Biomedical subjects

S Dallinger

Publications and source records attributed to S Dallinger.

22 records · Page 2Linked to original sources

PubMed1998

Age dependence of choroidal blood flow.

OBJECTIVE: To investigate the age dependence of choroidal blood flow. DESIGN: A cross-sectional study. SETTING: Department of Clinical Pharmacology, Vienna University. PARTICIPANTS: A total of 130 healthy volunteers between the ages of 19 and 83 years. MEASUREMENTS: Fundus pulsation amplitude (FPA) with a recently developed laser interferometric method, mean arterial pressure (MAP) with an automated oscillometric device, intraocular pressure (IOP) with an applanation tonometer, and ocular perfusion pressure (OPP) as calculated from MAP and IOP. RESULTS: There was a significant correlation of FPA with age r = -0.242 (P = .005). MAP, IOP, and OPP showed a significant positive correlation with age. Multiple regression analysis showed that FPA is associated with age but not with MAP, IOP, or OPP. CONCLUSION: Choroidal blood flow is reduced in older subjects, which argues in favor of an increase in ocular vascular resistance with age. This may be a risk factor in the development of common ocular diseases such as age-related macular degeneration or glaucoma.

Adult↗

PubMed1998

Effects of acetazolamide on choroidal blood flow.

BACKGROUND AND PURPOSE: The acetazolamide provocation test is commonly used to study cerebrovascular vasomotor reactivity. On the basis of the effect of a carbonic anhydrase inhibitor in the central nervous system, we hypothesized that acetazolamide may also increase blood flow in the human choroid. METHODS: In a placebo-controlled, randomized, double-blind, three-way crossover design, acetazolamide (500 mg or 1000 mg i.v.) or placebo was administered to nine healthy subjects. The effect of acetazolamide was studied at 15-minute intervals for 90 minutes. Pulsatile choroidal blood flow was assessed with laser interferometric measurement of fundus pulsation. In addition, mean blood flow velocity and resistive index in the ophthalmic artery were measured with Doppler sonography. In a second study in six healthy subjects, we assessed the effect of acetazolamide (1000 mg i.v.) on intraocular pressure. RESULTS: Acetazolamide increased fundus pulsation amplitude in a dose-dependent manner (1000 mg: +33%; 500 mg: +20%; P<0.001, ANOVA). The effect of acetazolamide on MFV (1000 mg: +18%; 500 mg: +8%; P=0.003, ANOVA) and RI (1000 mg: -4%; 500 mg: -2%; P=0.006, ANOVA) was less pronounced but also significant. Acetazolamide did not induce any changes in systemic hemodynamic parameters but significantly decreased intraocular pressure (1000 mg: -37%; P<0.0001). CONCLUSIONS: The present data show for the first time that intravenously administered acetazolamide increases choroidal blood flow in humans. This phenomenon therefore indicates that the acetazolamide provocation test may qualify as a tool to investigate ocular vasomotor reactivity in a variety of ocular diseases. Moreover, the increase in choroidal blood flow after carbonic anhydrase inhibition can be expected to contribute to the therapeutic efficacy of carbonic anhydrase inhibitors in glaucoma.

Acetazolamide↗

PubMed1998

Noninvasive investigations of the normal ocular circulation in humans.

PURPOSE: To compare the reproducibility of laser interferometric measurements of fundus pulsation, pneumatonometric measurement of pulse amplitude (PA) and pulsatile ocular blood flow (POBF), and Doppler ultrasonic measurements of blood flow velocity in the ophthalmic artery (OA) and the posterior ciliary arteries (PCAs) and to investigate the association of the results obtained with these methods and to characterize ocular hemodynamics during Valsalva maneuver and isometric handgrip. METHODS: All studies were performed in healthy subjects. Fundus pulsation (n = 48), POBF (n = 24), and blood flow velocities (n = 24) were measured at baseline and during the Valsalva maneuver and isometric handgrip. Intraclass correlation coefficients were calculated for test/retest variability, for short-term variability, and for interobserver variability. RESULTS: Intraclass correlation coefficients were between 0.95 and 0.98 for fundus pulsation measurements, between 0.54 and 0.76 for pneumatonometric measurements, between 0.44 and 0.88 for Doppler sonographic measurements in the OA and between 0.32 and 0.60 in the PCAs. There was a high degree of association between pneumatonometric parameters and fundus pulsation amplitude. Valsalva maneuver significantly reduced fundus pulsations, PA, and POBF, whereas isometric handgripping did not change these parameters. CONCLUSIONS: The reproducibility of fundus pulsation measurements was excellent. Reproducibility of pneumatonometric parameters and ultrasonographic measurements in the OA was satisfactory. Reproducibility of ultrasonographic measurements in the PCAs was low. Data obtained during the autonomic stimuli experiments argue against the sole use of systems to measure pulsatile blood flow, if no additional data on flow pulsatility are available. At least in cases when changes in blood pressure are likely to occur the ratio of pulsatile to nonpulsatile blood flow might not be constant and POBF might not be an adequate measure of total ocular blood flow.

Adult↗

PubMedDate not supplied

Pharmacokinetics and pharmacodynamics of the novel H1-receptor antagonist emedastine in healthy volunteers.

OBJECTIVE: Emedastine is a novel H1-receptor antagonist with pre-clinically well-documented anti-allergic effects. Here, we set out to study the relationship between emedastine pharmacokinetics and the suppressive effect on histamine-induced wheals and flares, and to compare these effects to placebo and cetirizine. METHODS: Emedastine (4 mg q.d.), emedastine (2 mg b.i.d.), cetirizine (10 mg q.d.) and placebo were administered to healthy volunteers in a double-blind, cross-over fashion. On day 1 and day 5 (steady state) following drug administration, wheals and flares were induced by skin-prick testing with 1 mg ml(-1) or 10 mg ml(-1) histamine. RESULTS: Following the administration of 4 mg emedastine q.d., mean area under the concentration-time curve (AUC)0-24 values of 34.49 +/- 24.07 ng h ml(-1) and 47.05 +/- 36.12 ng h ml(-1) were attained on day 1 and day 5, respectively. Following the administration of emedastine (2 mg b.i.d.) mean AUC0-24 values were 29.75 +/- 19.92 ng h ml(-1) and 46.13 +/- 38.50 ng h ml(-1) on day 1 and day 5, respectively. Histamine-induced wheals and flares were significantly more effectively suppressed by emedastine and cetirizine than placebo. At pharmacokinetic steady-state levels, no significant difference could be found in the potency between cetirizine and emedastine (2 mg b.i.d.). CONCLUSION: Emedastine displays pharmacodynamic properties comparable with cetirizine and therefore qualifies as a safe and alternative compound with H1-receptor antagonist properties. Additional larger studies may be needed to substantiate potential benefits of cetirizine over emedastine after single-dose administration.

Adult↗