Polymeric pseudolatices bearing pilocarpine for controlled ocular delivery

The pseudolatex-based ocular formulations of pilocarpine were prepared using different combinations of Eudragit RS 100 and polyvinyl pyrrolidone for prolonged and controlled release of the drug. The designed system was essentially based on polymeric pseudolatex dispersion. The process variables that effect the latex particle size, drug loading and release profiles of drug were studied. Preparations were evaluated for their in vitro performance with regard to release profile and diffusion co-efficient. The designed system exhibited linear relationship between cumulative drug release (Q) and square root of time (t0.5). The products selected on the basis of in vitro characterization were studied for in vivo performance evaluation. It was observed that the preparations exhibited in vivo prolonged therapeutic efficacy. Thus polymer based pseudolatices hold promise for controlled pilocarpine ocular delivery.

Three avian eye enlargement protocols as myopia models: effects of pharmacological intervention

Myopia is a prevalent condition threatening vision in half or more of the individuals in some subpopulations and at some ages. The etiology is unknown. It is not even clear whether myopia has several possible causes or only one, whether the condition is inherited or acquired. Suggested counter measures have ranged from behavior modification during the growing years through various medications, to surgical intervention. It is suggested that answers to these questions must lie in research exploring how the eye develops, how it serves its owner. A common finding in most cases of myopia is that the eyeball is too long axially, thus the image from a distant object comes to sharp focus in front of, rather than at, the retina. Accommodation increases the refractive power of the eye and is counterproductive in a myope. Nonetheless, one suggested treatment has been to suppress accommodation by paralyzing the ciliary muscles. Another theory suggests that high intraocular pressure causes eye enlargement, thus the anti-glaucoma drugs have sometimes been recommended. We report here some trials involving drugs given to chicks with light-induced avian glaucoma, a syndrome characterized by moderate to severe myopia, and elevated intraocular pressure.

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.

Miotics: side effects and ways to avoid them

Pilocarpine, a parasympathomimetic drug used in the treatment of glaucoma, produces a variety of ocular and systemic adverse reactions. Ocular side effects include miosis, accommodative spasm, frontal headaches, twitching lids, conjunctival injection, cataractous changes, allergic reactions, iris cysts, retinal detachment, increased permeability of the blood-aqueous barrier, anterior chamber narrowing, and the potential for inducing an acute angle-closure attack. Systemic side effects include nausea, vomiting, tenesmus, abdominal spasm, salivation, lacrimation, sweating, pulmonary edema, and bronchial spasm. The systemic side effects can best be minimized initially through proper use of the medication and nasolacrimal occlusion. The Ocusert, a long-acting pilocarpine-incorporated ocular insert, is a recent advance in delivery technique that offers an adequate hypotensive action with fewer side effects. Pilopex is a promising new experimental pilocarpine polymer salt presently being studied in Israel. Photomydriasis, a process involving the use of a laser to enlarge miotic pupils also offers help for these patients. N-demethylated carbachol is a new parasympathomimetic drug currently under study for glaucoma therapy. Initial results show that it may have considerable ocular hypotensive action with fewer adverse effects.

The uniocular therapeutic trial in the management of elevated intraocular pressure

A trial of topical therapy in one eye is advocated as part of the evaluation of the patient with elevated intraocular pressure. This will determine the effectiveness of pressure reduction and the side effects that can be expected. The results of such a trial are then used as one of the pieces of information to decide rationally when and on whom to reduce intraocular pressure medically.

[Timolol eyedrops in ophthalmological practice]

Fifty-eight glaucoma patients (105 eyes) of an ophthalmological practice were treated with Timolol eyedrops (0.1%-0.5% once or twice daily) over a long-term period. In group 1 - without pre-treatment (12 patients) pressure was lowered by 34%. In group II, glaucoma patients who were insufficiently stabilized by conservative treatment. Timolol was added to the glaucoma medication and thus a further pressure decrease of 27% was achieved. Group III comprised 24 glaucoma patients who, although their intraocular pressure was satisfactorily controlled, had problems with their medication. After having been switched to Timolol alone they presented a further decrease in IOP of 22%. Group IV comprised those patients resistant to Timolol therapy (six patients; 10%) who showed no further reduction in IOP--neither with Timolol alone nor in combination with other glaucoma medication. Advantages and slight disadvantages of Timolol therapy were discussed. Timolol is the only local glaucoma medication without ascertainable side-effects and thus represents a gain for the therapeutic spectrum of the practitioner.

The long-term hypotensive effect of timolol maleate compared with the effect of pilocarpine in simple and capsular glaucoma

The long-term intraocular pressure (IOP) lowering effect of a beta-adrenergic blocking agent, timolol maleate, in topical administration was compared with the effect of pilocarpine on simple and capsular glaucoma by means of diurnal pressure curves during a six-month follow-up. In simple glaucoma timolol was more effective than pilocarpine in lowering IOP. In the follow-up a significant but not marked increase of the IOP was observed. In capsular glaucoma timolol was not effective enough, but when it was co-administered with miotics the IOP lowering effect was better than with either substance alone. Timolol induced no accomodative myopia, miosis, reduction of tear flow or other side effects. It increased the outflow facility in simple glaucoma but not in capsular glaucoma. During the trial, the anterior chamber depth increased while the corneal thickness remained unchanged. Four out of the six eyes included in a previous report of secondary glaucoma due to chronic uveitis are still, after one year of therapy, controlled with timolol.

Thymoxamine and intraocular pressure

Topical treatment with 1% thymoxamine produces in rabbit and human eyes a small but real miotic and tension-lowering effect. The latter is more evident using two different models of experimental ocular hypertension in rabbits. In human open-angle glaucoma eyes, tonographic measurements indicate that the outflow facility is left unchanged by the drug.

Ultrasonographic study of the effect of different miotics on the eye components

The effect of topical instillations of carbachol 3%, pilocarpine 2%, aceclidine 2%, aceclidine 2%-adrenaline 1%, and of the Ocusert delivery system was determined and compared in 151 eyes. The depth of the anterior chamber, the thickness and the position of the lens, the length of the vitreous and the refraction were studied. Aceclidine has negligible side effects on the ocular components (maximal change of the anterior chamber 0.20 mm; maximal change of the lens thickness 0.14 mm; maximal myopisation: -1.5 delta. Carbachol has the strongest side effects (maximal change of the anterior chamber 0.80 mm; maximal change of the lens thickness 0.80 mm; maximal myopisation -11.50 delta). Carbachol and pilocarpine may cause an important forward displacement of the lens with the risk of an angle-closure glaucoma in an eye with shallow anterior chamber.

Comparative pharmacologic effects of pilocarpine administered to normal subjects by eyedrops or by ocular therapeutic systems

Normal volunteers used 1, 2, and 4% pilocarpine eyedrops, three times daily, or ocular therapeutic systems placed in the conjunctival cul-de-sac to control intraocular pressure. The systems continuously release 20 and 40 mug/hour of pilocarpine for one week. Although the amount of drug delivered to the eye from the ocular therapeutic system was one fifth that obtained from the eyedrops, the decrease of intraocular pressure was comparable. The ocular therapeutic systems produced small, constant effects on visual acuity, refractive error, and miosis that did not cause visual handicaps or require correction. The effects of eyedrops on these visual factors were large and varied and produced marked visual handicaps that were not correctable with spectacles. Despite its comparable hypotensive effect in normal subjects, continuous delivery of pilocarpine by means of an ocular therapeutic system elicits less severe side effects than pilocarpine eyedrops.