Miotics, in glaucoma

Indications Miotic in glaucoma treatment, reverses toxic CNS... 

Very potent miotic in glaucoma somewhat stable in water... 

Antiglaucoma Preparations and Miotics Sympathomimetics in glaucoma therapy (clonidine, brimonidine)... 

When used for routine mydriasis, hydroxyamphetamine appears to be effective while causing Uttle, if any, ocular irritation. It has been suggested that, due to the indirect action of this drug, it may be a safe mydriatic to use in eyes with shallow anterior chambers, and it may be more readily counteracted with miotics. In patients with open-angle glaucoma, hydroxyamphetamine elevates lOP minimally, if at all. Reductions of lOP have also been reported. 

It is used chiefly as a miotic. The eonstrietion of pupil commences within 10 minutes of application and the effect lasts up to 12 hours. It is also employed to decrease intra-ocular pressure in glaucoma. The salieylate is eomparatively less deliqueseent than the sulphate. The drug is invariably recommended for marginal comeal ulcers. It also finds its seldom use for atony of the urinary bladder. 

Axcisson. U. (1969). Glaucoma, miotic therapy and cataract. V. Studies on the lens in glaucoma eyes after discontinuance of ccothiophate pho.spholinc iodide therapy. Acta Ophthalmol. 47, 1049-1046. 

CiiHi NjOa, Mr 208.26, oily liquid or crystals, mp. 34 °C (as hydrochloride 193-205 °C, nitrate I74°C), bp. 260°C (0.7 kPa), [a] > +106° (HjO), soluble in water, ethanol, chloroform forms well crystallizing salts with acids. P. is the main alkaloid of the South American jaborandi tree (Pilocarpus jaborandi). It is isolated from the leaves. P. is also easily accessible by synthesis and is used as its salts in medicine as a cholinergic parasympathicomimetic, miotic (for glaucoma) agent and as an atropine antagonist it is also used in veterinary medicine for colics and constipation. Detection by means of Helch s reaction. Pilocarpus species contain further imidazole alkaloids (see table). 

Glaucoma Management of open-angle (chronic simple) glaucoma may be used in combination with miotics, beta blockers, hyperosmotic agents, or carbonic anhydrase inhibitors. 

The antimuscarinic properties result in what are usually the most troublesome adverse effects dry mouth, blurred vision, constipation, and (mainly in older males) urinary hesitancy and retention. Pupil size, and hence risk of glaucoma, is determined by a balance between anticholinergic (mydriatic) and sympathomimetic (miotic) effects. 

Glaucoma therapy with strong miotic agents in myopic eyes... 

The drug can also be used concomitantly with echo-thiophate to prevent the formation of miotic cysts during treatment of open-angle glaucoma or accommodative esotropia. Addition of the 2.5% concentration to the echothiophate regimen is recommended. The mechanism whereby phenylephrine prevents cyst formation is not known. However, inhibition of the intense miosis may account, at least in part, for the beneficial effect. 

Since its introduction into clinical practice in 1876, pilocarpine has remained the most usefiil miotic for management of primary open-angle glaucoma, acute angle-closure glaucoma, and many secondary glaucomas. Pilocarpine is commercially arailable as an ophthalmic solution in concentrations from 0.25% to 10% (see Table 10-7). Pilocarpine is also commercially available as a 4% ophthalmic gel that is supplied in 3 5-g tubes. 

Pilocarpine therapy should be avoided in certain patients (Box 10-10).This drug is contraindicated in patients with cataract, especially nuclear sclerotic and posterior subcapsular cataract, because the drug can affect vision and may accelerate the formation of lens opacities. Pilocarpine is generally contraindicated in patients younger than 40 years of age because of the intolerable accommodative spasm and refractive changes. Because breakdown of the blood-aqueous barrier occurs with the use of pilocarpine and other miotics, particularly in the presence of neovascular and uveitic glaucoma, pilocarpine should be avoided in these patients. 

In most cases the treatment of these conditions involves both anti-inflammatory (typically topical corticosteroids) and antiglaucoma (typically aqueous suppressants) medications. Cycloplegics are used to prevent or manage posterior synechia, secondary neovascular glaucoma, and choroidal effusion. Miotics are typically avoided in the management of these conditions because their use... 

Eyes with potential angle closure require a miotic drug and should not be treated with beta-blockers alone. To exclude the risk of precipitating glaucoma in a susceptible individual, gonioscopy is recommended before starting topical beta-adrenoceptor antagonist therapy. 

Pilocarpine-induced miosis has very little value in managing glaucoma in the horse and may increase lOP (van der Woerdt et al 1998). Miotics may also potentiate the clinical signs of uveitis where these are present. 

Pilocarpine is widely used as a topical miotic for controlling the elevated intraocular pressure associated with glaucoma. Beside its low lipophilicity, which stimulated the search for prodrugs,pilocarpine has a short duration of action, its lactonic ring being rapidly opened to yield pilo-carpic acid. In pilocarpine, by substituting the lactonic ester function by its carbamate equivalent, a much more stable analog, which is as effective as pilocarpine, was obtained. ... 

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