Ocular solutions

In addition, liposomes are subject to the same rapid precorneal clearance as conventional ocular solutions, especially the ones with a negative or no surface charge [127], Positively charged liposomes, on the other hand, were reported to exhibit a prolonged precorneal retention due to electrostatic interactions with the negative sialic acid residues of the mucin layer [2,127,208,210-213],... 

Two methods are commonly used to instill topical ocular solutions ... 

Figure 3-3 Traditional technique for instillation of topical ocular solutions.The patient s head is inclined backward, the lower Ud is retracted, the globe is elevated, and the dropper tip is kept at least 2 cm from the globe.

Box 3-1 Recommended Procedure for Instilling Topical Ocular Solutions... 

Topical Marked circulation impairment do not instill ocular solutions when topical corticosteroids are being used on eyelids or surrounding tissues. 

Norfloxacin is a fluoroquinolone that interferes with microbial DNA synthesis. It is indicated as an oral treatment of urinary tract infections (UTIs) caused by susceptible organisms treatment of sexually transmitted diseases (STDs) caused by Neisseria gonorrhoeae ocular solution for treatment of superficial ocular infections due to strains of susceptible organisms and prostatitis caused by E. coli. 

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). 

You can perform (jiiatiLum m cell an ical calculations on a part of a rn o I ocular system, such as a solute, vh ilc using rn o I ocular mcch an -ics for Lh c rest of th o system, such as the solvon t siirroiindin g th o solute. I h is boun dary tech n itjue is avaliable in HyperCbom for all quantum mechanical methods. It is somewhat loss com ploto with ah initio calculations than with som i-cmpirical calculations, however, With ah nii/jo calculation s the boundary must occur between molecules rather than in side a molecule. 

Tests have shown that citric acid is not corrosive to skin but is a skin and ocular irritant (50). Eor these reasons it is recommended that individuals use appropriate personal protection to cover the hands, skin, eyes, nose, and mouth when in direct contact with citric acid solutions or powders. 

Figures 2 and 3 illustrate the constant release of pilocarpiae over the seven day treatment period. An initial burst of dmg iato the eye is seen ia the first few hours. This is temporary and the system drops to the rated value ia approximately six hours. The total amount of dmg released ia this transitory period is less than that normally given ia pilocarpiae ophthalmic solutions. The ocular hypotensive effect of these devices is hiUy developed within 2 hours of placement ia the conjunctival sac, and the hypotensive response is maintained throughout the therapy. This system replaces the need for eyedrops apphed four times per day to control iatraocular pressure.

GLAUCOMA When a cholinergic drug is used to treat glaucoma, die nurse checks the eye and die area around die eye daily for evidence of redness, inflammation, and excessive secretions, particularly if die ocular system is used. If secretions are present around die eye, the nurse removes them with a cotton ball or gauze soaked in normal saline or other cleansing solution recommended by die primary health care provider. 

Water-soluble polymers can also be used as aqueous solutions for drug delivery. Although the polymer is already dissolved, its increase in viscosity of the drug solution causes the drug to be retained somewhat longer in the desired application. This technique is common with ocular, nasal, and oral applications of drug solutions. 

As mentioned previously (and discussed in detail in Sec. IX), contact lens products have specific guidelines that focus on compatibility with the contact lens and biocompatibility with the cornea and conjunctiva [75], These solutions are viewed as new medical devices and require testing with the contact lenses with which they are to be used. Tests include a 21-day ocular study in rabbits and employ the appropriate types of contact lenses with which they are to be used and may include the other solutions that might be used with the lens. Additional tests to evaluate cytotoxicity potential, acute toxicity, sensitization potential (allergenicity), and risks specific to the preparation are also required [75-77], These tests are sufficient to meet requirements in the majority of countries, though testing requirements for Japan are currently much more extensive. 

Some strains of P. aeruginosa are resistant to benzalkonium chloride and, in fact, can be grown in solutions concentrated in this agent. This has caused great concern because of the virulent nature of this organism in ocular infections, as discussed previously. Thus, it was an important finding in 1958 that the acquired resistance could be eliminated by the presence of ethylenediaminetetracetic acid (sodium edetate) in the formulation. This action of EDTA has been correlated with its ability to chelate divalent cations, and it is commonly used as a preservative aid [125]. The use of disodium EDTA, where compatible, is recommended in concentrations up to 0.1%. 

This preservative is comparatively new to ophthalmic preparations and is a polymeric quaternary ammonium germicide. Its advantage over other quaternary ammonium seems to be its inability to penetrate ocular tissues, especially the cornea. It has been used at concentrations of 0.001-0.01% in contact lens solutions as well as dry eye products. At clinically effective levels of preservative, POLYQUAD is approximately 10 times less toxic than benzalkonium chloride [87,137], Various in vitro tests and in vivo evaluations substantiate the safety of this compound [137,141,142], This preservative has been extremely useful for soft contact lens solutions because it has the least propensity to adsorb onto or absorb into these lenses, and it has a practically nonexistent potential for sensitization. Its ad-sorption/absorption with high water and high ionic lenses can be resolved by carefully balancing formulation components [143],... 

Surfactants. The use of surfactants is greatly restricted in formulating ophthalmic solutions. The order of surfactant toxicity is anionic > cationic >> nonionic. Several nonionic surfactants are used in relatively low concentrations to aid in dispersing steroids in suspensions and to achieve or to improve solution clarity. Those principally used are the sorbitan ether esters of oleic acid (Polysorbate or Tween 20 and 80), polymers of oxyethylated octyl phenol (Tyloxapol), and polyoxyl 40 stearate. The lowest concentration possible is used to perform the desired function. Their effect on preservative efficacy and their possible binding by macromolecules must be taken into account, as well as their effect on ocular irritation. The use of surfactants as cosolvents for an ophthalmic solution of chloramphenicol has been described [271]. This com-... 

The anhydrous petrolatum base may be made more miscible with water through the use of an anhydrous liquid lanolin derivative. Drugs can be incorporated into such a base in aqueous solution if desired. Poly-oxyl 40 stearate and polyethylene glycol 300 are used in an anti-infective ointment to solubilize the active principle in the base so that the ointment can be sterilized by aseptic filtration. The cosmetic-type bases, such as the oil-in-water (o/w) emulsion bases popular in dermatology, should not be used in the eye, nor should liquid emulsions, owing to the ocular irritation produced by the soaps and surfactants used to form the emulsion. 

An erodible insert developed as a potential ocular drug-delivery system is marketed as a prescription drug for the lubricant properties of the polymer base. Lacrisert is a sterile ophthalmic insert used in the treatment of moderate to severe dry eye syndrome and is usually recommended for patients unable to obtain symptomatic relief with artificial tear solutions. The insert is composed of 5 mg of hydroxypropylcellulose in a rod-shaped form about 1.27 mm diameter by about 3.5 mm long. No preservative is used, since it is essentially anhydrous. The quite rigid cellulose rod is placed in the lower conjunctival sac and first imbibes water from the tears and after several hours forms a... 

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