Info

Pilagan

1%, 2%, 4%

qid

Pilofrin

0.5% (+0.12% phenylephrine HCl)

qid

aIf available in the United States, then only those brands are listed.

bNot used in the United States.

aIf available in the United States, then only those brands are listed.

bNot used in the United States.

cTwice-daily application may suffice for light eyes.

Source: Red Book. Thomson Micromedix Healthcare Series. Greenwood Village, CO: Thomson Micromedix; 2006.

may occur but are unusual. Recent evidence suggests that prolonged use of topical glaucoma drug therapy, including pilocarpine, may increase inflammatory cells in the conjunctival tissues, making subsequent glaucoma filtration surgery more likely to fail.31,32 Intraocular vascular congestion may occur in, and aggravate, uveitic conditions. Following long-term use of the strongest indirect-acting cholinomi-metics, dilation of blood vessels and resulting greater permeability can increase postoperative inflammation ad may increase the risk of hyphema during ophthalmic surgery.33 Ciliary spasm, temporal or supraorbital headache, and induced myopia may occur, all consequent to drug-induced contraction of the ciliary muscle; this is most common in young, prepresbyopic patients. Reduced visual acuity in poor illumination is frequently experienced by older individuals and those with lens opacities, consequent to miosis reducing the amount of light reaching the retina through an already partly opaque lens. Young individuals with clear lenses are rarely bothered by the miosis. A few cases of retinal detachment have been attributed to pilocarpine in certain susceptible individuals. Some evidence suggests that long-term use of pilocarpine may accelerate the development of lens opacities, but this is not proven conclusively. Intense miosis and cyclotonia produced at the higher doses may, respectively, increase pupillary block or induce ciliary block sufficiently to induce angle-closure glaucoma in susceptible individuals.

The primate ciliary muscle is structurally unique, exhibiting three distinct morphologic regions: an outer, longitudinal portion; an inner, apical circular portion; and an intermediate, obliquely oriented reticular region. The appearance, relative sagittal section area, and topographic interrelationship of the three regions differ in the relaxed versus cholinergic-agonist-contracted muscle (figure 5.5).34 Histo-chemical and ultrastructural differences exist between different regions of the ciliary muscle,35 more than one subtype of muscarinic receptor may be present, and the receptor subtypes may differ between regions.36-39 In monkeys, topical or intra-cameral pilocarpine induces a greater facility response per diopter of accommodation than does systemic pilocarpine,40 and in humans topical pilocarpine increases facility more per diopter of accommodation than does voluntary near focus.41 This finding suggests selective cholinomimetic stimulation of receptor subtypes may permit separation of desirable and undesirable ocular side effects. However, in monkeys, one subtype (the M3 subtype) appears to modulate the outflow facility and the accommodative and miotic responses to pilocarpine and aceclidine. The concentrations of these agonists required to produce an effective outflow facility response also induce miosis.42,43 More recently, a muscarinic agonist with no activity at the M3 subtype was able to lower IOP in a monkey glaucoma model.44

Some glaucoma patients become refractory to the IOP-lowering effects of pilo-carpine during long-term therapy, even when successively higher doses are given. The mechanism underlying this phenomenon is unclear. It could be consequent to worsening of the outflow disease or to desensitization. Responsiveness to cholinergic drugs may be mediated in part by muscarinic receptor content of the smooth muscle (figure 5.6).45-49 Topical treatment of the monkey eye with echothiophate drops, sustained-release pilocarpine delivery systems, or a single dose of carbachol under a contact lens causes decreased responsiveness to cholinergic agonists in the accommodative and aqueous outflow mechanisms, attributed to agonist-induced cholinergic

Figure 5.5. Results of morphometric analysis of ciliary muscle of vervet monkeys during relaxation (A) and during moderate (B) and strong (C) contraction induced by pilocarpine: area of longitudinal (dark orange), reticular (light orange), reticular plus circular (yellow), and purely circular (green) muscle portions as percentages of the entire muscle area. Modified with permission from figures 4 and 5 (pp. 127 and 128) of Lütjen E. Histometrische Untersuchungen über den Ziliarmuskel der Primaten. [Histometric studies on the ciliary muscle in primates.] Graefes Arch Klin Exp Ophthalmol. 1966;171:121-133. Copyright 1966 Springer-Verlag GmbH & Co KG.

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