Controlled drug delivery devices for experimental ocular studies with timolol 2. Ocular and systemic absorption in rabbits

Arto Urtti, James D. Pipkin, Gerald Rork, Toshiaki Sendo, Ulla Finne, A. J. Repta

Research output: Contribution to journalArticlepeer-review

83 Citations (Scopus)

Abstract

Controlled drug delivery was tested as a means to decrease the potentially dangerous systemic drug concentrations which are associated with timolol eyedrop therapy. l-Tumolol (125 μg) was administered in 0.5% eyedrops (25 μl, pH 6.86) and in controlled release silicone tubing devices (dose 57.6 μ;g; release rate 7.2 μg h for 8 h) in the eyes of pigmented rabbits. [3H]Timolol tracer was used in ocular absorption studies and unlabeled timolol dosage forms in systemic absorption studies. [3H]Timolol concentrations were determined in ocular tissues and tear fluid. Beta blocking activity in plasma was determined using a radioreceptor assay. Comparable timolol concentrations were achieved in the iris-ciliary body with silicone tubing devices (57.6 μg) and with eyedrops (125 μg). The relative ocular timolol bioavailability after controlled drug delivery was about 2-fold greater than from eyedrops. In plasma, peak beta-blocking activity was much higher after eyedrop administration (17.16 ± 2.40 ng/ml) than during controlled timolol delivery (< 1.0 ng ml). The results indicate that controlled drug delivery is a viable alternative in improving the therapeutic index of glaucoma therapy with timolol.

Original languageEnglish
Pages (from-to)241-249
Number of pages9
JournalInternational Journal of Pharmaceutics
Volume61
Issue number3
DOIs
Publication statusPublished - Jun 30 1990
Externally publishedYes

Keywords

  • Controlled drug release
  • Ocular absorption
  • Ocular drug delivery
  • Pharmacokinetics
  • Radioreceptor assay
  • Silicone tubing
  • Systemic absorption
  • Timolol

ASJC Scopus subject areas

  • Pharmaceutical Science

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