Key result
In rabbits, D-timolol and domperidone increased retinal blood flow by 9% and 12%, respectively, whereas L-timolol and haloperidol reduced it by 17% and 16%.
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Preclinical rabbit data should not alter timolol prescribing; leaves open stereospecific retinal flow modulation for targeted human studies.
L-Timolol (0.4 mg/kg) reduced significantly retinal blood flow (17%), systemic blood pressure (18-20%) and heart rate (28%) in the rabbit. D-Timolol (4.0 mg/kg) increased retinal blood flow slightly (9%) and did not significantly affect systemic blood pressure or heart rate. Since D-timolol is effective in reducing intraocular pressure, these results indicate that D-timolol is superior to L-timolol for glaucoma treatment. Haloperidol and domperidone are dopamine antagonists, but, while haloperidol (0.1 mg/kg) suppressed retinal blood flow (16%), domperidone (0.2 mg/kg) increased it (12%). Neither of them affected blood pressure or heart rate significantly. While either of these given topically decreases intraocular pressure significantly, domperidone's ability to increase retinal blood flow makes it more useful than either haloperidol or L-timolol for treating glaucoma.
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Yan et al. (2009) studied Glaucoma. L-Timolol, D-Timolol, Haloperidol, and Domperidone was evaluated on Retinal blood flow. In rabbits, D-timolol and domperidone increased retinal blood flow by 9% and 12%, respectively, whereas L-timolol and haloperidol reduced it by 17% and 16%.
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