Key result
Single oral doses of propanolol, dilevalol, and salbutamol did not significantly alter retinal vessel diameter or volumetric blood flow compared to placebo in normotensive diabetic volunteers.
Why the study?
Do single oral doses of propranolol, dilevalol, or salbutamol alter retinal blood flow or intraocular pressure compared to placebo in normotensive diabetic volunteers?
RCT
Do single oral doses of propranolol, dilevalol, or salbutamol alter retinal blood flow or intraocular pressure compared to placebo in normotensive diabetic volunteers?
Single doses of beta-blockers with varying receptor affinities do not significantly alter retinal blood flow in normotensive diabetic patients, despite reducing systemic or intraocular pressure.
These agents leave retinal hemodynamics unchanged in normotensive diabetics; confirms absence of direct retinal vascular effects despite IOP or systemic pressure changes.
The effect of a single oral dose of propanolol 80 mg, dilevalol 200 mg, salbutamol 4 mg, and placebo on the systolic (BPs), diastolic blood (BPd), intraocular pressure (IOP), on retinal vessel diameter (D), blood velocity (Vmax) and volumetric retinal blood flow (RBF), was measured at baseline, 90 minutes and three hours after administration in normotensive diabetic volunteers. These drugs were chosen to demonstrate a range of beta receptor activity. Propanolol is a non-specific beta blocker, affecting beta 1 and beta 2 receptors, dilevalol has beta 1 antagonist and beta 2 agonist effects and salbutamol has beta 2 agonist effects. Retinal blood flow was measured by bidirectional laser Doppler velocimetry (BLDV) and red free photography. Dilevalol reduced the mean BPs by 10.4 mmHg (SD 4.2, P less than 0.05), the mean BPd by 7 mmHg (SD 3.8, P less than 0.05), whereas propanolol, salbutamol and placebo had no significant effect. Propanolol reduced the mean intraocular pressure by 4.88 mmHg (SD 1.8, P less than 0.01). No treatment had a significant effect on retinal perfusion pressure. In all treatments the vessel diameter and volumetric flow remained unchanged, and there was no significant difference between the treatments. The mechanisms of action of these drugs are analysed and the possible implications of their use in patients with retinal disease are discussed.
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Newsom et al. (1991) conducted an RCT in Normotensive diabetes. Propanolol, dilevalol, and salbutamol vs. Placebo was evaluated on Retinal vessel diameter and volumetric retinal blood flow. Single oral doses of propanolol, dilevalol, and salbutamol did not significantly alter retinal vessel diameter or volumetric blood flow compared to placebo in normotensive diabetic volunteers.
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