Jens CEULEMANS*, Annick LUDWIG*,o
*Laboratory Pharmaceutical Technology & Biopharmacy Universiteitsplein 1, 2610 Antwerp, BELGIUM.
°Corresponding author

Summary:
Continuous secretion of tears, frequent blinking and a surface epithelium with low permeability are the main factors protecting the eye against external factors. Obviously, this protective barrier also reduces the efficacy of ocular drugs applied topically. The use of mucoadhesive dosage forms can be employed to increase the bioavailability of ocular drugs.
The suitability of polymer preparations (both liquid and solid dosage forms) to lengthen the precorneal residence time of the drug and to achieve an increase of the ocular bioavailability, by means of a mucoadhesive interaction, is evaluated. The clarification of the mucoadhesive interaction mechanism(s) is accomplished by the development of an in vitro technique using oscillatory shear rheology. Implementation of several rheological procedures enables the characterization of the degree and type of network formation between the polymer dispersion and mucin. The results obtained with the in vitro technique are verified in vivo by ocular fluorophotometry determining the ocular elimination kinetics. To influence significantly the precorneal residence time and the ocular bioavailability, the use ofa mucoadhesive minitablets seems to be inevitable. Liquid polymer dispersions can also interact with mucin, but the interaction mechanisms as demonstrated by the in vitro experiments are insufficient to achieve a significant in vivo effect.