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Related Experiment Videos

Application site dependent ocular absorption of timolol.

A Urtti1, T Sendo, J D Pipkin

  • 1Department of Pharmaceutical Chemistry, University of Kansas, Lawrence.

Journal of Ocular Pharmacology
|January 1, 1988
PubMed
Summary

Topical ocular timolol absorption varies by application site. Silicone devices show higher absorption when placed in the superior conjunctival sac, improving ocular drug delivery.

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Area of Science:

  • Ophthalmology
  • Pharmacokinetics
  • Drug Delivery Systems

Background:

  • Topical ocular drug delivery faces challenges in achieving uniform drug distribution.
  • Timolol is a widely used beta-blocker for glaucoma treatment.
  • Controlled-release systems aim to improve ocular drug bioavailability.

Purpose of the Study:

  • To investigate the ocular absorption and distribution of timolol from silicone devices in rabbits.
  • To compare ocular absorption of timolol administered via eyedrops versus controlled-release devices.
  • To evaluate the effect of device placement (inferior vs. superior conjunctival sac) on timolol distribution.

Main Methods:

  • Topical ocular administration of 3H-timolol in rabbits using eyedrops and silicone cylindrical devices.
  • Devices released timolol at a controlled rate (7.2 micrograms/h).
  • Analysis of timolol concentrations in various ocular tissues (cornea, conjunctiva, sclera, iris-ciliary body, aqueous humor) based on application site.

Main Results:

  • Timolol distribution was uniform with eyedrop administration.
  • Device application resulted in site-dependent, unequal timolol distribution in ocular tissues.
  • Superior conjunctival sac placement led to increased corneal and overall ocular absorption compared to inferior placement.
  • Low aqueous humor concentrations suggested significant noncorneal absorption from the inferior sac.

Conclusions:

  • The application site of controlled-release timolol devices significantly impacts ocular absorption and distribution.
  • Superior conjunctival sac placement enhances timolol bioavailability.
  • Controlled release does not guarantee uniform distribution within the preocular tear fluid.

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