Influence of the vasodilator drug isosorbide dinitrate on ocular circulation

Background Vasodilator drugs are increasingly being discussed as possible antiglaucomatous substances. Aim of the present study is to evaluate, from a hemodynamic point of view, the vasodilator drug isosorbide dinitrate (ISDN) regarding its suitability for glaucoma therapy. Methods 20 healthy subjects (mean age: 28 yrs) volunteered to participate in the study. In randomized order, each subject received one tablet containing 40 mg ISDN (sequels) or - in a second trial - one tablet placebo (+ 500 mg of the analgetic metamizol, respectively, for prophylaxis of nitrate headache). 1 h before as well as 1, 3? 5, and 7 hrs after medication, the following variables were determined using oculo-oscillo-dynamography: systolic ophthalmic artery pressure (SOAP), systolic ocular perfusion pressure (SOPP), ocular pulsation amplitude (OPA) and the product OPA x heart rate (HR). Intraocular pressure (IOP) as well as systolic and diastolic brachial artery pressures (SBAP, DBAP) were also measured. Results After administration of ISDN (+ analgetic), the variables SBAP, SOAP and SOPP were significantly (p = 0,01) towered compared to placebo ( + analgetic), and also the IOP tended to be lower (p = 0.08). The maximum reduction was found 3-5 hrs after medication: SBAP 10.9 mm Hg (9%), SOAP 12.5 mm Hg (14%), SOPP 11.3 mm Hg (14.5%), and IOP 1.5 mm Hg (12%). The relation SOAP vs. SBAP was significantly (p = 0.0004) linear, the correlation coefficient amounted to 0.39, DBAP remained unchanged, KR was increased by 4-7 beats/min (p = 0.08). OPA and the product OF-A x HR showed highly significant decreases by maximum values of 44% and 40%, respectively. Conclusions ISDN (+ analgetic) caused a reduction of SOAP and SOPP, which can be accounted for by the reduced systolic systemic blood pressure. In addition, there was a decrease of OPA and of the product OPA x HR (a measure of pulsatile ocular blood flow), which finding may be explained by a cardiac strobe volume reduction that is typical for nitrates. Due to these hemodynamic effects and due to the only weak IOP reduction, ISDN does not appear to be suitable for glaucoma therapy.