Effect of timolol 0.5% gel and solution on pulmonary function in older glaucoma patients

Pharmacotherapy and Adherence Issues in Treating Elderly Patients with Glaucoma

Glaucoma is a leading cause of visual morbidity throughout the world and is an age-related condition, the prevalence of which rises significantly with increasing age. Glaucoma, a condition affecting the optic nerve, has a variety of subtypes with multiple aetiological factors, the most important of which are intraocular pressure (IOP) and increasing age. Treatment by lowering of IOP is the only current method, for which there is evidence, by which the rate of progressive visual deterioration can be slowed or halted. Although there are surgical and laser treatments that are efficacious in lowering IOP, the most common manner in which patients with glaucoma control their IOP is with administration of daily topical ocular hypotensive drugs (eye drops). The variety of topical drugs utilised in the management of glaucoma all have the potential to have adverse effects and/or interactions with concomitant medications, many of which may be used for other age-related conditions. Adherence with appropriate medicines has a major effect on the outcome of medical conditions and this aspect applies to the management of glaucoma. There are certain specific issues that relate to the administration of topical agents, with respect to both adverse effects and adherence. Although many suspect poor adherence in elderly patients with glaucoma, relative to younger patients, adequate evidence for this is lacking. Furthermore, the manner by which adherence issues could be improved remains inadequately understood and poorly addressed. The aims of this article were to review, from a clinical perspective, the medical therapies currently used for glaucoma and discuss adherence issues with respect to the population of patients with glaucoma, who tend to be relatively elderly.

Association between Ophthalmic Timolol and Hospitalisation for Bradycardia

Introduction. Ophthalmic timolol, a topical nonselective beta-blocker, has the potential to be absorbed systemically which may cause adverse cardiovascular effects. This study was conducted to determine whether initiation of ophthalmic timolol was associated with an increased risk of hospitalisation for bradycardia. Materials and Methods. A self-controlled case-series study was undertaken in patients who were hospitalised for bradycardia and were exposed to timolol. Person-time after timolol initiation was partitioned into risk periods: 1–30 days, 31–180 days, and >180 days. A 30-day risk period prior to initiating timolol was also included. All remaining time was considered unexposed. Results. There were 6,373 patients with at least one hospitalisation for bradycardia during the study period; 267 were exposed to timolol. Risk of bradycardia was significantly increased in the 31–180 days after timolol initiation (incidence rate ratio (IRR) = 1.93; 95% confidence interval (CI) 1.00–1.87). No increased risk was observed in the first 30 days or beyond 180 days of continuous exposure (IRR = 1.40; 95% CI 0.87–2.26 and IRR = 1.21; 95% CI 0.64–2.31, resp.). Conclusion. Bradycardia is a potential adverse event following timolol initiation. Practitioners should consider patient history before choosing a glaucoma regime and closely monitor patients after treatment initiation with topical nonselective beta-blocker eye drops.

Ophthalmic timolol: plasma concentration and systemic cardiopulmonary effects

Timolol maleate is a non-selective beta-adrenoceptor antagonist currently used mainly as an ocular preparation for the treatment of glaucoma and ocular hypertension. Despite the topical administration, ophthalmic timolol causes systemic adrenergic beta-blocking because of absorption from the eye into the systemic circulation. Gel formulations of ophthalmic timolol have been developed to reduce systemic absorption and adverse effects in comparison with conventional aqueous solution formulations. Timolol is metabolized by the polymorphic cytochrome P450 2D6 enzyme (CYP2D6). The changes in heart rate (HR) are the most striking effects of the systematically absorbed fraction of ophthalmic timolol, with 0.5 % aqueous formulations presenting larger effects than 0.1 % hydrogel formulations, especially during exercise. Plasma levels of ophthalmic timolol correlate with the changes in HR. Neither 0.5 % aqueous nor 0.1 % hydrogel formulations of timolol have exerted noteworthy effects on systolic (SAP) or diastolic (DAP) arterial pressures, probably because of a compensatory increase in systemic vascular resistance due to the attenuation of HR. Ophthalmic timolol does not exert remarkable effects on pulmonary parameter peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV1) in non-asthmatic patients. CYP2D6 activity is clearly associated with the pharmacokinetic parameters, particularly when 0.5 % aqueous solution of timolol is used: peak plasma concentration, elimination half-life and area-under-the-curve are highest in CYP2D6 poor metabolizers. Finally, since there is a correlation between the plasma level of timolol and several haemodynamic effects - especially HR in the state of elevated beta-adrenergic tonus - the CYP2D6 poor metabolizers may be more prone to bradycardia during treatment with (aqueous) ophthalmic timolol.

Efficacy and systemic side-effects of topical 0.5% timolol aqueous solution and 0.1% timolol hydrogel

PURPOSE

The objective of this randomized, double-blind, controlled crossover trial was to compare 0.1% timolol hydrogel formulation eyedrops with 0.5% timolol aqueous solution in terms of systemic effects, hypotensive efficacy and pharmacodynamics.

METHODS

Twenty-four healthy subjects underwent careful ocular, cardiovascular and pulmonary function evaluation before and after 2 weeks of topical treatment with 0.1% timolol hydrogel or 0.5% aqueous timolol maleate. Intraocular pressure (IOP), heart rate, blood pressure, forced expiratory volume and plasma levels of timolol were measured.

RESULTS

There was a statistically significant difference in the systemic absorption of timolol between these two ophthalmic timolol solutions. The peak concentration and mean area under the plasma drug concentration-time curve (AUC) were about 10-fold higher after 0.5% timolol aqueous solution. The mean peak heart rate during exercise was reduced by 19 bpm (SD 6.4 bpm) after 0.5% timolol aqueous solution and by only 4.6 bpm (SD 3.8 bpm) after 0.1% timolol hydrogel (p < 0.0001). There was no difference between the two formulations in efficacy in reducing IOP. No differences between treatments were found in respect of pulmonary function.

CONCLUSIONS

The lower timolol concentration in the hydrogel vehicle and its better bioavailability resulted in reduced systemic absorption and side-effects without loss of efficacy.

Glaucoma Medications

As with many diseases, glaucoma increases in frequency in older populations, and is very often encountered in patients taking multiple medications. While the exact mechanism of glaucomatous optic neuropathy (GON) is not known, intraocular pressure (IOP) is thought to be central to the process, and reducing IOP is the only known effective treatment. The newer definition of glaucoma is an IOP-sensitive optic neuropathy. While large, controlled studies have indicated that reducing IOP will slow the progression of disease, the contributions of other conditions and medications have not been adequately studied. As the adverse effect profiles of medical therapies for glaucoma have improved, use of these agents has increased greatly. This has resulted in a large number of older patients taking glaucoma medications. Since topical medications can easily be overlooked in a medical history, and are for the most part well tolerated, systemic complications from these agents can be missed. In addition to being a common disease requiring treatment, glaucoma is also a model system for other degenerative diseases, and many of the concepts originally developed in relation to neurodegenerative diseases such as Alzheimer's disease are under investigation for glaucoma. These include approaches targeted towards neuroprotection and excitotoxicity.