Ophthalmic therapeutics solutions

Solutions The two major physical forms of eyedrops are aqueous solutions and suspensions. Nearly all the major ophthalmic therapeutic agents are water soluble or... 

Although tyrothricia is too toxic for parenteral therapy, it was formerly sold in the United States as oral lo2enges. Modem tyrothricin formulations are composed of 70—80% tyrocidines and 30—20% linear gramicidins. Tyrocidines are not as active as linear gramicidins and are too toxic for any therapeutic use by themselves. The bactericidal linear gramicidins are used in the United States solely as an ophthalmic solution in combination with polymyxin B sulfate and neomycin sulfate. The linear gramicidin is used in this aqueous product as a substitute for bacitracin, which lacks stabiUty under such conditions. 

The therapeutically inactive ingredients in ophthalmic solution and suspension dosage forms are necessary to perform one or more of the following functions adjust concentration and tonicity, buffer and adjust pH, stabilize the active ingredients against decomposition, increase solubility, impart viscosity, and act as solvent. The use of unnecessary ingredients is to be avoided, and the use of ingredients solely to impart a color, odor, or flavor is prohibited. 

Furthermore, addition of a penetration enhancer to the vehicle of an ophthalmic solution has been used to reduce the size of the drop instilled. Since this reduction in drop size results in a decreased washout and systemic drug loss, this would result in a decreased potential for systemic toxicity, at the same time improving the ocular absorption of poorly absorbed drugs [109], Therefore, improved ocular bioavailability and therapeutic response could be obtained. 

To enhance corneal drug absorption, the tear film concentration can be prolonged by manually blocking the nasolacrimal ducts or by tilting the head back to reduce drainage (see Chapter 3). Another effective technique to increase corneal penetration is to administer a series of ophthalmic solutions at intervals of approximately 10 minutes. It has been determined, however, that when different drug formulations are given as drops in rapid succession, the medications first applied are diluted and do not achieve fiill therapeutic potential. 

Gilbard JP Rossi SR, Heyda KG. Ophthalmic solutions, the ocular surface, and a unique therapeutic artificial tear formulation. AmJ Ophthalmol 1989 107 348-355. 

Studies of the antimicrobial and therapeutic properties of silver and its derivatives have yielded an extensive scientific literature, ranging from clinically- to biochemically-based papers. The latter area includes studies in enzymatic and other macromolecular interactions to silver resistance encompassing plasmid-mediated patterns. The reduction to one silver compound (AgSD) in the current British National Formulary and to two compounds (AgSD and silver nitrate ophthalmic solution) in USP XXII may not be a true reflection of the use of silver in health care today. Silver compounds also find use in non-clinical situations, for example, as water disinfectants and, not considered in this review, as silver staining techniques for microscopy. 

Eye Washes. See Solutions, ophthalmic. Fluidextracts Fluidextracts are concentrated liquid preparations representing the therapeutically active principles of vegetable drugs. They are formulated in such a way that the activity of one gram of the drug is contained in one milliliter of the fluid-extract. They are generally prepared by some form of percolation, using alcohol in the menstruum. Fluid-extracts first became official in 1850 when five were entered in the United States Pharmacopeia by their... 

Chlorobutanol is primarily used in ophthalmic or parenteral dosage forms as an antimicrobial preservative at concentrations up to 0.5% w/v see Section 10. It is commonly used as an antibacterial agent for epinephrine solutions, posterior pituitary extract solutions, and ophthalmic preparations intended for the treatment of miosis. It is especially useful as an antibacterial agent in nonaqueous formulations. Chlorobutanol is also used as a preservative in cosmetics [see Section 16) as a plasticizer for cellulose esters and ethers and has been used therapeutically as a mild sedative and local analgesic. 

Sodium acetate is used as a buffering agent in various intramuscular, intravenous, topical, ophthalmic, nasal, oral, otic, and subcutaneous formulations. It may be used to reduce the bitterness of oral pharmaceuticals. It can be used to enhance the antimicrobial properties of formulations it has been shown to inhibit the growth of S. aureus and E. coli, but not C. albicans in protein hydrolysate solutions. It is widely used in the food industry as a preservative. Sodium acetate has also been used therapeutically for the treatment of metabolic acidosis in premature infants, and in hemodialysis solutions. ... 

While ophthalmic solutions are by far the most preferred dosage forms, ophthalmic ointments are still being marketed for night time applications and where prolonged therapeutic actions are required. 

Frequent instillation of solution or higher drug concentration is needed to achieve the desired therapeutic response. But this attempt is potentially dangerous if drug solution drained from the eye is systemically absorbed from the nasolacrimal duct. To increase precorneal residence time and ocular bioavailability, different ophthalmic delivery systems such as viscous solutions, ointments, gels, suspensions, or polymeric inserts are used. But because of blurred vision (e.g., ointments) or lack of patient compliance (e.g., inserts), these formulations have not been widely accepted. 

Although satisfactory therapeutic results are obtained with usual topical ophthalmic drug (topical ocular solutions and ointments) they present some inconveniences pt. Bioavailability is poor, requiring high doses and repeated applications. 2 . Diffusion of the drug into the bloodstream across de nasal mucosa which is continuous with the conjuntival sac, represents an additional risk of systemic toxicity. (Chang and Lee, 1987, Salminen,1990). 

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