We have located links that may give you full text access.
Investigation of Ocular Bioactivation Potential and the Role of Cytochrome P450 2D Enzymes in Rat.
BACKGROUND: Timolol is clinically administered topically (ocular) to reduce intraocular pressure and treat open-angle glaucoma. Ocular administration of timolol in low doses (0.5% w/v in the form of eye drops) has led to challenges for in vivo metabolite identification. An understanding of drug metabolism in the eye is important for clinical ocular therapeutics and potential drug candidates.
METHODS: We aimed to investigate the metabolism of timolol in rat ocular and liver S9 fractions, as well as rat ocular tissue and plasma following a 0.5% topical (ocular) dose of timolol. We explored the potential in vitro metabolic bioactivation in the eye/liver by conducting trapping studies for putative aldehyde and iminium ion intermediates that may arise from the morpholine functionality.
RESULTS: Oxidative metabolism of timolol to its major metabolite (M4) in ocular S9 and recombinant rat cytochrome P450 (CYP) isoforms supports the possible role of rat ocular CYP2D2, 2D4, and/or 2D18. Observation of N-acetyl-timolol (M5) is suggestive that the ocular N-acetyltransferases may also play a larger role in ocular disposition of timolol, a previously unreported finding. This research is the first comprehensive report of in vitro ocular metabolism of timolol in rat.
CONCLUSION: This study also indicates that in vitro hepatic metabolism is over-predictive of ocular metabolism following topically ocular dosed timolol. The research, herein, highlights the eye as an organ capable of first pass metabolism for topical drugs. Thus, new ophthalmologic considerations for studying and designing long term topical therapies in preclinical species are needed in drug discovery.
METHODS: We aimed to investigate the metabolism of timolol in rat ocular and liver S9 fractions, as well as rat ocular tissue and plasma following a 0.5% topical (ocular) dose of timolol. We explored the potential in vitro metabolic bioactivation in the eye/liver by conducting trapping studies for putative aldehyde and iminium ion intermediates that may arise from the morpholine functionality.
RESULTS: Oxidative metabolism of timolol to its major metabolite (M4) in ocular S9 and recombinant rat cytochrome P450 (CYP) isoforms supports the possible role of rat ocular CYP2D2, 2D4, and/or 2D18. Observation of N-acetyl-timolol (M5) is suggestive that the ocular N-acetyltransferases may also play a larger role in ocular disposition of timolol, a previously unreported finding. This research is the first comprehensive report of in vitro ocular metabolism of timolol in rat.
CONCLUSION: This study also indicates that in vitro hepatic metabolism is over-predictive of ocular metabolism following topically ocular dosed timolol. The research, herein, highlights the eye as an organ capable of first pass metabolism for topical drugs. Thus, new ophthalmologic considerations for studying and designing long term topical therapies in preclinical species are needed in drug discovery.
Full text links
Related Resources
Trending Papers
Challenges in Septic Shock: From New Hemodynamics to Blood Purification Therapies.Journal of Personalized Medicine 2024 Februrary 4
Molecular Targets of Novel Therapeutics for Diabetic Kidney Disease: A New Era of Nephroprotection.International Journal of Molecular Sciences 2024 April 4
Perioperative echocardiographic strain analysis: what anesthesiologists should know.Canadian Journal of Anaesthesia 2024 April 11
The 'Ten Commandments' for the 2023 European Society of Cardiology guidelines for the management of endocarditis.European Heart Journal 2024 April 18
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app