Лако-красочные материалы — производство

Drug delivery to the eyes is made difficult by dilution of drug in the tears and the natural mechanisms of blinking and high tear turnover rate, which protect the eye from external contaminants. Traditional aqueous, ocular delivery systems are administered dropwise, and due to the foregoing conditions, bioavailability is severely limited for either local or systemic therapy. Although many attempts have been made to prolong drug release of ocular delivery systems, few have proven to be completely successful when patient accep­tance, drug bioavailability, and cost are considered. For a drug to be sustained in the eye, it must be maintained in the precorneal area and deliver drug to this area for an extended period of time. Ocular bioadhesive delivery systems could therefore show a sustained effect if they penetrate the aqueous tear film and interact with the underlying mucin or cell layer. If firmly attached to the surface, the dosage form could remain in the preocular area longer than conventional ocular dosage forms, and if dissolution of drug release is controlled, utilization of water-soluble drug can be increased significantly.

Pilocarpine is a drug commonly used in glaucoma therapy to relieve intraocular pressure (IOP), which is a cause of great discomfort to the patient. Piloplex is a sus­tained-release product based on an emulsion system of pilocarpine bound to a polymeric carrier [87,88]. Piloplex was shown to prolong a reduction in IOP as compared to standard pilocarpine hydrochloride drops. This is attributed to its bioadhesive properties, which keep the drug in the precorneal area longer than do conventional ocular dosage forms.

The release of progesterone used as a model drug in an ocular delivery system consisting of cross-linked acrylic acid has been shown to be sustained [89]. The delivery system showed increased bioavailability 4.2 times greater than a suspension without poly­mer and showed excellent bioadhesion to the conjunctinal mucosa of the albino rabbit. Another system utilizing polycarbophil also showed increased bioavailability of a fluor — ometholone steroid suspension used for the treatment of inflammation [90]. Aqueous humor drug levels were maintained above the therapeutic minimum for 8 h in albino rabbits, and the mean residence time of fluorometholone was increased 1.7 times over an aqueous suspension.