Maintained reduction of intraocular pressure by prostaglandin F2 alpha-1-isopropyl ester applied in multiple doses in ocular hypertensive and glaucoma patients

Efficacy and Patient Tolerability of Omidenepag Isopropyl in the Treatment of Glaucoma and Ocular Hypertension

Current therapeutic approaches for glaucoma aim to reduce intraocular pressure (IOP), which is the only available and reliable strategy proven to control the risk of disease development and progression. Omidenepag isopropyl (OMDI) is a novel topical ocular hypotensive agent that was launched onto the market for the treatment of glaucoma and ocular hypertension (OHT). After topical instillation and during corneal penetration, OMDI is converted into the active metabolite omidenepag (OMD), which behaves as a non-prostaglandin, selective E-prostanoid subtype 2 (EP2) receptor agonist. The topical administration of 0.002% OMDI once-daily (QD) possesses a 20–35% IOP-lowering effect, comparable to that of prostaglandin analogs targeting F-prostanoid (FP) receptor QD, which are the current first-line for pharmaceutical reduction of IOP. However, the mechanism of action and adverse events (AEs) of OMDI are different from those of FP receptor agonists. OMDI reduces IOP by enhancing both conventional trabecular and uveoscleral outflow facilities without complications of prostaglandin-associated periorbitopathy (PAP) seen with FP receptor agonists. Moreover, OMDI was also effective and well-tolerated in non-/poor responders to latanoprost and showed a stable IOP-lowering effect for one year, and its concomitant use with timolol enhanced the IOP-lowering effect. OMDI demonstrated acceptable safety and tolerability with good adherence and can be used in almost every patient. However, OMDI has some AEs such as conjunctival hyperemia, corneal thickening, macular edema/cystoid macular edema and ocular inflammation. Moreover, OMDI is contraindicated in patients who are allergic to the product, in aphakic or pseudophakic eyes, and in combination with tafluprost eye drops. If used appropriately in the right patients, OMDI could be an effective treatment option for glaucoma and OHT as a first-line alternative to FP agonists. Here, we summarize the results of clinical studies of OMDI and discuss its efficacy and patient tolerability in glaucoma and OHT in this review.

Prostanoid receptor agonists for glaucoma treatment

Intraocular pressure reduction is the only available and evidence-based medical therapy for glaucoma. Currently, the first-line eye drops are prostaglandin analogues including latanoprost, travoprost, bimatoprost, and tafluprost. These drugs stimulate intraocular prostanoid false positive (FP) receptors and reduce intraocular pressure by increasing mainly uveoscleral aqueous outflow. For 2 decades since latanoprost was launched, no drug has been comparable in its efficacy. In 2018, a prostanoid EP2 agonist, omidenepag, was launched in Japan. Current FP agonists and EP2 agonists indicate comparable intraocular pressure reduction by stimulating prostanoid FP or EP2 receptors. However, their safety profiles are quite different because of the differences between the intracellular signaling pathways through their own receptors. Including these commercially available FP and EP2 receptor agonists, prostanoid receptors have a large potential to control intraocular pressure. In this review I will trace the history and development of FP and EP2 receptor agonists from their original function, and explain their potential as first-line drugs including elucidation of their efficacy and safety.

Advances in the discovery of novel agents for the treatment of glaucoma

INTRODUCTION

Glaucoma, a neuropathy characterized by increased intraocular pressure (IOP), is the major cause of blindness worldwide and its treatment aims at reducing IOP.

AREAS COVERED

The authors review the design of the main classes of anti-glaucoma agents. Drugs which interfere with the aqueous humor secretion (adrenergic agonists/antagonists, carbonic anhydrase inhibitors) and with its outflow, by means of both conventional and non-conventional pathways (prostaglandin (PG) analogs, rho kinase inhibitors, nitric oxide (NO) donors) as well as new agents (adenosine receptors modulators, melatonin - fatty acid amide hydrolase hybrids, tyrosine kinase activators, natriuretic peptide analogs) are considered.

EXPERT OPINION

The anti-glaucoma drug field has undergone several developments in recent years with the approval of at least three new drugs belonging to novel pharmacological classes, the rho kinase inhibitors ripasudil and netarsudil, and the PG-NO donor hybrid latanoprostene bunod. Eye drops with combinations of two different drugs are also available, allowing for effective IOP control, with once daily administration for some of them, which assures a better patient compliance and ease of administration. Overall, after more than a decade without new anti-glaucoma drugs, the last year afforded interesting new pharmacological opportunities for the management of this disease.

Prostaglandin receptor agonists as antiglaucoma agents (a patent review 2013 - 2018)

Introduction: Elevated intraocular pressure (IOP) is the most prevalent risk factor for glaucoma. Prostaglandin analogs are a first-line therapy for glaucoma due to their ability to reduce IOP, once-daily dosing, efficacy, and minimal side-effect profile. Many compounds targeting different PG receptors have been developed in the last years, some of them being in clinical use. Latanoprost, Bimatoprost, Travoprost, and Tafluprost are clinically used as antiglaucoma drugs and act as agonists of the PGF2α receptor. The inability to fully understand the mechanism of action of clinically used PGF2α analogs is thus a strong driver for additional research into the mechanism of action of ocular hypotensive drugs belonging to this class of pharmacological agents. Areas covered: This review explores the last 5 years (2013-2018), where many patents describing new compounds acting on different prostaglandin receptors, and mainly targeting EP1-4 and FP receptors, were released. Expert opinion: To date, there has been a growing awareness over recent years of the therapeutic use of novel derivatives as new antiglaucoma pharmaceutical products. Patents involved in discovering new approaches and new molecules for the treatment of glaucoma diseases encouraged the scientific community to increase the variety of drugs available for the treatment of ocular diseases.

Prostaglandins in the eye: Function, expression, and roles in glaucoma

Prostaglandins are small pro-inflammatory molecules derived from arachidonic acid that play roles in a multitude of biological processes including, but not limited to, inflammation, pain modulation, allergies, and bone formation. Prostaglandin analogues are the front-line medications for the treatment of glaucoma, a condition resulting in blindness due to the death of retinal ganglion cells. These drugs act by lowering intraocular pressure (IOP), a major risk factor for glaucoma. The currently used prostaglandin analogues (latanoprost, bimatoprost, tafluprost, and travoprost) mimic PGF2 and target one of the prostaglandin receptors (FP), though research into harnessing the other receptors using compounds like Sulprostone (EP3 receptor), or Iloprost (IP receptor) are currently ongoing. In this review, we summarize the research into each of the prostaglandin molecules (PGD2, PGE2, PGF2, PGI2, TXA2) and their respective receptors (DP, EP1, 2, 3, 4, FP, IP). We examine the modes of action of each of these receptors, their expression, their role in aqueous humour production and outflow within the eye, as well as their roles as medications for the treatment of glaucoma.

New prostaglandin analog formulation for glaucoma treatment containing cyclodextrins for improved stability, solubility and ocular tolerance

Latanoprost is a practically insoluble prostaglandin F2α analog considered a first-line agent for glaucoma treatment. From a pharmaceutical point of view, latanoprost is challenging to be formulated as an eye drop due to its poor water solubility and the presence of an ester bond that needs to be cleaved in vivo but maintained unchanged during storage. Cyclodextrins (CDs) are known to form complexes with hydrophobic drugs, influencing their stability, availability, solubility, and tolerance in a non-predictable manner. A variety of CDs including native α, β, and γCDs as well as substituted hydroxypropylβCD, hydroxypropylγCD, dimethylβCD, sulphatedβCD, and propylaminoβCD were screened and the most appropriate CD for the formulation of latanoprost for an ocular topical application was selected. Among the tested CDs, propylaminoβCD had the best trade-off between latanoprost stability and availability, which was confirmed by its complex constant value of 3129M(-1). Phase-solubility and NMR investigations demonstrated that the propylaminoβCD effectively formed a complex involving the ester group of latanoprost providing protection to its ester bond, while ensuring proper latanoprost solubilization. Furthermore, in vivo experiments demonstrated that the latanoprost-propylaminoβCD formulation led to lower ocular irritation than the commercial latanoprost formulation used as a reference. The latanoprost-propylaminoβCD formulation was demonstrated to successfully address the main stability, solubility, and tolerance limitations of topical ocular latanoprost therapy for glaucoma.

Therapeutic uses of prostaglandin F(2α) analogues in ocular disease and novel synthetic strategies

The pharmacological management of glaucoma and ocular hypertension has significantly changed over the last 18 years with the introduction of PGF2α analogues, more specifically latanoprost (6), travoprost (8), bimatoprost (10) and tafluprost (12). Prostanoids are currently the first-line medicines among ocular antihypertensive drugs in terms of efficacy, safety, patient compliance and medical economy. Their ability to effectively reduce intraocular pressure with once-per-day dosing, ocular tolerability comparable to timolol and general lack of systemic adverse effects have made them the mainstay of pharmacological therapy for glaucoma and ocular hypertension all over the world. The present review reports a novel, convergent and highly diastereoselective method for the synthesis of PGF2α analogues from the structurally advanced prostaglandin phenylsulfone (5Z)-(+)-15 and new ω-chain synthons. The biochemistry, clinical efficacy and side effects of four commercially available PGF2α analogues, currently used as first-line agents for reducing intraocular pressure in patients with glaucoma or ocular hypertension, are also discussed.

Prodrug strategies in ocular drug delivery

Poor bioavailability of topically instilled drug is the major concern in the field of ocular drug delivery. Efflux transporters, static and dynamic ocular barriers often possess rate limiting factors for ocular drug therapy. Different formulation strategies like suspension, ointment, gels, nanoparticles, implants, dendrimers and liposomes have been employed in order to improve drug permeation and retention by evading rate limiting factors at the site of absorption. Chemical modification such as prodrug targeting various nutrient transporters (amino acids, peptide and vitamin) has evolved a great deal of interest to improve ocular drug delivery. In this review, we have discussed various prodrug strategies which have been widely applied for enhancing therapeutic efficacy of ophthalmic drugs. The purpose of this review is to provide an update on the utilization of prodrug concept in ocular drug delivery. In addition, this review will highlight ongoing academic and industrial research and development in terms of ocular prodrug design and delivery.

Differential activity and clinical utility of latanoprost in glaucoma and ocular hypertension

Background

The purpose of this study was to demonstrate the hypotensive efficacy and tolerability of latanoprost when used as monotherapy and as polytherapy associated with antiglaucomatous medication proven to be ineffective in keeping intraocular pressure under control.

Methods

Three hundred and thirty-seven patients (672 eyes) affected by primary open-angle glaucoma and intraocular hypertension were recruited over a period of 10 years from the Glaucoma Centre, Department of Ophthalmological Sciences, University of Rome “Sapienza”, and treated, subject to informed consent, with latanoprost 0.005% alone or in combination with other ocular hypotensive drugs. The patients were followed during this period at regular intervals, with determination of visual field, fundus oculi, visual acuity, and eventual onset of local and systemic side effects.

Results

Latanoprost used as monotherapy and as polytherapy renders possible optimal and durable control of intraocular pressure in the form of one antiglaucomatous drug because it can substitute for one or more drugs and obtain the same hypotensive effect.

Conclusion

Latanoprost can be described as the ideal hypotensive drug, not only because of its ideal compliance profile (only one daily dose in the evening), excellent hypotensive effect, and, above all, few systemic side effects.

A review of the use of latanoprost for glaucoma since its launch

INTRODUCTION

Prostaglandins are increasingly used as first choice treatment for glaucoma because they are highly effective, lack relevant systemic side effects and require just once-daily administration. Latanoprost is an ester prodrug analog of prostaglandin F2α, which reduces intraocular pressure (IOP) by increasing uveoscleral outflow. Latanoprost 0.005% has received European and US approval as the first-line drug for reducing IOP in patients with open-angle glaucoma or ocular hypertension. Following the recent patent expiry for Xalatan®, a number of latanoprost generics have entered the glaucoma market.

AREAS COVERED

This review, achieved through PubMed and Medline research methods, describes the composition, pharmacokinetics, mode of action, efficacy, side effects and safety profile of latanoprost.

EXPERT OPINION

Latanoprost was the first prostaglandin analog introduced in glaucoma management and it dramatically changed the market of the disease thanks to its efficacy and safety. Conjunctival hyperemia, which is commonly found after latanoprost use, is associated with a minor efficacy and duration of trabeculectomy; yet, from the ophthalmologist's perspective, this side effect seems largely counterbalanced by the high efficacy and safety of this compound. It is always advisable to consider the pro-inflammatory mode of action of latanoprost because this may have negative effects in particular patients (i.e., those with uveitis and cystoid macular edema) for whom caution and close follow-up is necessary.

Commercially available prostaglandin analogs for the reduction of intraocular pressure: similarities and differences

Over the last 12 years, the pharmacological management of glaucoma and ocular hypertension has significantly changed with the introduction of the prostaglandin analogs, specifically, latanoprost, bimatoprost, and travoprost. Their ability to effectively reduce intraocular pressure with once-per-day dosing, their comparable ocular tolerability with timolol, and their general lack of systemic side effects have made them the mainstay of pharmacological therapy for glaucoma and ocular hypertension in most parts of the world. A review of their pharmacology reveals that they are all prodrugs that are converted to their respective free acids within the eye to activate the prostanoid FP receptor and to reduce intraocular pressure by enhancing the uveoscleral and the trabecular meshwork outflow pathways. A review of numerous prospective, randomized comparative studies indicates that no clinically significant differences exist among these agents regarding their ability to lower intraocular pressure.

Mechanism of action of bimatoprost, latanoprost, and travoprost in healthy subjects. A crossover study

PURPOSE

To study the effects of 3 prostaglandin analogs, bimatoprost, latanoprost, and travoprost, on aqueous dynamics in the same subjects and to compare techniques of assessing outflow facility.

DESIGN

Experimental study (double-masked, placebo-controlled, randomized paired comparison, 4-period crossover).

PARTICIPANTS

Thirty healthy adult subjects.

METHODS

Bimatoprost, latanoprost, travoprost, or a placebo was administered to the left eye once a day in the evening for 7 days, after a minimum 4-week washout period between each session. Tonographic outflow facility was measured by Schiøtz tonography and pneumatonography on day 7. On day 8, the aqueous humor flow rate and fluorophotometric outflow facility were measured by fluorophotometry. Uveoscleral outflow was calculated from the aqueous humor flow rate and outflow facility using the Goldmann equation.

MAIN OUTCOME MEASURES

Facility of outflow, aqueous humor flow rate, intraocular pressure (IOP), and calculation of uveoscleral outflow.

RESULTS

All medications lowered IOP relative to a placebo. None of the drugs affected aqueous humor production. All medications increased outflow facility compared with placebo when measured by Schiøtz and 2-minute pneumatonography (P< or =0.02); the apparent increase of outflow facility measured with fluorophotometry and 4-minute pneumatonography did not reach statistical significance. In contrast, uveoscleral outflow was significantly increased by all medications when calculated from 4-minute pneumatonography data, and fluorophotometry and Schiøtz data at higher episcleral venous pressures. The apparent increase found with 2-minute pneumatonography did not reach statistical significance. These differing results in the same patients indicate that differences in measurement techniques, and not differences in mechanism of action, explain previous conflicting published reports on the mechanism of action of the prostaglandins.

CONCLUSIONS

Bimatoprost, latanoprost, and travoprost have similar mechanisms of action. All 3 drugs reduce IOP without significantly affecting the aqueous production rate. All drugs increase aqueous humor outflow, either by enhancing the pressure-sensitive (presumed trabecular) outflow pathway or by increasing the pressure-insensitive (uveoscleral) outflow, but the assessment of the amount of flow through each pathway depends upon the measurement technique.

Comparative Evaluation of Bimatoprost Monotherapy in Primary Chronic Angle Closure and Primary Open Angle Glaucoma Eyes: A Three-Year Study

AIMS

The aim of this study was to compare the long-term efficacy of bimatoprost 0.03% monotherapy in primary open angle glaucoma (POAG) versus primary chronic angle closure glaucoma (PCACG) eyes.

METHODS

A total of 55 consecutive primary adult glaucoma patients on bimatoprost monotherapy were prospectively evaluated in this 3-year, open-labeled, uncontrolled study. The primary outcome was the evaluation of a difference in the response to therapy of POAG eyes, as compared to PCACG eyes over a follow-up of 3 years.

RESULTS

In the POAG group, the mean intraocular pressure (IOP) at the 36-month followup was found to be increased by 2.10 (+/-3.90) mmHg (confidence interval [CI], 0.975-4.185), compared to the mean IOP at 1 month (P = 0.047). In the PCACG group, the mean IOP at the 36-month follow-up was increased by 3.66) (+/- 3.34) mmHg (CI, 6.241-1.092), compared to the mean IOP at 1 month (P = 0.011). This upward drift in IOP was higher in the PCACG group, compared to the POAG group, but this was not statistically significant (P = 0.54). Patients with POAG and PCACG showed a 50% and 40% chance of having an IOP of <18 mmHg with bimatoprost monotherapy (P = 0.23), respectively, at the 3-year follow-up.

CONCLUSIONS

This study showed that bimatoprost 0.03% monotherapy significantly lowers IOP in both POAG and PCACG eyes over a period of 3 years, though its efficacy appeared to decrease over time, to a similar extent, in both groups.

Stability of latanoprost in an ophthalmic lipid emulsion using polyvinyl alcohol

Latanoprost in water is not stable against heat stress due to hydrolysis of the isopropyl ester in the latanoprost molecule. Therefore, the storage condition of latanoprost ophthalmic solution, Xalatan brand, was in a low temperature (2-8 degrees C). We formulated a favorable ophthalmic lipid emulsion of latanoprost using polyvinyl alcohol as emulsifier which showed a good heat stability. The assays of the latanoprost ophthalmic lipid emulsions adjusted to pH 5.0, 6.0 and 7.0 were 100.4%, 100.7% and 99.2% after storage for 4 weeks at 60 degrees C, respectively. The possibility of room temperature storage for the latanoprost ophthalmic lipid emulsion was demonstrated.

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.

Pharmacology and signaling of prostaglandin receptors: multiple roles in inflammation and immune modulation

Prostaglandins are lipid-derived autacoids that modulate many physiological systems including the CNS, cardiovascular, gastrointestinal, genitourinary, endocrine, respiratory, and immune systems. In addition, prostaglandins have been implicated in a broad array of diseases including cancer, inflammation, cardiovascular disease, and hypertension. Prostaglandins exert their effects by activating rhodopsin-like seven transmembrane spanning G protein-coupled receptors (GPCRs). The prostanoid receptor subfamily is comprised of eight members (DP, EP1-4, FP, IP, and TP), and recently, a ninth prostaglandin receptor was identified-the chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2). The precise roles prostaglandin receptors play in physiologic and pathologic settings are determined by multiple factors including cellular context, receptor expression profile, ligand affinity, and differential coupling to signal transduction pathways. This complexity is highlighted by the diverse and often opposing effects of prostaglandins within the immune system. In certain settings, prostaglandins function as pro-inflammatory mediators, but in others, they appear to have anti-inflammatory properties. In this review, we will discuss the pharmacology and signaling of the nine known prostaglandin GPCRs and highlight the specific roles that these receptors play in inflammation and immune modulation.

Mechanism of ocular hypotensive action of bimatoprost (Lumigan) in patients with ocular hypertension or glaucoma

PURPOSE

To determine the mechanism of ocular hypotensive action of bimatoprost in patients with ocular hypertension or glaucoma.

DESIGN

Double-masked, placebo-controlled, randomized, paired comparison crossover study of the effect of bimatoprost on aqueous humor dynamics.

PARTICIPANTS AND CONTROLS

Twenty-nine patients with ocular hypertension or glaucoma.

METHODS

Bimatoprost and a placebo were administered once a day, in the evening, for 7 days before assessment of aqueous dynamics using tonometry, Schiötz tonography, and fluorophotometry. Intraocular pressure (IOP) response to water drinking was measured.

MAIN OUTCOME MEASURES

Aqueous humor flow rate, outflow facility, and IOP.

RESULTS

Intraocular pressure was lowered 29% in the morning and 33% at noon by bimatoprost. Aqueous humor flow was unchanged. Tonographic facility of outflow was increased 47% by bimatoprost relative to the placebo. Assuming an extraocular pressure of 8 mmHg and that extraocular pressure is not altered by bimatoprost, the calculated rate of pressure-insensitive outflow was increased 95% by bimatoprost. During the first hour after water drinking, bimatoprost dampened the IOP rise.

CONCLUSION

As was seen in healthy normal eyes, bimatoprost increased both the pressure-sensitive and the pressure-insensitive outflows of aqueous humor in patients with ocular hypertension or glaucoma. Bimatoprost had no significant effect on aqueous humor formation.

Rate of Response to Latanoprost or Timolol in Patients With Ocular Hypertension or Glaucoma

PURPOSE

This study determined the rate of response to latanoprost compared with timolol in patients with glaucoma or ocular hypertension, whether some patients convert from non-responders to responders after more prolonged therapy, and whether this conversion represents a delayed response or random fluctuation.

METHODS

In a previously described, multicenter, randomized, double-masked, parallel group study, patients received either 0.005% latanoprost once daily (n = 128) or 0.5% timolol twice daily (n = 140) for 6 months. Intraocular pressure (IOP) was assessed at baseline and at 0.5, 1.5, 3, 4.5, and 6 months of treatment at 8 am on all visits, and also at noon and 4 pm at baseline and 6 months. Rate of response based on diurnal measurement at 6 months compared with baseline was assessed using several criteria for response. Eyes with an IOP reduction of less than 15% compared with baseline at 8 am arbitrarily were classified as non-responders at each of the 5 visits during treatment. Consistency of non-responder classifications for individual eyes was assessed.

RESULTS

Mean IOP reduction was greater (P < 0.001) in latanoprost-versus timolol-treated patients throughout the course of therapy. A greater rate of response occurred in patients treated with latanoprost, and differences in response rates between the 2 drugs increased as the definitions of response became more stringent. A greater percentage of non-responders at any single visit were classified as responders at all other visits with latanoprost in comparison with timolol.

CONCLUSIONS

Latanoprost produces a greater rate of response compared with timolol. A higher percentage of non-responders to latanoprost compared with timolol on any individual visit are responders on all other visits. Likewise, a higher proportion of patients who do not initially respond will become responders with continued treatment with latanoprost compared with timolol.

Bimatoprost and travoprost: a review of recent studies of two new glaucoma drugs

Bimatoprost (Lumigan [Allergan, Inc, Irvine CA]) and travoprost (Travatan [Alcon, Ft Worth, TX]) are two new intraocular pressure (IOP)-lowering drugs for use in patients with glaucoma and ocular hypertension. This review evaluates recent studies comparing these new drugs with timolol and with latanoprost. In each study, the statistical analyses support the conclusion that these agents were more effective than timolol and as effective as latanoprost in terms of their ability to reduce IOP. The side effect profiles for bimatoprost, latanoprost, and travoprost were similar, but with statistically higher occurrences of hyperemia and eyelash growth for bimatoprost or travoprost versus latanoprost or timolol.

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.

A comparison of intraocular pressure-lowering effect of prostaglandin F2 -alpha analogues, latanoprost, and unoprostone isopropyl

PURPOSE

To compare the intraocular pressure-lowering effect of unoprostone isopropyl (unoprostone) 0.12% and latanoprost 0.005%. A correlation between the intraocular pressure-lowering effect of unoprostone and latanoprost was also evaluated.

METHODS

A single-masked randomized study included 18 patients between 49 and 68 years (mean, 60.7 +/- 5.1 years) with an intraocular pressure of both eyes from 21 to 27 mm Hg. The patients were prospectively randomized to receive latanoprost in the right eye and unoprostone in the left eye, or unoprostone in the right eye and latanoprost in the left eye. The patients were followed up for 8 weeks. This study evaluated the intraocular pressure-lowering effect and incidence of drug-related side effects.

RESULTS

Mean baseline intraocular pressure was 22.8 +/- 1.2 mm Hg in latanoprost-treated eyes and 22.4 +/- 1.0 mm Hg in unoprostone-treated eyes; there was no statistically significant difference between these groups. Mean intraocular pressure at 8 weeks after the start of the administration was 16.7 +/- 2.0 mm Hg in latanoprost-treated eyes and 19.0 +/- 1.5 mm Hg in unoprostone-treated eyes. Patients in the latanoprost-treated group showed a greater intraocular pressure reduction compared with those in the unoprostone-treated group. Mean intraocular pressure changes in latanoprost-treated eyes were significantly greater at every visit (P < 0.0001). A change of intraocular pressure at 8 weeks in the latanoprost-treated eyes was significantly correlated with that in the contralateral unoprostone-treated eyes (r = 0.665, P = 0.0013) (Figure). There was no significant difference in the rate of ocular side effects between latanoprost- and unoprostone-treated eyes.

CONCLUSIONS

Latanoprost appears to have a more beneficial effect for intraocular pressure control compared with unoprostone. An intraocular pressure reduction in the latanoprost-treated eyes was significantly correlated with that in the contralateral unoprostone-treated eyes. There was no significant difference in the incidence of ocular side effects between both drugs. Further investigation using more cases and longer follow-up periods are needed.

Preclinical efficacy of travoprost, a potent and selective FP prostaglandin receptor agonist

Travoprost is the isopropyl ester prodrug of a high affinity, selective FP prostaglandin full receptor agonist. In contrast to travoprost acid's high affinity and efficacy at the FP receptor, there is only sub-micromolar affinity for the DP, EP1, EP3, EP4, IP, and TP receptors. Travoprost produced a lower incidence of ocular irritation than PGF20 isopropyl ester at a dose of 1 microg in the New Zealand albino (NZA) rabbit. Topical ocular application of travoprost produced a marked miotic effect in cats following doses of 0.01, 0.03 and 0.1 microg. In the ocular hypertensive monkey, b.i.d. application of 0.1 and 0.3 microg of travoprost afforded peak reduction in intraocular pressure (IOP) of 22.7% and 28.6%, respectively. Topical application of travoprost was well tolerated in rabbits, cats and monkeys, causing no ocular irritation or discomfort at doses up to 1 microg. Travoprost is a promising ocular hypotensive prostaglandin FP derivative that has the ocular hypotensive efficacy of PGF2alpha isopropyl ester but with less severe ocular side effects.

Effect of temperature and light on the stability of latanoprost and its clinical relevance

PURPOSE

To examine the effect of controlled heat and ultraviolet exposures on the stability of latanoprost (Xalatan, Pharmacia & Upjohn, Kalamazoo, MI) using high-performance liquid chromatography to derive practical recommendations for patients regarding its use and storage.

METHODS

Using serial dilution of a latanoprost stock solution, varying concentrations were prepared to obtain a standard curve. The accuracy and precision of the high-performance liquid chromatography assay conditions were validated using between-day and within-day studies. The original latanoprost containers were stored at 4, 25, 50, and 70 degrees C, and the concentration of latanoprost remaining was measured by high-performance liquid chromatography at different times for up to 1 month. In addition, the original latanoprost containers were exposed to known amounts of ultraviolet A and B radiation for 4 hours, and the concentration of latanoprost was measured at 1-hour intervals using high-performance liquid chromatography.

RESULTS

The increased temperature studies showed that latanoprost remained stable at 4 and 25 degrees C for the 30-day study duration. Analysis of concentration versus time curves for 50 and 70 degrees C yielded a t90 (time for 10% degradation) of 8.25 and 1.32 days, respectively. Ultraviolet B radiation caused a rapid degradation of latanoprost, whereas ultraviolet A radiation was less effective in causing the degradation of latanoprost.

CONCLUSIONS

Latanoprost exhibits thermal and solar instability and should ideally be stored below room temperature and in the dark. The importance of these storage conditions should be conveyed clearly to the patient.

Potential mechanism for the additivity of pilocarpine and latanoprost

PURPOSE

To determine the ocular hypotensive mechanism underlying the additivity of latanoprost and pilocarpine.

METHODS

This randomized, double-masked study included 30 patients with ocular hypertension on no ocular medications for at least 3 weeks. On each of six visits to the clinic, measurements were taken of aqueous flow and outflow facility by fluorophotometry, intraocular pressure by tonometry, and episcleral venous pressure by venomanometry. Uveoscleral outflow was calculated. Clinic visits were scheduled on baseline day; on day 8 of four times daily pilocarpine (2%) to one eye and vehicle to the other; on day 8 of continued pilocarpine/vehicle treatment plus latanoprost (0.005%) once daily to both eyes; after a 3-week washout period; on day 8 of once-daily latanoprost to one eye and vehicle to the other; and on day 8 of continued latanoprost/vehicle treatment plus pilocarpine four times a day to both eyes. Drug-treated eyes were compared with contralateral vehicle-treated eyes and with baseline day by paired t tests. Combined pilocarpine and latanoprost-treated eyes were compared with individual drug-treated eyes and with baseline day using the Bonferroni test.

RESULTS

Compared with baseline, pilocarpine reduced intraocular pressure from 18.9 to 16.2 mm Hg (P =.001) and increased outflow facility from 0.18 to 0.23 microl per minute per mm Hg (P =.03). No other parameters were affected. Adding latanoprost further reduced intraocular pressure to 13.7 mm Hg (P <.001) and increased uveoscleral outflow from 0.82 to 1.36 microl per minute (P =.02). Latanoprost alone reduced intraocular pressure from 17.6 to 14.3 mm Hg (P <.0001) and increased uveoscleral outflow from 0.89 to 1.25 microl per minute (P =.05). Adding pilocarpine to the latanoprost treatment further reduced intraocular pressure to 12.7 mm Hg (P <.001) and increased outflow facility from 0.21 to 0.30 microl per minute per mm Hg (P =.03).

CONCLUSIONS

Latanoprost and pilocarpine predominantly increase uveoscleral outflow and outflow facility, respectively, when given alone. These drugs are additive because pilocarpine does not inhibit the uveoscleral outflow increase induced by latanoprost.

Effects of 0.005% latanoprost solution on intraocular pressure in healthy dogs and cats

OBJECTIVE

To evaluate effects of daily topical ocular administration of latanoprost solution on intraocular pressure (IOP) in healthy cats and dogs.

ANIMALS

9 domestic shorthair cats and 14 dogs.

PROCEDURE

Latanoprost solution (0.005%) was administered topically to 1 eye (treated) and vehicle to the other eye (control) of all animals once daily in the morning for 8 days. Intraocular pressure was measured twice daily for the 5 days preceding treatment, and IOP, pupillary diameter, conjunctival hyperemia, and blepharospasm were measured 0, 1, 6, and 12 hours after the first 4 treatments and 0 and 12 hours after the final 4 treatments. Measurements continued twice a day for 5 days after treatment was discontinued. Aqueous flare was measured once daily during and for 5 days after the treatment period.

RESULTS

Intraocular pressure and pupillary diameter were significantly decreased in the treated eye of dogs, compared with the control eye. Mild conjunctival hyperemia was also detected, but severity did not differ significantly between eyes. Blepharospasm and aqueous flare were not detected in either eye. Intraocular pressure in cats was not significantly affected by treatment with latanoprost. However, pupillary diameter was significantly decreased in the treated eye, compared with the control eye. Conjunctival hyperemia, aqueous flare, and blepharospasm were not detected in either eye.

CONCLUSIONS AND CLINICAL RELEVANCE

Once-daily topical ocular administration of latanoprost solution (0.005%) reduced IOP in healthy dogs without inducing adverse effects but did not affect IOP in healthy cats. Latanoprost may be useful for treating glaucoma in dogs.

Latanoprost and cystoid macular edema: is there a causal relation?

Published reports of the occurrence of cystoid macular edema (CME) in eyes being treated with latanoprost have led to concern regarding a possible causal relation between the two. Review of all published cases (28 eyes in 25 patients), plus another case reported here for the first time, indicates that all eyes had independent risk for development of CME, so that definitive conclusions about a causal relation cannot be established. In addition, controlled clinical trials and experimental studies with latanoprost have given no indication that latanoprost causes clinical CME. Pharmacokinetic considerations indicate that the concentration of latanoprost expected in the posterior segment of the eye is too low to have a pharmacologic effect, and latanoprost is not known to exhibit vasoactive or inflammatory properties. Nevertheless, reports of a possible association between CME and latanoprost use must be given serious consideration, and in eyes that are at risk for CME, an increased level of surveillance for its development is recommended.

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.

Additive effect of latanoprost and dorzolamide in patients with elevated intraocular pressure

PURPOSE

To evaluate the additive ocular hypotensive effect of latanoprost and dorzolamide in combination, on intraocular pressure reduction in patients with elevated intraocular pressure (IOP).

METHODS

Thirty patients with ocular hypertension or early capsular or primary open-angle glaucoma and elevated IOP were randomly assigned to two parallel treatment groups. The treatment period was twenty days. Fifteen patients (Group 1) received latanoprost once daily during the first ten days and, in addition, dorzolamide three times daily during the second ten days. Fifteen patients (Group 2) received dorzolamide three times daily during the first ten days and, in addition latanoprost, once daily during the second ten days. IOP was measured and conjunctival hyperemia was evaluated.

RESULTS

In Group 1, the mean IOP on day 0 was 26.8 mm Hg; on day 10, 18.7 mm Hg; and on day 20, 15.9 mm Hg. In Group 2, the mean IOP on day 0 was 26.3 mm Hg; on day 10, 21.2 mm Hg; and on day 20, 16.1 mm Hg. Both groups had clinically significant IOP-lowering effect on day 10 as compared with baseline day (30.2% and 19.4% respectively) (p<0.01). When dorzolamide was added to latanoprost, the additional IOP reduction was 2.8 mm Hg (15%) (p<0.01) compared with 5.1 mm Hg (24.1%) (p<0.01) when latanoprost was added to dorzolamide. No local serious adverse reactions were observed. A mild but statistically significant increase in conjunctival hyperemia was seen in latanoprost applied patients.

CONCLUSIONS

The results showed that latanoprost and dorzolamide can be combined successfully to reduce IOP with their additive effects.

Prostaglandin derivates as ocular hypotensive agents

Low doses of naturally occurring prostaglandins reduce the intraocular pressure (IOP) in many species. Species differences do occur both in terms of efficiency and mechanism of action, and also among the different prostaglandins. Among the prostaglandins mainly PGF2 alpha has been tested in human eyes. Although it is an effective ocular hypotensive drug it is not clinically useful due to pronounced ocular side-effects, mainly conjunctival hyperemia and irritation, at doses that produce a maximal effect on IOP. Modification of the drug has resulted in two analogues that are now in clinical use, latanoprost and unoprostone. In long-term studies latanoprost, when applied as a once-daily dose of a 0.005% concentration, reduces IOP at least as effectively as adrenergic beta-receptor blockers. The reduction of IOP is due to increased outflow. This takes place mainly, or exclusively, through the uveoscleral routes, thus introducing a new pharmacological principle for the treatment of glaucoma. The drug reaches systemic concentrations that are below the level expected to stimulate FP-receptors outside the eye and it is rapidly eliminated with a half-life in plasma of 17 minutes, which explains why the clinical trials have not revealed any systemic side-effects with latanoprost. The most frequent side-effect observed with latanoprost is an increased pigmentation of the iris mainly in eyes with irides that are already partly brown. This effect is seen with several naturally occurring prostaglandins and is due to stimulation of melanin production in the melanocytes of the iridial stroma. No structural changes of the melanocytes have been observed in studies performed both in vivo and in vitro. The mechanism of action for unoprostone is the same as for latanoprost. No effect on iris colour has been reported for unoprostone but so far there is limited experience with the drug in eyes with a mixed iris colour.

A comparative study of two dose regimens of latanoprost in patients with elevated intraocular pressure

OBJECTIVE

The purpose of the study was to determine whether latanoprost (13,14-dihydro-17-phenyl-18,19,20-trinor PGF2a-isopropyl ester), a new prostaglandin analogue that has been found effective in reducing intraocular pressure (IOP) in humans, is equally effective at lower concentrations than those currently employed.

DESIGN AND PARTICIPANTS

Fifty patients with glaucoma or ocular hypertension were treated in a randomized, crossover, double-masked fashion with 1 drop of latanoprost (50 microg/ml once daily and 15 microg/ml twice daily) in the affected eye(s) for 3 weeks on each concentration. Tonometry was obtained at 8:00, 13:00, and 17:00 hours at baseline (untreated) and after 3 weeks on each concentration. Placebo (a buffer solution of latanoprost eye drop) was administered for complete masking of the study.

RESULTS

Mean baseline (untreated) diurnal IOP for the entire sample was 24.7 mmHg. Intraocular pressure was reduced by 6.1 mmHg with latanoprost 15 microg/ml twice daily, and by 7.5 mmHg with 50 microg/ml once daily. Results with both regimens were significant (P < 0.001 each, Student's t-test). However, the 50 microg/ml dose was significantly more effective than the 15 microg/ml dose, with a difference of 1.4 mmHg (P < 0.001, ANOVA). Both dose regimens were well tolerated, with little, predominantly mild, ocular discomfort. The higher dose did not cause more hyperemia at 3 weeks than the lower one, i.e., the lower dose yielded a slightly higher score (1.8 mm) on the visual analogue scale (P < 0.29, ANOVA).

CONCLUSIONS

Latanoprost administered at a concentration of 50 microg/ml once daily effectively reduces IOP in patients with elevated IOP. Administration of a lower concentration (15 microg/ml) twice daily is less effective, but still significant.

Additive ocular hypotensive effect of latanoprost and acetazolamide. A short-term study in patients with elevated intraocular pressure

OBJECTIVE

To investigate the additive ocular hypotensive effect of latanoprost on the intraocular pressure (IOP) reduction induced by a suboptimal dose of acetazolamide, a carbonic anhydrase inhibitor.

DESIGN

A short-term, randomized, placebo-controlled, double-masked study.

PARTICIPANTS

Twenty-four patients with glaucoma with elevated IOPs.

INTERVENTION

Acetazolamide 250 mg twice daily from day 1 to day 18. Topical 50 micrograms/ml latanoprost or placebo eye drops bilaterally instilled once daily from day 4 to day 18.

MEAN OUTCOME MEASURES

IOP, conjunctival hyperemia.

RESULTS

The mean IOP of 19.5 mmHg during acetazolamide treatment was further reduced to 16.8 mmHg after topical administration of latanoprost, i.e., a decrease of 2.9 +/- 2.8 mmHg (15%, P < 0.001). Administration of placebo to patients on acetazolamide resulted in an upward drift of 1.3 mmHg (6%, P = 0.03). A modest but statistically significant increase in conjunctival hyperemia was found in the latanoprost-treated group, but did not affect the masking.

CONCLUSIONS

This short-term study indicates that the combination of topically applied latanoprost and a suboptimal dose of systemic carbonic anhydrase inhibitor is useful in the management of glaucoma.

Initial clinical studies with prostaglandins and their analogues

Several prostaglandins (PGs), their prodrugs, and their analogues have been shown to reduce intraocular pressure (IOP) in normotensive volunteers and in patients with elevated IOP. Initial clinical trials demonstrated efficacy with most of these agents, but a PGE2 analogue, PGD2, and BW245C (an analogue selective for the DP-receptor) cause an initial rise in IOP with a minimal subsequent reduction. Although PGF2 alpha tromethamine salt, PGF2 alpha-isopropyl ester (PGF2 alpha-IE), and 15-propionate-PGF2 alpha-IE are all very effective in reducing IOP, they produce unacceptable side effects, including conjunctival hyperemia and ocular irritation. Isopropyl unoprostone, a 22-carbon chain PGF2 alpha metabolite, produces a 10-25% reduction in IOP lasting approximately 2-5 hours, is well tolerated, and is commercially available for use in Japan. 17-phenyl substituted PGF2 alpha-IE analogues, such as PhXA34 or latanoprost, effectively reduce IOP by 30-40% for at least 24 hours, and are very well tolerated with minimal conjunctival hyperemia and without irritation. Latanoprost is the more potent 15R-epimer of PhXA34, and has become a useful agent in glaucoma therapy.

Effects of exogenous prostaglandins on aqueous humor dynamics and blood-aqueous barrier function

Topical prostaglandins (PGs) are very effective at reducing intraocular pressure (IOP) in a variety of animals and in humans with relatively few side effects. The mechanisms of action of several PGs, their prodrugs and analogues have been studied in rabbits, cats, monkeys and humans. PGF2 alpha and its analogues evaluated in monkeys include PGF2 alpha-tromethamine salt, PGF2 alpha -isopropylester (-IE), S-1033, PhXA34, PhDH100A and latanoprost (PhXA41). Aqueous flow and outflow facility are either increased or remain unchanged by these agents. PGF2 alpha-IE, PHXA34, PhDH100A and latanoprost increase uveoscleral outflow, accounting for most of the IOP reduction. PGA2 in cats increases aqueous flow and outflow facility, but it reduces IOP primarily by stimulating uveoscleral outflow. The PGD2 analogue BW245C is unique in that it is the only PG that decreases aqueous flow. Mechanistic studies in humans have been performed with PGF2 alpha -IE, unoprostone, PhXA34 and latanoprost. In two clinical studies with latanoprost, a significant increase in uveoscleral outflow was found which, as in animals, accounts for most of the IOP reduction. A slight but inconsistent increase in outflow facility may also be involved. The doses tested had minimal effects on the permeability of the blood-aqueous barrier (BAB). In vitro studies of human tissue have been conducted to elucidate the PG effect on outflow facility and uveoscleral outflow. Studies of isolated human anterior segment preparations show that PGE2 increases outflow facility whereas PGF2 alpha has no measurable effect on this parameter. Studies of human ciliary muscle cells in tissue culture indicate that PGs may directly modulate extracellular matrix metabolism, which may be related to the increased uveoscleral drainage. This review summarizes in vitro and in vivo studies of the effects of PGs on aqueous humor dynamics and BAB integrity in humans, cats and monkeys.

Comparison of latanoprost and timolol in patients with ocular hypertension and glaucoma: a six-month masked, multicenter trial in the United States. The United States Latanoprost Study Group

PURPOSE

Latanoprost, a new prostaglandin analogue, was compared with timolol for ocular hypotensive efficacy and side effects.

METHODS

In a multicenter, randomized, double-masked, parallel group study, 268 patients with ocular hypertension or early primary open-angle glaucoma received either 0.005% latanoprost once daily or 0.5% timolol twice daily for 6 months. All except ten patients from each group successfully completed the study.

RESULTS

Intraocular pressure (IOP) was significantly (P<0.001) reduced and maintained by both medications without evidence of a long-term drift over 6 months. Comparing 6-month with baseline diurnal IOP values, the IOP reduction (mean +/- standard deviation) achieved with latanoprost (-6.7 +/- 3.4 mmHg) was significantly (P<0.001) greater than that produced with timolol (4.9 +/- 2.9 mmHg). Four patients treated with timolol and none treated with latanoprost were withdrawn from the study because of inadequate IOP control. Pulse rate was significantly reduced with timolol, but not with latanoprost. Slightly more conjunctival hyperemia appeared in latanoprost-treated compared with timolol-treated eyes. Fewer subjective side effects occurred in latanoprost-treated eyes. Both eyes of a patient with a characteristic, concentric iris heterochromia (darker centrally) at baseline showed a definite, photographically documented increase in pigmentation during latanoprost treatment, making the irides uniformly darker. Three additional patients treated with latanoprost were suspects for this color change. Otherwise, no significant difference between treatment groups occurred visual acuity, slit-lamp examination, blood pressure, and laboratory values.

CONCLUSION

Latanoprost has the potential for becoming a new first-line treatment for glaucoma.

PGF2 alpha/pilocarpine interactions on IOP and accommodation in monkeys

We investigated whether (i) single or repeated topical treatment with either the tromethamine salt or the isopropyl ester of prostaglandin F2 alpha (PGF2 alpha-TS or PGF2 alpha-IE) inhibits the accommodative response to pilocarpine; (ii) pilocarpine given after PGF2 alpha inhibits the latter's ocular hypotensive effect, as occurs with the reverse order of administration. PGF2 alpha-IE (2 micrograms) or PGF2 alpha-TS (50 micrograms) was applied topically to the right eye of five cynomolgus monkeys twice daily for 4 days. Before initial dosing, and 1 hr after the initial and final dose the animals were anesthetized with ketamine, and intraocular pressure (IOP) and refraction determined bilaterally. Following post-PG IOP and refraction determinations, pilocarpine HCl was given topically (bilaterally) or infused i.m. over 10 min, after which refraction was determined periodically for 50 min. IOP was then again determined. After a single unilateral dose of PGF2 alpha-TS or PGF2 alpha-IE, IOP was unchanged. Both eyes accommodated markedly and equally in response to pilocarpine, and IOP fell bilaterally by a statistically significant 3 mmHg in response to pilocarpine. Repeated doses of PGF2 alpha-TS or PGF2 alpha-IE did not significantly affect the accommodative response to pilocarpine, while pilocarpine did not alter the approximately 10 mmHg ipsilateral IOP fall induced by repeated dosing of PGF2 alpha-TS or PGF2 alpha-IE. It is concluded that repeated unilateral topical application of PGF2 alpha-TS or PGF2 alpha-IE to the cynomolgus monkey eye markedly reduces ipsilateral IOP, but has no effect on the ipsilateral or contralateral eye accommodative response to pilocarpine. Pilocarpine reverses the PGF2 alpha-TS or PGF2 alpha-IE-induced fall in IOP when given before the PGF2 alpha, but does not prevent it when given after, within the parameters of this study.

Additive effect of latanoprost, a prostaglandin F2 alpha analogue, and timolol in patients with elevated intraocular pressure

A randomised observer masked clinical study was conducted to assess the additive effect of latanoprost (13,14-dihydro-17-phenyl-18,19,20-trinorprostaglandin F2 alpha-isopropylester) to timolol maleate in patients with elevated intraocular pressure (IOP). Patients were randomly assigned to two treatment groups. One group (n = 10) received timolol, the other group (n = 9) received latanoprost twice daily for 1 week. After 1 week all patients received both timolol and latanoprost. Eyes treated with timolol (mean diurnal IOP (SD) day 0, 24.2 (2.8) mm Hg) and latanoprost (mean diurnal IOP day 0, 28.5 (5.6) mm Hg) showed an IOP reduction of 5.9 (2.3) mm Hg (24%) and 8.9 (2.5) mm Hg (31%), respectively after the first week. Adding latanoprost to the eyes treated with timolol as well as timolol to the eyes receiving latanoprost gave a further reduction of 2.6 (1.1) mm Hg (13%) and 2.6 (2.2) mm Hg (14%), respectively. Only mild transient hyperaemia was observed in patients receiving latanoprost. The results indicate that latanoprost and timolol can be combined successfully and that complete or almost complete additivity is reached even at pressure levels below 20 mm Hg.