Osmotic Drugs

PETER A. NETLAND and ALLAN E. KOLKER

Osmotically active ocular hypotensive agents were initially tried early in the twentieth century, when Andre Cantonnet described the oral use of sodium chloride and lactose for lowering intraocular pressure (IOP).1 In 1914, Emil Hertel influenced IOP by intravenous injection of anisotonic solutions.2 Many of these agents, such as concentrated saline, sodium carbonate, sugars, and gum acacia, while producing adequate ocular responses, did not stand the test of time because of their untoward side effects and the inadequate duration of their osmotic effect. After the ocular hypotensive effect of intravenous urea was described in 1958 and was further studied in glaucoma patients,3,4 this drug became the first hyperosmotic agent to achieve widespread use in glaucoma therapy.

The use of urea has been superseded by other osmotic drugs in current ophthalmic clinical practice (figure 8.1). Orally administered mannitol is poorly absorbed from the gastrointestinal tract; however, in 1962, intravenous mannitol was shown to lower IOP.5,6 Glycerol, introduced in 1963 by Virno et al.,7 was the first practical oral osmotic drug for the reduction of IOP. In 1967, Becker, Kolker, and Krupin8 described the use of oral isosorbide as preoperative medication and as therapy for patients with acute glaucomas.

Although osmotic agents for reduction of IOP are infrequently used, they may be more effective than other glaucoma medications in the short-term treatment of certain types of glaucomas. Osmotic drugs are useful in the preoperative preparation of select patients for intraocular surgery. These drugs are also effective in the initial treatment of acute and extreme elevation of IOP, including angle-closure glaucoma and certain secondary glaucomas.

Figure 8.1. Osmotic drugs.

Figure 8.1. Osmotic drugs.

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