reducing efficacy than latanoprost and travoprost. No serious adverse events occurred during treatment with any medication we studied.

Pharmacokinetics, Safety, and Intraocular Pressure-Lowering Profile of Omidenepag Isopropyl, a Selective, Nonprostaglandin, Prostanoid EP2 Receptor Agonist, in Healthy Japanese and Caucasian Volunteers (Phase I Study)

Purpose: Omidenepag isopropyl (OMDI) is a prodrug of OMD, a selective, nonprostaglandin, prostanoid EP2 receptor agonist. This phase I study aimed to investigate the pharmacokinetic properties, safety, and intraocular pressure (IOP)-lowering efficacy of OMDI.

Methods: Fourteen healthy male volunteers (7 Japanese and 7 Caucasian) 20–35 years of age received 1 drop of OMDI 0.0025% at 9:00 h in both eyes for 7 days. Blood samples were taken predose and up to 8 h postdose on days 1, 3, and 7. The plasma concentration of OMD was determined using high-performance liquid chromatography–tandem mass spectrometry. Pharmacokinetic parameters measured included the maximum plasma concentration (C_max) and the half-life (t_½) of OMD. IOP, adverse events (AEs), ophthalmic examinations, vital signs, and laboratory values were assessed.

Results:C_max for all subjects was reached after 10–15 min and decreased with a t_½ of ∼30 min. Ad hoc statistical analyses found significant differences in some pharmacokinetic parameters between Japanese and Caucasian subjects, likely due to differences in body weight. These differences reduced over 7 days of dosing and were not thought to be clinically meaningful. There was no OMD accumulation after 7 days of repeated dosing. Mean IOP was reduced by ∼4–5 mmHg between baseline and 2 h postdose, remaining stable from day 3 onward. All AEs were mild and considered treatment related.

Conclusions: Pharmacokinetic parameters of OMD were similar between Japanese and Caucasian subjects. There was no accumulation of OMD after 7 days of dosing. OMDI was well tolerated and demonstrated clinically significant IOP reductions.

Latanoprost-Eluting Contact Lenses in Glaucomatous Monkeys

PURPOSE

To assess the ability of latanoprost-eluting contact lenses to lower the intraocular pressure (IOP) of glaucomatous eyes of cynomolgus monkeys.

DESIGN

Preclinical efficacy study of 3 treatment arms in a crossover design.

PARTICIPANTS

Female cynomolgus monkeys with glaucoma induced in 1 eye by repeated argon laser trabeculoplasty.

METHODS

Latanoprost-eluting low-dose contact lenses (CLLO) and high-dose contact lenses (CLHI) were produced by encapsulating a thin latanoprost-polymer film within the periphery of a methafilcon hydrogel, which was lathed into a contact lens. We assessed the IOP-lowering effect of CLLO, CLHI, or daily latanoprost ophthalmic solution in the same monkeys. Each monkey consecutively received 1 week of continuous-wear CLLO, 3 weeks without treatment, 5 days of latanoprost drops, 3 weeks without treatment, and 1 week of continuous-wear CLHI. On 2 consecutive days before initiation of each study arm, the IOP was measured hourly over 7 consecutive hours to establish the baseline IOP. Two-tailed Student t tests and repeated-measures analysis of variance were used for statistical analysis.

MAIN OUTCOME MEASURES

Intraocular pressure.

RESULTS

Latanoprost ophthalmic solution resulted in IOP reduction of 5.4±1.0 mmHg on day 3 and peak IOP reduction of 6.6±1.3 mmHg on day 5. The CLLO reduced IOP by 6.3±1.0, 6.7±0.3, and 6.7±0.3 mmHg on days 3, 5, and 8, respectively. The CLHI lowered IOP by 10.5±1.4, 11.1±4.0, and 10.0±2.5 mmHg on days 3, 5, and 8, respectively. For the CLLO and CLHI, the IOP was statistically significantly reduced compared with the untreated baseline at most time points measured. The CLHI demonstrated greater IOP reduction than latanoprost ophthalmic solution on day 3 (P = 0.001) and day 5 (P = 0.015), and at several time points on day 8 (P < 0.05).

CONCLUSIONS

Sustained delivery of latanoprost by contact lenses is at least as effective as delivery with daily latanoprost ophthalmic solution. More research is needed to determine the optimal continuous-release dose that would be well tolerated and maximally effective. Contact lens drug delivery may become an option for the treatment of glaucoma and a platform for ocular drug delivery.

Current status of unoprostone for the management of glaucoma and the future of its use in the treatment of retinal disease

INTRODUCTION

Optic nerve and retinal diseases such as glaucoma, age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are significant public health concerns and have a momentous impact on patients' functional status and quality of life. These diseases are among the most common causes of visual impairment worldwide and account for billions of dollars in healthcare expenditures and lost productivity. The importance of adequate treatment of these conditions and the need for efficacious therapeutic drugs cannot be overstated. Unoprostone continues to be developed as a potential treatment for these debilitating diseases.

AREAS COVERED

This review provides background information on unoprostone isopropyl (unoprostone), a prostanoid and synthetic docosanoid approved for the treatment of open-angle glaucoma and ocular hypertension, and recapitulates safety and efficacy data as it relates to this indication. Additionally, this review describes potential new uses of unoprostone as therapy for dry AMD and RP. A literature search of peer-reviewed publications was performed utilizing PubMed. Searches were last updated on 10 September 2012.

EXPERT OPINION

Current data indicate that unoprostone does significantly lower intraocular pressure (IOP) and has a favorable safety and tolerability profile. However, the IOP-lowering effects of unoprostone do not compare with other commercially available prostanoids and it has the disadvantage of a twice-daily rather than once-daily dosing regimen. Nonetheless, recent data suggest that unoprostone may improve neuronal survival and increase ocular blood flow, indicating that it may have some value as a therapy for glaucoma, RP and dry AMD. Further studies are needed to confirm whether unoprostone provides any clinically significant advantage over the other commercially available prostanoids.

Successfully improving ocular drug delivery using the cationic nanoemulsion, novasorb

Topical ophthalmic delivery of active ingredients can be achieved using cationic nanoemulsions. In the last decade, Novagali Pharma has successfully developed and marketed Novasorb, an advanced pharmaceutical technology for the treatment of ophthalmic diseases. This paper describes the main steps in the development of cationic nanoemulsions from formulation to evaluation in clinical trials. A major challenge of the formulation work was the selection of a cationic agent with an acceptable safety profile that would ensure a sufficient ocular surface retention time. Then, toxicity and pharmacokinetic studies were performed showing that the cationic emulsions were safe and well tolerated. Even in the absence of an active ingredient, cationic emulsions were observed in preclinical studies to have an inherent benefit on the ocular surface. Moreover, clinical trials demonstrated the efficacy and safety of cationic emulsions loaded with cyclosporine A in patients with dry eye disease. Ongoing studies evaluating latanoprost emulsion in patients with ocular surface disease and glaucoma suggest that the beneficial effects on reducing ocular surface damage may also extend to this patient population. The culmination of these efforts has been the marketing of Cationorm, a preservative-free cationic emulsion indicated for the symptomatic treatment of dry eye.

Effect of SPP 635, a renin inhibitor, on intraocular pressure in glaucomatous monkey eyes

The effect of topical application of SPP 635, a renin inhibitor, on intraocular pressure (IOP) was evaluated in the eyes of monkeys with laser induced unilateral glaucoma. A multiple-dose study was performed in 8 glaucomatous monkey eyes with 3 concentrations of SPP 635, 0.2%, 0.3% and 0.4%. IOP was measured hourly for 6 h on each day of the study beginning at 9:30 a.m. Following one baseline day (untreated) and one vehicle-treated day (50 μl drop of vehicle to the glaucomatous eye at 9:30 a.m.), a 50 μl drop (25 μl × 2) of SPP 635, 0.2%, 0.3% or 0.4%, was topically applied to the glaucomatous eye at 9:30 a.m. and 3:30 p.m. for 5 consecutive days. Twice daily administration of each of the 3 concentrations of SPP 635 for 5 days significantly (p < 0.05) reduced IOP. The maximum reduction in IOP occurred 3 or 4 h after morning dosing and was 4.3 ± 0.8 (mean ± SEM) mmHg (14%) for 0.2% SPP 635, 5.3 ± 1.0 mmHg, (19%) for 0.3% SPP 635, and 8.0 ± 1.3 mmHg (25%) for 0.4% SPP 635. The longest duration of IOP reduction was for 6 h with 0.2% or 0.3% SPP 635, and was for at least 18 h with 0.4% concentration. Compared to 0.2% or 0.3% concentrations, 0.4% SPP 635 produced a greater (p < 0.05) and longer duration of IOP reduction (18 vs. 6 h). Mild conjunctival discharge appeared in 2 of 8 eyes, and hyperemia appeared in 2 eyes with the 0.3% and 0.4% concentrations on treatment days 3 and 5. Topically applied SPP 635, a new renin inhibitor, reduces IOP in glaucomatous monkeys in a dose-dependent manner. Renin inhibitors, are a novel class of compounds which may have potential for the treatment of glaucoma.

Evaluation of rebound tonometry in non-human primates

To determine the accuracy and reproducibility of intraocular pressure (IOP) measurements obtained with the TonoVet® rebound tonometer in cynomolgus macaques and to determine the effects of corneal thickness on measurements obtained by the TonoVet®. The anterior chambers of both eyes of anesthetized monkeys were cannulated with branched 23-G needles; one branch was connected to a vertically adjustable reservoir and the other to a pressure transducer. IOP was increased by 5 mmHg increments and then decreased by 10 mmHg decrements. IOP was measured using the TonoVet® at each increment and decrement by 2 independent observers and at every other increment and every decrement by a single observer using 'minified' Goldmann applanation tonometry. Central corneal thickness was measured with a PachPen(TM) ultrasonic pachymeter. TonoVet® readings correlated well with manometric IOP (slope = 0.972, r(2) coefficient = 0.955). No significant differences were observed when comparing eyes or operators; however there was a non-significant trend for TonoVet® readings taken in right eyes to be closer to manometric IOP than those taken in left eyes. The TonoVet® had a non-significant tendency to underestimate manometric IOP. TonoVet® readings obtained during the decremental phase of the experiment were significantly closer (p < 0.004) to manometric IOP than those obtained during the incremental phase. Central corneal thickness significantly increased (p < 0.0001) over the course of the experiment. The TonoVet® rebound tonometer is a reliable and accurate tool for the measurement of IOP in cynomolgus macaques. This tonometer has several advantages, including portability, ease of use, and brief contact with the corneal surface making topical anesthetics unnecessary.

Unoprostone isopropyl rescues retinal progenitor cells from apoptosisin vitro

PURPOSE

Unoprostone isopropyl is an ocular hypotensive that was originally produced as a prostaglandin F2alpha analogue and is eventually recognized as a synthetic docosanoid. The compound is recently suggested to have potent neuroprotective ability in the retina. The purpose of this study is to test whether and how the biologically active metabolites of unoprostone isopropyl rescue retinal neuro-glial progenitor cells from apoptosis.

METHODS

R28 cells were deprived of serum for 24 hr with or without varying concentrations of unoprostone metabolite M1 or M2 or vehicle in the presence or absence of specific inhibitors against several types of signal transduction proteins. Immunocytochemistry against activated caspase-3 with Hoechst nuclear staining was performed.

RESULTS

Up to 15%of R28 cells became pyknotic and activated caspase-3 immunoreactive after 24-hr serum withdrawal. M1, but not M2, significantly reduced apoptotic cells in a dose-dependent fashion with a maximal effect at 100 microM (p < .0001). LY294002, the phosphatidylinositol 3-OH kinase (PI3K) inhibitor, and KT5823, the protein kinase G (PKG) inhibitor, reversed the antiapoptotic effect of M1.

CONCLUSIONS

The unoprostone metabolite M1 protects retinal neuro-glial progenitor R28 cells from apoptosis induced by serum deprivation via the PI3K and PKG pathways.

Vasodilatory mechanism of unoprostone isopropyl on isolated rabbit ciliary artery

PURPOSE

To clarify the vasodilatory mechanism of unoprostone isopropyl (unoprostone), a PG F2alpha related compound used for treatment of glaucoma, we have investigated the effect of this drug and its metabolites on isolated rabbit ciliary artery in vitro.

METHODS

Under the dissecting microscope, ciliary arteries were prepared from albino rabbit eyes and mounted in a myograph system. The effects of unoprostone isopropyl and other agents were investigated using isometric tension recording methods.

RESULTS

Unoprostone induced a dose-dependent relaxation in ciliary arteries that were pre-contracted with high-K solution, 10 microM histamine or 10 microM PG F2alpha. Neither unoprostone metabolite M1 or M2 had a relaxant effect on the precontracted vessels. Relaxation was unaffected by inhibition of adenylyl cyclase with SQ 22536, guanylyl cyclase with ODQ, or maxi-K channels with iberiotoxin. Pretreatment with unoprostone did not affect histamine-induced transient contractions in Ca2+ -free solution. However, SKF96365, a general Ca2+ channel blocker, evoked relaxation similar to unoprostone with respect to amplitude and rate of onset.

CONCLUSIONS

Unoprostone, but not its metabolites M1 and M2, relaxed pre-contracted rabbit ciliary artery. The mechanism of vascular smooth muscle relaxation by unoprostone differs from that of IOP reduction and does not depend on adenylyl cyclase, guanylyl cyclase, or maxi-K channels. Relaxation may be mediated by inhibition of Ca2+ entry, possibly through capacitative Ca2+ channels.

Retrobulbar haemodynamic effects of the latanoprost/timolol and the dorzolamide/timolol fixed combinations in newly diagnosed glaucoma patients

The objective of this study was to compare the effect of the latanoprost/timolol fixed combination (LTFC) and the dorzolamide/timolol fixed combination (DTFC) on the retrobulbar haemodynamic and intraocular pressure (IOP) in patents with open-angle glaucoma (OAG). This was a prospective, examiner masked, randomised and crossover study. Participants were 32 consecutive subjects, who met the inclusion/exclusion criteria, with newly diagnosed OAG. Patients were randomised to either LTFC or DTFC for the first 1-month treatment phase after a 1-month washout period, without medical treatment, patients began with the opposite treatment for the second 1-month treatment period. Colour Doppler parameters in ophthalmic artery (OA) and posterior ciliary arteries (PCA), ocular perfusion pressure, IOP and systemic haemodynamics were assessed at each baseline and at the end of each treatment period. The main outcomes include peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistance index (RI) in OA and PCA. DTFC significantly increased EDV in OA from 7.55 (1.16) to 9.32 (1.22), p<0.0001, and in the PCA from 4.41 (0.70) to 5.36 (0.60), p<0.0001, and significantly decreased RI in OA from 0.775 (0.036) to 0.725 (0.032), p<0.0001, and in the PCA from 0.694 (0.045) to 0.634 (0.034). LTFC significantly decreased the EDV and significantly increased RI in PCA, p=0.0076 and p=0.0009, respectively. There were no statistical significant differences in the IOP lowering effect between both treatments. DTFC seems to have a beneficial vascular effect on retrobulbar vessels in OAG patients.

Melatonin in the eye: implications for glaucoma

Melatonin synthesis occurs in the retina of most animals as well as in humans. Circadian oscillators that control retinal melatonin synthesis have been identified in the eyes of different animal species. The presence of melatonin receptors is demonstrable by immunocytochemical studies of ocular tissues. These receptors may have different functional roles in different parts of the eye. In view that melatonin is a potent antioxidant molecule, it can be effective in scavenging free radicals that are generated in ocular tissues. By this mechanism melatonin could protect the ocular tissues against disorders like glaucoma, age-related macular degeneration, retinopathy of prematurity, photo-keratitis and cataracts. Although an increased intraocular pressure is an important risk factor in glaucoma, other concomitant phenomena like increased glutamate levels, altered nitric oxide metabolism and increased free radical generation seem to play a significant role in its pathogenesis. Data are discussed indicating that melatonin, being an efficient antioxidant with antinitridergic properties, has a promising role in the treatment and management of glaucoma.

Effects of latanoprost on rodent intraocular pressure

The aim of the present study was to evaluate the effects of the prostaglandin F2 alpha analog, latanoprost, on the intraocular pressure (IOP) in rodent eyes. Rodents have been increasingly used in glaucoma research; however, conflicting results regarding the actions of prostaglandins on rodent IOP have been published. In Wistar rats, a single dose of latanoprost (60 ng) produced a biphasic change in IOP: an initial rise in pressure (2.1+/-0.7 mmHg) peaking at 2 h, followed by a prolonged hypotension with a peak reduction in IOP (5.2+/-0.7 mmHg) at 5 h. Both the hyper and hypotensive actions of latanoprost were dose-related with ED50 values of 108 and 5.2 ng, respectively. These responses were antagonized by pretreatment with 4% pilocarpine. In Brown Norway rats and C57BL/6 mice, a single dose of latanoprost also produced a biphasic response in IOP with an initial rise in pressure peaking between 1 and 2 h, followed by prolonged hypotension from 4 to 8 h. These results demonstrate that in rodents the IOP response to topical latanoprost is characterized by an initial hypertension followed by a prolonged hypotension. This prolonged hypotension is similar to that measured in monkeys and humans. Taken together, these results support the idea that rodents can serve as in vivo models to study the actions of ocular hypotensive agents, such as prostaglandins.

Additional reduction in intraocular pressure achieved with latanoprost in normal-tension glaucoma patients previously treated with unoprostone

PURPOSE

To determine whether treatment with latanoprost eye drops is able to further reduce intraocular pressure (IOP) in normal-tension glaucoma (NTG) patients whose IOP has been well controlled with unoprostone.

PATIENTS AND METHODS

A total of 34 eyes (34 individuals) with NTG that had been treated with 0.12% unoprostone eye drops twice daily for >or=3 months were switched to treatment once daily with eye drops containing 0.005% latanoprost. IOP was measured before and 1, 2, and 3 months after the switch to latanoprost.

RESULTS

The mean IOP of all eyes was decreased significantly by 1.8, 2.9, and 2.3 mmHg at 1, 2, and 3 months after the switch from unoprostone to latanoprost treatment. The IOP of patients with an initial IOP of <or=12 or >12 mmHg was reduced by 11.0 or 19.9%, respectively, after 3 months on latanoprost. The IOP of 30 (88.2%) of the 34 eyes was further reduced by the switch from unoprostone to latanoprost.

CONCLUSIONS

Latanoprost reduced the IOP of NTG patients who had already been treated with unoprostone, even though both drugs are prostaglandin-related. Switching to latanoprost might thus achieve a maximal decrease in IOP and thereby better prevent damage to the optic nerve and loss of visual field in NTG patients.

Topical Drug Therapy in Glaucoma

Glaucoma is defined as a progressive optic neuropathy involving characteristic structural changes in the optic nerve head and corresponding visual field defects. Elevated intraocular pressure (IOP) is a major risk and causative factor for glaucomatous optic neuropathy. Although mechanisms other than elevated IOP may contribute to the underlying pathophysiology of glaucoma, reducing IOP remains the primary goal of therapy. Recent clinical studies have shown that decreasing the IOP can delay, or in some cases prevent progression of this chronic ocular disease. Over the past decade, several new medical therapies have become available for the treatment of glaucoma. In this article a review of topical glaucoma therapy is presented.

Effects of a Prostaglandin DP Receptor Agonist, AL-6598, on Aqueous Humor Dynamics in a Nonhuman Primate Model of Glaucoma

This study examines, in 11 cynomolgus monkeys with unilateral laser-induced glaucoma, the ocular hypotensive mechanism of action of AL-6598, partial agonist at the DP and EP prostanoid receptors. In a crossover fashion, both eyes of each monkey were dosed twice daily with 25 microL of either AL-6598 0.01% or vehicle for 2 days and on the morning of the 3rd day. Measurements were made on day 3 of each treatment. Alternative treatments were separated by at least 2 weeks. Intraocular pressures (IOPs) were measured by pneumatonometry and aqueous flow and outflow facility by fluorophotometry. Uveoscleral outflow was calculated mathematically. In the normotensive eyes, compared to vehicle treatment, AL-6598 decreased IOP from 22.5 +/- 0.7 to 18.7 +/- 0.9 mmHg (P = 0.006), increased uveoscleral outflow from 0.47 +/- 0.17 to 1.22 +/- 0.17 microL/min (P = 0.03), and increased aqueous flow from 1.49 +/- 0.10 to 1.93 +/- 0.13 microL/min (P = 0.01). No measurement in AL-6598-treated hypertensive eyes was significantly different from vehicle treatment. It is concluded that AL-6598 reduces IOP by increasing uveoscleral outflow in normotensive eyes of ketamine-sedated monkeys, despite an increase in aqueous flow. This effect is different from that of PGD(2), which decreases aqueous flow, and of the selective DP receptor agonist, BW245C, which increases both outflow facility and uveoscleral outflow in addition to decreasing aqueous flow.

Intraocular metabolites of isopropyl unoprostone

PURPOSE

It is still unknown which metabolite of isopropyl unoprostone is responsible for reducing intraocular pressure. This study was carried out to measure intraocular metabolites of isopropyl unoprostone in the aqueous humor of primate and human eyes.

METHODS

Nine monkeys were randomly divided into three groups, all of which received isopropyl unoprostone. In group I, the drug was scheduled to be instilled at 0 hr, in group II at 1 hr, and in group III at 2 hr, prior to aqueous humor aspiration in order to determine metabolite concentration. Furthermore, 27 patients scheduled for cataract surgery and intraocular lens implantation were divided into five groups that received isopropyl unoprostone. In group A, the drug was scheduled to be instilled at 0 hr, in group B at 1 hr, in group C at 2 hr, in group D at 3 hr, and in group E at 4 hr, prior to surgery. At the beginning of the operation, the aqueous humor was aspirated. Metabolites of isopropyl unoprostone in the aqueous humor were determined by high-performance liquid chromatography.

RESULTS

M1 (3-[(1R,2R,3R,5S)-3,5-dihydroxy-2-(3-oxodecyl)cyclopentyl]propionic acid) (unoprostone free acid) and M2 ((Z)-7-[(1R,2R,3R,5S)-3,5-dihydroxy-2-(3-oxodecyl)cyclopentyl]hept-5-enoic acid), an intraocular oxidized metabolite of isopropyl unoprostone, were measured. M1:M2 in monkeys was respectively 0:0 ng/ml in group I, 150.2 +/- 45.1:9.5 +/- 1.7 (p < 0.05) in group II, and 74.6 +/- 31.4:19.2 +/- 5.3 (p < 0.01) in group III. M1:M2 in humans was respectively 0:0 ng/ml in group A, 50.6 +/- 22.3:3.2 +/- 1.3 (p < 0.05) in group B, 125.0 +/- 23.1:12.2 +/- 3.4 (p < 0.001) in group C, 144.9 +/- 33.8:24.5 +/- 6.2 (p < 0.01) in group D, and 56.7 +/- 21.5:18.7 +/- 5.3 (p < 0.05) in group E.

CONCLUSIONS

A free acid of isopropyl unoprostone is the major intraocular metabolite of isopropyl unoprostone that is expected to act on target tissues in the eyes of both monkeys and humans.

Primate glaucoma models

The monkey model of ocular hypertension (OHT) with its resultant optic neuropathy closely reflects the optic neurodegeneration associated with human glaucoma. Utilization of the experimental glaucoma model (ExpG) in non-human primates (NHP) has led to advances in the understanding of aqueous humor dynamics, glaucomatous changes in the visual pathways from photoreceptors to the visual cortex, and anterior and posterior ocular segment pharmacological effects.

Glaucoma medication and aqueous humor dynamics

PURPOSE OF REVIEW

This review evaluates current concepts regarding the effects of glaucoma medication on aqueous humor dynamics and the impact of this on intraocular pressure control and drug selection in clinical practice.

RECENT FINDINGS

Calculations based on the Friedenwald and Goldmann equations have predicted that glaucoma medications that increase pressure-sensitive aqueous outflow will dampen intraocular pressure spikes and therefore may be advantageous over drugs that do not increase outflow facility.

SUMMARY

Further experimental research is required to verify the influence of increased outflow facility on intraocular pressure fluctuation and the effect of this on glaucoma progression.

Effects of Travoprost on Aqueous Humor Dynamics in Monkeys

PURPOSE

To determine the mechanism by which travoprost, a prodrug of a prostaglandin F2alpha analog, reduces intraocular pressure (IOP) in cynomolgus monkey eyes.

METHODS

One eye each of 12 monkeys was treated with laser burns to the trabecular meshwork to elevate IOP. At least 4 months later (Baseline Day), IOP was measured by pneumatonometry (9:00 AM and 11:45 AM), and aqueous flow and outflow facility were determined by a fluorophotometric method. Uveoscleral outflow was calculated. Both eyes were treated with travoprost 0.004% at 9:00 AM and 5:00 PM for two days and at 9:30 AM on the third day (Treatment Day), when measurements were repeated as on Baseline Day. Statistical analyses were performed using two-tailed, paired t tests.

RESULTS

On Treatment Day compared with Baseline Day, IOP in hypertensive eyes was reduced at 2.25 hours (25.8 +/- 11.2 vs 33.7 +/- 13.2 mm Hg; mean +/- standard error of the mean [SEM]; P = 0.02) and 16 hours (26.3 +/- 10.2 vs 35.1 +/- 13.6 mm Hg; P = 0.02) after treatment. The increase in uveoscleral outflow was not significant. In normotensive eyes, IOP was reduced at 2.25 hours (19.0 +/- 3.7 vs 23.0 +/- 4.0 mm Hg; P = 0.03) and 16 hours (20.7 +/- 5.4 vs 23.4 +/- 5.3 mm Hg; P = 0.01) after treatment, and uveoscleral outflow was significantly (P = 0.02) increased (1.02 +/- 0.43 vs 0.35 +/- 0.72 microL/min).

CONCLUSION

Travoprost reduces IOP in normotensive monkey eyes by increasing uveoscleral outflow. The IOP reduction in hypertensive eyes is probably via the same mechanism, although the increased uveoscleral drainage did not reach statistical significance. Travoprost had no effect on aqueous flow or outflow facility.

Switching to latanoprost monotherapy for 24 weeks in glaucoma patients

PURPOSE

To investigate the intraocular pressure lowering effect in glaucoma patients switched to latanoprost therapy from isopropyl unoprostone given as monotherapy or in combination with a beta-blocker.

METHODS

Patients with primary open angle glaucoma or normal tension glaucoma treated with 0.12% isopropyl unoprostone as monotherapy or in combination with a beta-blocker were eligible for this single-center clinical study. Of the 51 patients (51 eyes) enrolled, 18 were men and 33 were women aged 62.1 +/- 12.3 years (mean +/- SD). Twenty-two patients had primary open angle glaucoma, and 29 patients had normal tension glaucoma. Intraocular pressure was measured twice within 3 months prior to the switch, and the mean value was taken as the baseline. The patients were then switched to latanoprost (0.005%) monotherapy (once-daily administration), and changes in intraocular pressure were monitored. One physician measured intraocular pressure after 4, 8, 16, and 24 weeks of administration in this 24-week study.

RESULTS

The mean intraocular pressures were 16.0 +/- 2.4 mmHg at baseline, 13.7 +/- 2.3 mmHg after 4 weeks, 13.1 +/- 2.1 mmHg after 8 weeks, 13.6 +/- 2.0 mmHg after 16 weeks, and 13.3 +/- 2.4 mmHg after 24 weeks. A significant decrease in intraocular pressure was noted at all time points in both groups (paired t-test, p < 0.0001), and the intraocular pressure lowering effect persisted through week 24 of administration (analysis of variance, p < 0.0001).

CONCLUSIONS

Switching to latanoprost monotherapy elicits further reduction in intraocular pressure in patients with primary open angle glaucoma or normal tension glaucoma.

Effect of 5-MCA-NAT, a putative melatonin MT3 receptor agonist, on intraocular pressure in glaucomatous monkey eyes

PURPOSE

5-MCA-NAT, a putative melatonin MT3 receptor agonist, reduced intraocular pressure (IOP) in ocular normotensive rabbit eyes. This study evaluates the effect of topical application of 5-MCA-NAT on IOP in monkey eyes with laser-induced unilateral glaucoma.

METHODS

A multiple-dose study was performed in 8 glaucomatous monkey eyes. One 25-microL drop of 5-MCA-NAT (2%) was applied topically to the glaucomatous eye at 9:30 am and 3:30 pm for 5 consecutive days. IOP was measured hourly for 6 hours beginning at 9:30 am for one baseline day, one vehicle-treated day, and treatment days 1, 3, and 5 with 5-MCA-NAT.

RESULTS

Compared with vehicle treatment, twice daily administration of 5-MCA-NAT for 5 days reduced (P < 0.05) IOP from 1 hour to 5 hours after the first dose, and the IOP-lowering effects were shown to last at least 18 hours following administration, based on IOP measurements made after the fourth and eighth doses. The ocular hypotensive effect of 5-MCA-NAT was enhanced with repeated dosing. The maximum reduction (P < 0.001) of IOP occurred at 3 hours after each morning dose, and was 4.0 +/- 0.5 (mean +/- SEM) mm Hg (10%) on day 1, 5.6 +/- 0.8 mm Hg (15%) on day 3, and 7.0 +/- 1.1 mm Hg (19%) on day 5. Adverse ocular or systemic side effects were not observed during the 5 days of treatment.

CONCLUSIONS

5-MCA-NAT, a putative melatonin MT3 receptor agonist, reduces IOP in glaucomatous monkey eyes. Melatonin agonists with activity on the putative MT3 receptor may have clinical potential for treating elevated IOP.

Effect of Different Dose Schedules of 0.15% Unoprostone Isopropyl on Intraocular Pressure and Pupil Size in the Glaucomatous Beagle

The changes in intraocular pressure (IOP) and pupil size (PS) after instillations of 0.15% unoprostone isopropyl (Rescula, Novartis Ophthalmics, Duluth, GA) were investigated in the spontaneous glaucoma Beagle model. From the first-day baseline IOP of 27.3+/-3.2 mmHg placebo eye and 32.8+/-5.1 mmHg control eye, the mean+/-standard error of the mean (SEM) diurnal changes after 0.15% unoprostone, at 8 AM once-daily for the next 4 days, were 15.5+/-1.3 mmHg, 14.7+/-1.9 mmHg, 16.1+/-1.1 mmHg, and 17.0+/-1.5 mmHg, respectively, and were significantly different from the control eye. After 0.15% unoprostone was instilled at 8 PM, the mean+/-SEM baseline changes from the baseline IOP (insert drug eye 9 AM) in the drug eyes were 5.9+/-2.5 mmHg, 5.2+/-4.1 mmHg, 9.7+/-2.5 mmHg, and 3.6+/-3.6 mmHg, respectively. When 0.15% unoprostone was instilled twice-daily, the mean+/-SEM baseline IOP (insert drug eye 9 AM) changes were 13.6+/-0.7 mmHg, 13.9+/-1.4 mmHg, 11.3+/-1.0 mmHg, and 9.3+/-1.4 mmHg, respectively, and were significantly different from the control eyes. Miosis occurred within 2 hours and lasted several hours. Unoprostone isopropyl instilled once-daily (AM or PM), as well as twice-daily, produces significant decreases in IOP and PS in the glaucomatous Beagle.

Studies on the mechanism of action of timolol and on the effects of suppression and redirection of aqueous flow on outflow facility

Long-term use of drugs that suppress aqueous humor formation, such as timolol and dorzolamide, or that redirect aqueous humor outflow from the trabecular meshwork, such as prostaglandin F2alpha analogues, could cause underperfusion of the trabecular meshwork and a secondary decrease in outflow facility. We investigated the mechanism of suppression of aqueous humor formation by timolol in monkey eyes by measuring aqueous humor ascorbate levels. We also determined whether suppression of aqueous humor formation with and without redirection of aqueous humor away from the trabecular meshwork could lead to a subsequent reduction in outflow facility, and whether this reduction was correlated with increased fibronectin levels in anterior chamber aqueous humor. In cynomolgus monkeys, unilateral dose/aqueous humor formation response curves were generated for timolol, dorzolamide, and a combination of timolol + dorzolamide. Aqueous humor formation and/or outflow facility were measured in both eyes after approximately four days, four weeks and seven weeks of twice daily treatment with 3.5 microg timolol + 1.0 mg dorzolamide to one eye and 30% DMSO to the other. In some monkeys, 5 microg prostaglandin F2alpha-isopropyl ester (PG) was added to timolol + dorzolamide for 4-week treatments. Intraocular pressure and corneal endothelial transfer coefficients (k(a)) were also measured at four weeks. Aqueous humor fibronectin levels were determined in four monkeys after approximately 9.5 weeks of timolol + dorzolamide treatment. Aqueous humor formation, intraocular pressure, and aqueous humor ascorbate levels were also determined in rhesus monkeys at baseline and after a single unilateral topical administration of 25 microg timolol. Compared to baseline for the same eye, aqueous humor formation was significantly decreased in treated eyes at all doses of timolol and at 1.8 and 4 mg dorzolamide. Compared to the opposite control eye, aqueous humor formation was lower in treated eyes after 3.5 and 5 microg timolol and after all doses of dorzolamide. Aqueous humor formation after treatment with 3.5 microg timolol + 1.0 mg dorzolamide was decreased in treated vs. control eyes, after four days and was suppressed in both treated and control eyes after four weeks of treatment, but not when PG was added. There was no difference in k(a) values with or without the addition of PG. Intraocular pressure was significantly lower in both treated and control eyes vs. baseline after approximately 6.5 weeks treatment with timolol + dorzolamide when taken 2 hr after the last dose and after approximately 3.5 weeks treatment with timolol + dorzolamide + PG when measured 6 hr after the last dose. Outflow facility after treatment with timolol + dorzolamide was unchanged after four days, tended to be lower in the treated vs. control eyes after four and seven weeks, and was significantly lower in treated vs. control eyes after four weeks treatment with timolol + dorzolamide + PG (0.352 +/- 0.052 vs. 0.515 +/- 0.096 microl min(-1) mmHg(-1), p < or = 0.02). Both treated vs. control eye aqueous humor fibronectin levels were below the level of detection for our assay (0.01 microg ml(-1)). The 25 microg timolol dose decreased ipsilateral, but not contralateral intraocular pressure (12.6 +/- 1.7 vs. 15.2 +/- 0.9; p < 0.05) and aqueous humor formation (1.40 +/- 0.08 vs. 2.03 +/- 0.09 microg ml(-1), p < or = 0.01). There was no difference in anterior chamber ascorbate levels in treated vs. control eyes or compared to their respective baselines. Our findings indicate that timolol affects neither ciliary epithelial transport of ascorbate nor aqueous fibronectin levels. Our data also indicate that decreasing aqueous humor formation over a period of time can lead to reduction in outflow facility, particularly when combined with therapy that redirects aqueous from the trabecular meshwork. Future intraocular pressure-lowering therapies for glaucoma may better be directed at enhancing flow through the trabecular pathway as opposed to decreasing aqueous humor formation or rerouting aqueous humor away from the trabecular meshwork.

The effects of antiglaucoma and systemic medications on ocular blood flow

Based on the body of evidence implicating ocular blood flow disturbances in the pathogenesis of glaucoma, there is great interest in the investigation of the effects of antiglaucoma drugs and systemic medications on the various ocular vascular beds. The primary aim of this article was to review the current data available on the effects of antiglaucoma drugs and systemic medications on ocular blood flow. We performed a literature search in November 2002, which consisted of a textword search in MEDLINE for the years 1968-2002. The results of this review suggest that there is a severe lack of well-designed long-term studies investigating the effects of antiglaucoma and systemic medications on ocular blood flow in glaucomatous patients. However, among the 136 articles dealing with the effect of antiglaucoma drugs on ocular blood flow, only 36 (26.5%) investigated the effects of medications on glaucoma patients. Among these 36 articles, only 3 (8.3%) were long-term studies, and only 16 (44.4%) were double-masked, randomized, prospective trials. Among the 33 articles describing the effects of systemic medications on ocular blood flow, only 11 (33.3%) investigated glaucoma patients, of which only one (9.1%) was a double-masked, randomized, prospective trial. Based on this preliminary data, we would intimate that few antiglaucoma medications have the potential to directly improve ocular blood flow. Unoprostone appears to have a reproducible antiendothelin-1 effect, betaxolol may exert a calcium-channel blocker action, apraclonidine consistently leads to anterior segment vasoconstriction, and carbonic anhydrase inhibitors seem to accelerate the retinal circulation. Longitudinal, prospective, randomized trials are needed to investigate the effects of vasoactive substances with no hypotensive effect on the progression of glaucoma.

Comparative effects of latanoprost (Xalatan) and unoprostone (Rescula) in patients with open-angle glaucoma and suspected glaucoma

PURPOSE

To compare, in paired eyes of open-angle glaucoma patients and glaucoma suspects, hydrodynamic and visual changes after 1 month of topical latanoprost in one eye and unoprostone in the other.

DESIGN

Single-center, institutional randomized clinical trial.

METHODS

After completing a washout period off all topical medication, 25 adults (mean age 54 +/- SEM 2 years) with bilateral open-angle glaucoma or glaucoma suspect status underwent morning (8 to 10 AM) and afternoon (1 to 3 PM) measurements of intraocular pressure (IOP), pulsatile ocular blood flow (POBF), contrast, sensitivity, frequency doubling technology, and Humphrey 10-2 perimetry (HVFA II) in both eyes. Each then started unoprostone 0.15% (Rescula) in one randomly assigned eye and latanoprost 0.005% (Xalatan) in the other. Unoprostone was administered at 8 AM and 8 PM and latanoprost at 8 PM with placebo at 8 AM, both from masked bottles. After 28 days, differences were determined for each measured variable by two-tailed paired t test.

RESULTS

Starting from similar baseline IOP levels, after 1 month of treatment, the mean morning IOP values differed according to the topical agent received (16.2 +/- SEM 0.6 mm Hg for latanoprost vs 17.9 +/- 0.7 mm Hg for unoprostone; P =.001). These morning pressures were 2.6 mm Hg lower than baseline in the eyes receiving latanoprost (P <.0001), and 1.6 mm Hg lower in unoprostone-treated eyes (P =.02). Afternoon values were 3.1 +/- SEM 0.6 lower than corresponding baseline in eyes receiving latanoprost, and 2.4 +/- SEM 0.6 mm Hg in unoprostone-treated eyes (P <.0001 from baseline for both medications; interdrug mean IOP difference; P =.04). Eyes receiving unoprostone showed a 1.7-db improvement in frequency doubling mean deviation (P =.03), the only significant visual function change observed. Pulsatile ocular blood flow increased 30% relative to baseline in eyes receiving latanoprost, (P <.0001) and 16% in eyes receiving unoprostone (P =.05) by the morning of day 28. That afternoon, mean POBF had increased 30% (P <.0001) relative to afternoon baseline values among eyes receiving latanoprost and 18% (P =.03) among those receiving unoprostone (interdrug change difference, P =.05). Humphrey perimetry and contrast sensitivity remained stable with both prostanoids.

CONCLUSIONS

Both latanoprost and unoprostone produced significant reductions in IOP and increases in POBF, with stable central and perimacular visual function. Latanoprost once daily produced IOP reduction and POBF increases nearly twofold greater than those obtained with unoprostone twice daily. These differences in IOP and POBF change between unoprostone and latanoprost were statistically significant.

Effects of prostaglandins on the aqueous humor outflow pathways

Topical treatments with certain prostaglandins (PGs), including FP receptor agonists, lower intraocular pressure by increasing uveoscleral outflow. Although the precise mechanism for the increased uveoscleral outflow is not known, there appears to be activation of a molecular transduction cascade and an increase in the biosynthesis of certain metalloproteinases. This leads to reduction of extracellular matrix components within the ciliary muscle, iris root, and sclera. It is possible that this reduction of extracellular matrix present within portions of the uveoscleral pathway may contribute to the mechanism of increased uveoscleral outflow. Additional mechanisms that may contribute to the PG-mediated increase of uveoscleral outflow include relaxation of the ciliary muscle, cell shape changes, cytoskeletal alteration, or compaction of the extracellular matrix within the tissues of the uveoscleral outflow pathway. Future studies should clarify the importance of these various responses that may contribute to increased uveoscleral outflow. At present, there is no compelling evidence for a substantial facility-increasing effect on the trabecular meshwork outflow for any of these compounds.

Current status of prostaglandin therapy: latanoprost and unoprostone

Latanoprost, a prostaglandin F(2alpha) analog prodrug, and unoprostone, an analog of a prostaglandin metabolite, have been shown to be effective in decreasing intraocular pressure when used alone or in combination with other ocular hypotensive agents. The increase in the uveoscleral outflow and some of the side effects are probably FP-receptor mediated, which may account for some differences between the cited drugs. This article reviews the recent literature available on the clinical efficacy of these prostanoids, as well as the studies directly comparing these drugs.

Comparison between isopropyl unoprostone and latanoprost by prostaglandin E(2)induction, affinity to prostaglandin transporter, and intraocular metabolism

The pharmacological differences between isopropyl unoprostone (referred to as unoprostone) and latanoprost, concerning their induction of endogenous prostaglandin E(2)(PGE(2)) and affinity to a human prostaglandin transporter (PGT), were investigated. Freshly dissected bovine iris tissues were incubated with major intraocular metabolites of unoprostone, M1 and M2, acid of latanoprost, or PGF(2 alpha), and PGE(2)induction was measured. Affinities of M1, M2, latanoprost, acid of latanoprost, and PGF(2 alpha)to PGT molecule were measured using PGT-cDNA transfected HeLa cells by an isotopic influx assay.(3)H-unoprostone was incubated with freshly prepared serum, aqueous humor, or frozen stored fetal bovine serum (FBS), and the radioactivity of supernatants was measured to investigate their metabolism of(3)H-unoprostone.M2, acid of latanoprost, and PGF(2 alpha)significantly increased a release of PGE(2)compared with the control. 10 microM indomethacin completely inhibited PGE(2)induction by acid of latanoprost and PGF(2 alpha), while 100 microM indomethacin was required to inhibit PGE(2)induction completely by M1 and M2. Unoprostone, M1, M2, and latanoprost showed little affinity to PGT, while acid of latanoprost had an affinity to PGT. Freshly prepared serum and aqueous humor metabolized unoprostone, but frozen stored FBS did not. The release of endogenous PGE(2)may play an important role of action by means of PG analogs, and differences in indomethacin-related inhibition of PGE(2)release and in affinities to PGT may in part cause their different actions.

Effects of latanoprost and unoprostone when used alone or in combination for open-angle glaucoma

PURPOSE

To evaluate the effects of latanoprost and unoprostone on the intraocular pressure (IOP) and on the tonographic outflow facility in glaucoma patients when used alone or in combination.

DESIGN

Open label randomized clinical study.

METHODS

Fifty-two patients (52 eyes) with primary open-angle glaucoma were randomly divided into two groups. One group initially received only latanoprost 0.005% once daily and the other group, only unoprostone 0.12% twice daily. The study period was 12 weeks: in the first 6 weeks, latanoprost or unoprostone was given as monotherapy, and in the last 6 weeks, patients received both drugs. IOP was measured every 2 weeks by one investigator masked to the medication received by patients during the study period in the same hour as on the baseline day. At Weeks 0, 6, and 12, the coefficient of aqueous outflow was measured by tonography.

RESULTS

With latanoprost monotherapy, the baseline IOP of 22.9 +/- 2.4 mm Hg (mean +/- SD) decreased to 16.9 +/- 2.1 mm Hg (P<.01). When unoprostone was added to latanoprost, the IOP remained at 16.7 +/- 2.5 mm Hg. With unoprostone monotherapy, the baseline IOP of 22.7 +/- 2.1 mm Hg decreased to 19.4 +/- 2.4 mm Hg (P<.01). When latanoprost was added to unoprostone, the IOP decreased to 16.8 +/- 1.7 mm Hg (P<.01). There was no significant change in the coefficient of aqueous outflow with monotherapy or the combined use of the drugs.

CONCLUSIONS

The combination of latanoprost and unoprostone does not result in a more potent hypotensive effect than latanoprost alone.

Effect of pilocarpine 4% in combination with latanoprost 0.005% or 8-iso prostaglandin E2 0.1% on intraocular pressure in laser-induced glaucomatous monkey eyes

PURPOSE

To compare the effect of pilocarpine, an agent that reduces uveoscleral outflow, on the ocular hypotensive efficacy of latanoprost and 8-iso prostaglandin E2 (PGE2).

METHODS

Each of the two treatment groups was composed of the same eight monkeys with unilateral laser-induced glaucoma. Intraocular pressure (IOP) was measured hourly for 6 hours beginning at 9:00 AM on the baseline day (Thursday before treatment week) and on treatment days 1, 3, and 5 (Monday, Wednesday, and Friday). On all five treatment days, one drop of pilocarpine 4% was administered at 9:00 AM and 3:00 PM and one drop of latanoprost 0.005% or 25 microL of 8-iso PGE2 0.1% was administered at 10:00 AM and 4:00 PM.

RESULTS

One hour after pilocarpine instillation on day 1, the reduction of IOP was similar (P > 0.90) in both treatment groups, 7.6 +/- 1.1 mm Hg (mean +/- standard error of the mean ) in the latanoprost group and 7.4 +/- 0.8 mm Hg in the 8-iso PGE2 group. However, the IOP effects of the two treatment groups became significantly different (P < 0.05) beginning 2 hours after dosing with latanoprost or 8-iso PGE, on day 1. A difference (P < 0.05) between the two groups persisted at all subsequent measurements. The reduction of IOP lessened with repeated dosing in the latanoprost and 8-iso PGE2 groups. Three hours after dosing with pilocarpine and two hours after dosing with the prostanoids, the IOP reduction was 8.3 +/- 0.9 mm Hg in the latanoprost group and 9.9 +/- 0.6 mm Hg in the 8-iso PGE2 group on day 1, and 2.1 +/- 1.0 mm Hg in the latanoprost group and 7.3 +/- 0.9 mm Hg in the 8-iso PGE1 group on day 5.

CONCLUSIONS

The smaller reductions in IOP with pilocarpine and latanoprost than with pilocarpine and 8-iso PGE2 show that pilocarpine blocks much more of the ocular hypotensive effect of latanoprost than of 8-iso PGE2. The results also indicate that pilocarpine and latanoprost are mutually antagonistic. Enhancement of uveoscleral outflow appears to account for most of the ocular hypotensive effect of latanoprost and for much less of the ocular hypotensive effect of 8-iso prostaglandin E2.

A randomized double-masked crossover study comparing latanoprost 0.005% with unoprostone 0.12% in patients with primary open-angle glaucoma and ocular hypertension

PURPOSE

To compare the intraocular pressure)-lowering effect and side effects of latanoprost 0.005% once daily with unoprostone 0.12% twice daily.

METHODS

Sixty patients with primary open-angle glaucoma or ocular hypertension were randomized to receive either latanoprost once daily in the evening and placebo once daily in the morning, or unoprostone twice daily in the morning and evening. The study was double masked and followed a crossover design with two treatment periods of 1 month separated by a 3-week washout period. The intraocular pressure was measured at 9 AM and 5 PM on the baseline and day 28 visits, and at 9 AM on day 2 and day 14 visits of each treatment period. The 9 AM measurement was taken 2 hours and 13 hours after the last drop of unoprostone and latanoprost, and the 5 PM measurement was at 10 and 21 hours, respectively. The mean of the measurements was calculated. Safety parameters were also recorded.

RESULTS

Fifty-six patients completed both treatment periods and had intraocular pressure data available for evaluation. After 1 month of treatment, latanoprost significantly reduced intraocular pressure (mean +/- SEM) by 6.1 +/- 0.5 mm Hg (P <.001) and unoprostone by 4.2 +/- 0.4 mm Hg (P <.001) adjusted from an overall baseline of 22.3 +/- 0.5 mm Hg and 23.2 +/- 0.4 mm Hg, respectively. The difference of 1.9 mm Hg between treatments was statistically significant in favor of latanoprost [P =.003, analysis of covariance (ANCOVA)]. Unadjusted analysis of responders using the percentage decrease in intraocular pressure showed that the proportion of responders in the latanoprost-treated group was greater than in the unoprostone-treated group. Adverse ocular symptoms and findings were mild in both treatment groups. Eye redness and ocular irritation were the most frequently reported events.

CONCLUSIONS

Latanoprost once daily was significantly more effective in reducing intraocular pressure compared with unoprostone twice daily after 1 month of treatment in patients with primary open-angle glaucoma and ocular hypertension. Both drugs were well tolerated with few ocular adverse events.

Effects of topical unoprostone and latanoprost on acute and recurrent herpetic keratitis in the rabbit

PURPOSE

To determine the effect of the topical ocular hypotensive drug, isopropyl unoprostone, a docosanoid molecule with very weak prostaglandin activity, on herpes keratitis in the rabbit eye.

METHODS

For acute disease, rabbit corneas inoculated with the corticosteroid-sensitive F(MP)E strain of herpes simplex virus type 1 were treated with various combinations of 0.12% isopropyl unoprostone, latanoprost, trifluridine, benzalkonium chloride 0.02%, dexamethasone sodium phosphate, ketorolac tromethamine, or saline solution beginning 1 day after infection. Severity of keratitis was evaluated in a masked manner. For recurrent disease, rabbit corneas infected with McKrae strain herpes simplex virus type 1 were treated with unoprostone or saline solution on postinfection days 25 to 42, and the presence or absence of lesions was recorded.

RESULTS

Eyes treated with unoprostone showed significantly less severe disease than saline-treated or latanoprost-treated eyes during acute infection. Unoprostone-treated and saline-treated eyes showed no significant difference in the frequency of recurrent lesions. Eyes treated with latanoprost and/or dexamethasone, separately or in combination, showed increased severity of acute herpes simplex virus keratitis, whereas benzalkonium chloride 0.02%--treated eyes showed no significant difference, compared with saline treatment. Trifluridine resulted in rapid healing.

CONCLUSIONS

Unoprostone did not increase the severity or recurrence rate of herpes simplex virus keratitis. Unoprostone requires twice-a-day administration, compared with once-a-day for latanoprost, and unoprostone lowers intraocular pressure less than latanoprost. Nevertheless, unoprostone's superior safety profile may make its use advantageous. Benzalkonium chloride alone did not make the keratitis worse.

The pros and cons of different prostanoids in the medical management of glaucoma

The prostaglandin analogs are new exciting drugs added to the therapeutic armamentarium for patients with glaucoma. Several studies have evaluated the ocular hypotensive properties and side effects of latanoprost in different forms of glaucoma. This drug, seems to be the most effective intraocular pressure (IOP)-reducing agent currently available, and has a low incidence of ocular and systemic side effects. Fewer data are available regarding unoprostone, but the IOP-reducing effect of this drug seems to be comparable or slightly inferior to that of timolol and it produces fewer side effects. When compared with unoprostone, latanoprost has been shown to effect a greater reduction in IOP. A major drawback to the use of prostaglandin analogues is the lack of long-term experience such as that currently available for other classes of agents.

Therapeutic potential of prostaglandin analogues in glaucoma

One of the most recent contributions to the therapeutic arsenal available for the treatment of glaucoma is the prostaglandin (PG) analogues. They represent a new class of ocular hypotensive drugs, targeting the uveoscleral outflow of ocular aqueous humour. Two drugs, latanoprost and unoprostone, are presently commercially available. In terms of intraocular pressure (IOP) reduction, latanoprost is the most powerful drug in clinical use today. The once daily dosing promotes compliance. Additional effect is achieved in combination with other hypotensive drugs, including those that increase trabecular outflow facility. The most frequent side effect is increased iris pigmentation that seems to be irreversible. A low frequency of cystoid macular oedema has been reported, predominantly in patients whose blood-retinal barrier (BRB) is compromised. Systemic side effects are rare. The experience with unoprostone is still much less than that with latanoprost. The ocular hypotensive mechanism of action of unoprostone is not well documented but an increase in uveoscleral outflow may be at least a part of its mode of action. Systemic side effects are rare and the ocular side effects seem to be mild. The ocular hypotensive effect is less than that of latanoprost and may not be suitable for monotherapy. It is widely accepted that the IOP alone is not responsible for the development of glaucomatous visual defects. It remains to be seen if this class of drugs will preserve vision in glaucoma patients better than other classes. More PG analogues are under development for potential clinical use.

Intraocular pressure-lowering efficacy of latanoprost in patients with normal-tension glaucoma or primary open-angle glaucoma

We investigated the intraocular pressure (IOP)-lowering potential of latanoprost in patients with normal-tension glaucoma (NTG) or primary open-angle glaucoma (POAG). This prospective study included 59 NTG and 20 POAG patients treated with the following four dosing regimens of latanoprost: patients on no previous medication received latanoprost as initial therapy (Group 1, n=31), patients on beta-blocker therapy received latanoprost as adjunctive therapy (Group II, n=9), patients on unoprostone monotherapy were switched to latanoprost monotherapy (Group III, n=14), and patients previously on dual therapy with isopropyl unoprostone and beta-blocker were switched to a combined treatment of latanoprost and beta-blocker (Group IV, n=25). IOP significantly decreased 8 weeks after initiation of latanoprost therapy by 19.9% in Group I, 20.5% in Group II, 16.6% in Group III, and 12.2% in Group IV. In Groups I and II, there was a significant positive correlation between the magnitude of IOP reduction induced by latanoprost and the IOP level before latanoprost therapy. The IOP level before latanoprost therapy is a contributing factor in the IOP-lowering efficacy of latanoprost. Latanoprost is more effective in lowering IOP than isopropyl unoprostone.

The effect of 0.12% unoprostone isopropyl (rescula) on intraocular pressure in normotensive dogs

Rescula (0.12% unoprostone isopropyl) is the first docosanoid compound approved for treatment of glaucoma in humans. It is commercially available in Japan, and is undergoing clinical testing elsewhere. The aim of this study was to evaluate the effect of Rescula on intraocular pressure (IOP) in normotensive dogs. After establishing a baseline diurnal IOP curve, six dogs were unilaterally treated with Rescula while the contralateral eye was treated with a placebo. Applanation tonometry was performed in both eyes, and pupil size was evaluated, 30 min after treatment, and at 1-hr intervals for the next 9 hr. Rescula caused a significant (p=0.014) and long-lasting decrease in IOP, from 20.49+/-2.02 mm Hg in control eyes to 15.49+/-0.69 mm Hg in treated eyes. These results suggest that Rescula is potentially efficacious in treatment of canine glaucoma.

Advances in glaucoma diagnosis and therapy for the next millennium: new drugs for trabecular and uveoscleral outflow

Advances in our understanding of the physiology and molecular biology of the trabecular and uveoscleral outflow pathways of the eye will lead to the development of new approaches for glaucoma therapy. Therapies of the future will target the structures and enzymes involved in maintaining cell shape and cell-cell and cell-extracellular matrix interactions. Altering the extracellular matrix in the ciliary muscle has been important in the intraocular pressure lowering effects of prostaglandins and will be developed further as an approach to enhancing outflow through the trabecular meshwork. Gene therapy may be used to enhance or suppress the endogenous targets that are ultimately responsible for the outflow enhancement triggered by these agents.

Prostaglandin analogues in the treatment of glaucoma

Prostaglandin (PG) analogues are a new class of ocular hypotensive drugs that have been developed for the treatment of open angle glaucoma. Two of these drugs, latanoprost and unoprostone, are presently commercially available. Latanoprost was introduced in 1996 in the US and Europe. Presently it enjoys the most widespread use and is the most well documented drug of this group. It reduces the intraocular pressure (IOP) by a mechanism of action different from other drugs; namely by increasing the uveoscleral outflow. The aqueous inflow is not affected. The optimal dose regimen is one drop of 50 microg/ml once daily, which reduces the IOP by approximately 30% in patients with glaucoma. A more pronounced ocular hypotensive effect is demonstrated when latanoprost is combined with other glaucoma therapies, including beta-blockers, adrenergic and cholinergic agonists or carbonic anhydrase inhibitors. Latanoprost is well tolerated. The drug reaches a plasma concentration below that needed for stimulation of the FP-receptor, which may explain its favourable systemic tolerability profile. The major ocular adverse effect is increased iris pigmentation, which is due to increased synthesis of melanin in the melanocytes of the iris stroma. It is most frequently seen in green-brown eyes and it is probably permanent. A low frequency of cystoid macular oedema has also been reported, predominantly in predisposed eyes. Unoprostone was launched in Japan in 1994, but there is little experience with this drug outside the Japanese market and the documentation is more limited. Its main mechanism of action is on outflow, but this is not yet fully elucidated. The recommended dosage regimen is 1 drop of 1.2 mg/ml twice daily. No comparative studies in humans between the 2 drugs have yet been published.