Influence of the Vasodilator Drug Isosorbide Dinitrate on Ocular Circulation

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Abstract
Objective: To evaluate the ocular hemodynamic effects of the vasodilator drug isosorbide dinitrate. Design: Randomized, prospective, controlled clinical trial assessing the short-term effects of 1 tablet containing 40 mg of isosorbide dinitrate vs placebo. Setting: Department of Ophthalmology, University of Giessen, Germany. Main Outcome Measures: Systolic ophthalmic artery pressure (SOAP), systolic ocular perfusion pressure (SOPP), ocular pulsation amplitude (OPA), product of OPA × heart rate (HR), intraocular pressure (IOP), systolic and diastolic brachial artery pressure (SBAP and DBAP). Measurements were performed before and up to 7 hours after patients received the medication. Participants: Twenty healthy subjects (mean age, 28 years) who provided informed consent. Results: After isosorbide dinitrate administration, SBAP, SOAP, and SOPP were significantly lowered (P=.01), and IOP tended to be lower (P=.08) compared with placebo. Maximum reduction was 3 to 5 hours after medication: SBAP was reduced by 10.9 mm Hg (9% reduction; P=.01), SOAP was reduced by 12.5 mm Hg (14% reduction; P=.01), SOPP was reduced by 11.3 mm Hg (14.5% reduction; P=.01), and IOP by 1.5 mm Hg (12% reduction; P=.08). The relation between SBAP and SOAP was significantly linear (P<.001), the correlation coefficient was 0.39. The DBAP remained unchanged, and the HR increased by 4 to 7/min (P=.08). The OPA and the product OPA×HR were significantly decreased (P<.001;P=.002) by maximum values of 44% and 40%, respectively. Conclusions: Administration of isosorbide dinitrate reduced SOAP and SOPP, reflecting reduced systemic systolic blood pressure. The decrease in OPA and the product OPA×HR (a measure of pulsatile ocular blood flow) may reflect a reduction in cardiac stroke volume typical for nitrates. Due to these hemodynamic effects and the minute reduction in IOP, the vasodilator drug isosorbide dinitrate, which has been proposed for glaucoma therapy, may be used only with caution in patients with glaucoma.

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