Timolol--further observations

Paradoxical response to carbonic anhydrase inhibitors in patients with intraretinal cystoid spaces

Background: Intraretinal cystoid spaces (IRCS) are fluid-filled spaces seen in some retinal dystrophies and often treated with carbonic anhydrase inhibitors. The purpose of this study is to report an unexpected bilateral improvement in the IRCS after discontinuation of therapy. Material and Methods: We identified from our records 23 patients with retinal dystrophy and IRCS who had been treated with topical and/or oral carbonic anhydrase inhibitors. All subjects had regular follow-up with OCT and previous genetic testing. Results: We identified four (17%) patients who experienced a bilateral and symmetrical paradoxical improvement in IRCS size and visual acuity after discontinuation of carbonic anhydrase inhibitors. Two were mutations in RS1, one in CLN3 and another in NR2E3. All patients were followed for at least three years (range 39-63 months). None had systemic abnormalities. Conclusions: Patients with IRCS may exhibit a paradoxical response after discontinuation of carbonic anhydrase inhibitors. Although the pathophysiology of these phenomena is unclear, stopping treatment may be an option in patients who cease to improve or get worse on treatment.

Effect of preserved and preservative-free timolol eye drops on tear film stability in healthy Africans

Background:

Preserved versus nonpreserved formulations for ophthalmic use have been well described in the literature although not specifically in the African population where beta blockers are frequently used as the first-line therapy due to economic and availability issues. This study sought to determine the effect of preserved and preservative-free Timolol eye drops on tear film stability in healthy black Africans.

Materials and Methods:

Sixty healthy nondry eye subjects aged 19–25 years were randomly assigned into four groups (n = 15) and differently treated with eye drops of phosphate buffered saline (PBS), preservative-free timolol (PFT), benzalkonium chloride (BAK) only, and BAK-preserved timolol (BPT). Noninvasive tear break-up time (NITBUT) was measured using the keratometer at baseline and 30, 60, and 90 min after drop application.

Results:

No significant decline in NITBUT was observed following treatment with PFT and PBS. However, BAK treatment showed a positive time-dependent significant decline in NITBUT (P < 0.001) while a significant decline in the BPT-treated group was only found at 90 min (−3.52 s; P < 0.001). In comparison to the PFT-treated group, treatment with BAK and BPT showed significantly lower NITBUT (P < 0.001).

Conclusion:

BPT is associated with a significant decline in tear film stability in black Africans. This finding has implications in the management of glaucoma in patients with high-risk of dry eyes in this population.

Effect of preservative removal from fixed-combination bimatoprost/timolol on intraocular pressure lowering: a potential timolol dose-response phenomenon

PURPOSE

Many patients with glaucoma require combination therapies to achieve target intraocular pressure (IOP) and preserve visual function. Ocular hypotensives often contain a preservative (eg, benzalkonium chloride [BAK]), but preservative-free (PF) formulations have been developed for patients with sensitivity. A Phase III study found the efficacy of bimatoprost 0.03%/timolol 0.5% (bim/tim, Ganfort(®)) PF to be equivalent to that of preserved bim/tim, although a trend favoring bim/tim PF was observed. As BAK is a corneal penetration enhancer, this literature review aims to explain these findings by exploring the relationship between timolol concentration and its IOP-lowering effect.

METHODS

Systematic searches were performed in Scopus and PubMed for clinical trials published in English between 1960 and July 2014 using the keywords "timolol", "intraocular pressure", and the concentrations "1%, 0.5%, OR 0.25%". Articles that directly compared IOP-lowering effects of ≥2 concentrations of timolol were identified by manual screening, and cross-checked for duplication.

RESULTS

Seventeen studies that included 10-371 patients were evaluated; the majority were randomized (16/17), double-masked (14/17), and enrolled patients with open-angle glaucoma or ocular hypertension (12/17). All studies investigated timolol in preserved formulations. Timolol concentrations tested ranged from 0.008% to 1.5%. Of 13 studies comparing timolol 0.25% versus 0.5%, two found the 0.25% dose to have greater IOP-lowering effects, and three reported the opposite; eight reported similar IOP lowering. Results also indicate that timolol 0.5% may be more effective than higher concentrations.

CONCLUSION

The evidence suggests that timolol may have an inverted U-shaped dose-response curve, and that its optimal IOP-lowering concentration is between 0.25% and 0.5%. Compared with bim/tim, removal of the permeability enhancer BAK in bim/tim PF could have resulted in a lower timolol concentration at the target site, bringing the effective concentration within the 0.25%-0.5% range and enhancing the efficacy of bim/tim PF.

Efficacy of a preservative-free formulation of fixed-combination bimatoprost and timolol (Ganfort PF) in treatment-naïve patients vs previously treated patients

PURPOSE

To evaluate, using subgroup analysis, the effect of treatment status on the intraocular pressure (IOP)-lowering efficacy of a preservative-free formulation of fixed-combination bimatoprost 0.03%/timolol 0.5% (FCBT PF).

METHODS

A primary, multicenter, randomized, double-masked, 12-week study compared the efficacy and safety of FCBT PF with preserved FCBT (Ganfort(®)) in 561 patients diagnosed with glaucoma or ocular hypertension. For this analysis, eligible patients were treatment-naïve or had inadequate IOP lowering and underwent a washout of previous treatment. IOP (8 am, 10 am, and 4 pm) was measured at baseline and weeks 2, 6, and 12. Subgroup analysis of the FCBT PF arm assessed changes in average eye IOP from baseline in treatment-naïve vs previously treated patients. To evaluate the effect of treatment status at baseline (treatment-naïve vs previously treated) on IOP reduction in the FCBT PF treatment group, an analysis of covariance model was used with treatment status and investigator as fixed effects, and baseline average eye IOP, age, glaucoma diagnosis, and baseline average eye corneal thickness as covariates. P-values and the 95% confidence intervals were determined using the model.

RESULTS

In the FCBT PF arm, IOP mean changes from baseline ranged from -8.7 mmHg to -9.8 mmHg in treatment-naïve patients (N=50), compared with -7.3 mmHg to -8.5 mmHg in previously treated patients (N=228). Baseline IOP, age, glaucoma diagnosis, and corneal thickness significantly affected IOP reduction in the FCBT PF group. Adjusting for these covariates, FCBT PF had a greater IOP-lowering effect (0.8-1.7 mmHg) in treatment-naïve patients than previously treated patients, which was statistically significant (P≤0.05) at seven of nine time points.

CONCLUSION

In this subgroup analysis, FCBT PF reduced IOP more effectively in treatment-naïve than in previously treated patients possibly due, in part, to altered responsiveness or tachyphylaxis that has been associated with prior ocular hypotensive agent treatment.

Intraocular pressure after replacement of current dual therapy with latanoprost monotherapy in patients with open angle glaucoma

AIMS

To evaluate the efficacy and safety of replacing current dual ocular hypotensive therapy with latanoprost 0.005% monotherapy in patients with open angle glaucoma.

METHODS

This randomised, open label, parallel group, multinational study included 466 patients with open angle glaucoma currently on dual ocular hypotensive therapy, including a beta adrenergic receptor antagonist. Patients were assigned (1:3) to ongoing dual therapy or a switch to monotherapy with latanoprost 0.005% once daily for 6 months. Intraocular pressure (IOP) was measured at 10 am and 5 pm at baseline, month 3, and month 6. Groups were compared for differences in diurnal IOP change, IOP success rates (IOP < or =22 mm Hg with < or =15% increase from baseline), and clinical success rates (not requiring change in therapy).

RESULTS

Baseline mean diurnal IOP was 17.8 (SD 2.0) mm Hg in the latanoprost group and 17.6 (2.1) mm Hg in the dual therapy group. After 6 months, mean diurnal IOP was reduced by 0.26 (0.18) (SEM 1.4%) mm Hg (p=0.153) in the group switched to latanoprost and by 0.37 (0.25) (2.1%) mm Hg (p=0.138) in those continuing dual therapy (difference: 0.11 mm Hg; p=0.641). Success rates defined by IOP criteria were 83% for latanoprost and 89% for continued dual therapy (difference: 6%; p=0.122). Clinical success rates were 97% for latanoprost and 99% for dual therapy (difference: 2%; p=0.161). Ocular adverse events were reported by 23% of patients in both treatment groups.

CONCLUSION

Latanoprost monotherapy is a safe and effective alternative for many patients with open angle glaucoma requiring dual topical ocular hypotensive therapy for IOP control.

Persistency and clinical outcomes associated with latanoprost and beta-blocker monotherapy: evidence from a European retrospective cohort study

PURPOSE

To evaluate persistency (time on initial therapy) and the clinical impact of latanoprost versus beta-blocker monotherapy in treating glaucoma.

METHODS

This observational, multicenter, retrospective medical chart review study conducted in four European countries included patients with primary open-angle glaucoma or ocular hypertension who began their first glaucoma treatment with latanoprost or a beta-blocker between November 1996 and November 1998. Persistency and glaucoma-related clinical outcomes data were abstracted for the 2 years following treatment initiation.

RESULTS

In all, 260 patient charts were analyzed (94 latanoprost, 166 beta-blocker). Patients in the latanoprost group stayed on therapy twice as long as those who received a beta-blocker (p < 0.0001). After adjusting for baseline characteristics, patients receiving a beta-blocker as initial therapy were 3.8 times more likely to change therapy than those initially treated with latanoprost (p < 0.0001). Patients in the latanoprost group also experienced greater mean decreases in intraocular pressure (IOP) than those receiving a beta-blocker (7.4 mmHg versus 4.6 mmHg, respectively; p < 0.0001), and fewer had worsened optic nerve head excavation (1.7% versus 14.2%, respectively; p < 0.05) by the time of their first therapy change or last study visit, whichever came first.

CONCLUSIONS

Over a 2-year period, latanoprost was associated with significantly greater persistency and better clinical IOP outcomes compared with beta-blocker therapy.

Pharmacological therapy for glaucoma: a review

For some time the medical treatment of glaucoma has consisted of topical beta-blockers, adrenergic agents, miotics and oral carbonic anhydrase inhibitors (CAIs). However, the therapeutic arsenal available for the medical treatment of glaucoma has recently extended with new classes of ocular hypotensive agents i.e. prostaglandins, local CAIs and alpha2-adrenergic agents. Beta-blockers are still the mainstay in glaucoma treatment and are first line drugs. However, even if they are applied once daily, as with timolol in gel forming solution and levobunolol, the possible cardiopulmonary adverse effects of beta-blockers remain a cause for concern. When monotherapy with beta-blockers is ineffective in reducing intraocular pressure (IOP) or is hampered by adverse effects, a change of monotherapy to prostaglandins, local CAIs, alpha2-adrenergic agonists (brimonidine) or to dipivalyl epinephrine is advised. Prostaglandins, local CAIs and alpha2-adrenergic agonists, such as brimonidine, may in time become first line drugs because they reduce IOP effectively and until now systemic adverse effects have rarely been reported with these agents. The development of a pro-drug of either a local CAI or an alpha2-adrenergic agonist with a sustained and continuous effect on IOP level, which could be applied once a day is suggested. Because of these new developments, miotics, i.e. pilocarpine and carbachol, are recommended as second or third line drugs. The cholinesterase inhibitors are considered third line drugs as better agents with fewer local and systemic adverse effects have become available. Oral CAIs may be used temporarily in patients with elevated IOPs e.g. postsurgery or post-laser, or continuously in patients with glaucoma resistant to other treatment. Combining ocular hypotensive drugs is indicated when the target pressure for an individual patient cannot be reached with monotherapy. Combination therapy of beta-blockers is additive with prostaglandins, topical CAIs and miotics. Prostaglandins such as latanoprost can be combined with beta-blockers, adrenergic agents, local CAIs and miotics. Combinations with brimonidine or local CAIs need further investigation. Treatment of glaucoma with the new ocular hypotensive agents, either in monotherapy or combination therapy, may provide lower IOPs and delay or postpone the need for surgery.

Efficacy and safety of timolol/pilocarpine combination drops in glaucoma patients

The aim of this randomized, double-blind study with two parallel groups was to examine the safety, efficacy and tolerability of two combination eye drops containing 0.5% timolol and 2% pilocarpine (Fotil, Leiras, Finland, and Timpilo, MSD, USA) in patients with glaucoma or ocular hypertension. Efficacy was determined based on daytime intraocular pressure curve and safety by examining visual fields, visual acuity, optic discs, by determining blood pressure and pulse rate, and by performing Schirmer and fluorescein tests. A total of 89 patients were enrolled, and 71 completed the 10-week treatment period. This study showed that the two combinations of 0.5% timolol maleate and 2% pilocarpine HCl compared in this study were equally effective in reducing intraocular pressure. The decrease in mean daily intraocular pressure from 0 to 10 weeks was 7.48 mmHg for Fotil, and 6.31 for Timpilo. The mean decrease in mean daily intraocular pressure was 29.3% for Fotil, and 26.0% for Timpilo. No significant differences were found between the groups. Adverse event were reported by 70 out of 89 patients by the end of 2 weeks, but were severe enough only in 11 for the treatment to be discontinued. In all others, adverse events were of transient nature and considered mild. In general, adverse events were similar in both study groups. However, burning was more common in patients on Fotil, and blurring of vision and light sensitivity were more common in patients on Timpilo. In patients with no contraindication to beta-blockers, these drugs appeared to be safe.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic response interactions between timolol maleate and dipivefrin hydrochloride

Twenty-one patients on long-term treatment with topical timolol maleate and dipivefrin hydrochloride were studied to assess the effect of each agent when used in combined therapy. The two agents are partially additive in most patients, but the relative contribution of each agent varies widely in individual patients and in separate diagnostic categories.

Topical timolol, at conventional, unilateral doses causes bilateral ocular beta-blockade in rabbits

The studies described herein reveal that unilateral 0.3% and 1% doses of timolol produce marked beta-adrenoceptor blockade in treated and in contralateral eyes which did not receive timolol. This indicates that unilateral, conventional topical doses of timolol administered to rabbits cause bilateral ocular beta-adrenoceptor blockade. In addition, 0.1% and 1% doses of timolol applied to one eye resulted in blockade of cardiovascular beta-adrenoceptors. Thus, the most likely explanation for bilateral ocular beta-blockade would be systemic absorption of timolol from the treated eye and redistribution to the fellow eye. Since contralateral eyes would not provide an adequate control in circumstances where a large dose of timolol is administered unilaterally, caution must be exercised in interpreting data obtained in laboratory animals with doses of timolol similar to those employed clinically. A 0.01% dose of timolol appears adequate to achieve marked, unilateral ocular beta-adrenoceptor blockade in rabbits.

Efficacy of combining timolol with other antiglaucoma medications

The ocular hypotensive effects of timolol and a carbonic anhydrase inhibitor (acetazolamide or methazolamide) are partially additive; that is, concurrent administration of these drugs produces a clinically useful reduction in intraocular pressure which is greater than the effect of either medication alone, but less than the arithmetic sum of the effects of the individual drugs. Similarly, concurrent administration of timolol and a miotic agent (pilocarpine, carbachol, or echothiophate iodide) produces a clinically useful response in most glaucoma patients. In contrast, the ocular hypotensive effects of timolol and epinephrine are poorly additive. Only a minority of patients maintain a substantial, longterm reduction in intraocular pressure when timolol is added to a regimen of epinephrine or vice versa. Ophthalmologists prescribing timolol or epinephrine for patients receiving the other drug are urged to use a therapeutic trial to one eye for several weeks to determine the efficacy of concurrent treatment. The addition of timolol to the medical regimen of patients uncontrolled on maximum tolerated antiglaucoma therapy (a miotic agent, epinephrine and a carbonic anhydrase inhibitor) reduces intraocular pressure substantially in one-third to one-half of the cases.

Pharmacokinetics of topically applied ophthalmic drugs

Pharmacokinetic applications in recent years have led to significant advances in systemic drug therapy, but applications to topical, ophthalmic therapy have been far less numerous. Pharmacokinetics is the study of the time course of the absorption, distribution, metabolism, and elimination of an administered drug. Thus, it includes the quantitation of such elements of drug bioavailability as tear dilution, drug binding, and vehicle effects; factors affecting corneal absorption and subsequent tissue distribution; dosage form effects; and pathways of elimination. These factors are important because they significantly influence the clinical responses to administered drugs, in some instances to a profound degree. These elements and their clinical implications are discussed along with some recent applications, exemplified with data from studies on frequently prescribed drugs.

The beta-adrenergic blocking agents and the treatment of glaucoma

The autonomic nervous system is divided into the parasympathetic and sympathetic systems, with three types of adrenergic receptors: alpha (smooth muscle contraction), beta1 (cardiac acceleration and fatty acid mobilization) and beta2 (smooth muscle relaxation). Substances affecting the function of the adrenergic system are the agonists or stimulators, which mimic the effects of endogenous norepinephrine or epinephrine, and antagonists or blockers, which block the receptors and prevent stimulation by the agonists. Autonomic stimulation in the eye mediates various changes which apparently affect outflow facility and rate of formation of aqueous humor. Alteration of either or both of these factors by autonomic agonists or antagonists may have a direct or an indirect effect on intraocular pressure. Beta-adrenergic blocking substances have been used to treat a variety of diseases. Some of the effects of these drugs are attributable to properties other than beta blockade, such as intrinsic sympathomimetic activity and local anaesthetic activity. Side effects of this class of drugs require caution in cases of congestive heart failure and in asthmatics. Autonomic agents used in the treatment of ocular hypertension and glaucoma include pilocarpine, a chilinergic agonist, epinephrine, an adrenergic agonist, and various beta adrenergic blockers or antagonists including propranolol, atenolol and timolol. The physico-chemical properties and pharmacokinetics of timolol are reviewed. Data showing a significant reduction in intraocular pressure as a result of ocular instillation of timolol are presented. Reduction of the rate of aqueous formation appears to be the mechanism of action. A low incidence of non-serious side effects is reported.