Trial reportEuropean journal of applied physiology2026
Oral phosphodiesterase-5 inhibitor does not augment red blood cell deformability at rest or during handgrip exercise.
Trial report in European journal of applied physiology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
purposeRed blood cells (RBCs) rely on deformability for oxygen delivery and capillary transit. Sildenafil citrate, a phosphodiesterase-5 inhibitor (PDE5-i), may enhance RBC deformability via nitric oxide, yet in vivo effects remain unclear.
methodsWe conducted a double-blind, placebo-controlled study to assess the effects of PDE5-i on cerebral blood flow (CBF), brachial artery (BA) blood flow (Q) and shear stress-specific RBC deformability during handgrip exercise (Baseline [BL], 27.5% and 55% of maximal voluntary contraction [MVC]). Fourteen participants (8F; age: 24 ± 6) were tested on separate days, before and 60-min following ingestion of sildenafil citrate (100 mg) or placebo. CBF and BA Q were measured using duplex ultrasound and RBC deformability was assessed with a laser-assisted optical rotational red cell analyzer.
resultsAcute oral administration of PDE5-i had no effect on basal cerebral or BA vascular metrics, including diameter, shear stress, Q, BA shear stress-specific RBC deformability or exercise hyperemia (p > 0.05). Prior to PDE5-i administration, exercise increased RBC deformability [EImax] (BL: 0.55 ± 0.021; 27.5% MVC: 0.57 ± 0.014; 55% MVC: 0.58 ± 0.015 a.u. p < 0.01). However, despite exercise-induced increases in EImax (BL: 0.59 ± 0.018 a.u. p < 0.01), PDE5-i did not further modify this parameter during a subsequent-bout of handgrip exercise (27.5%: 0.59 ± 0.017; 55%: 0.59 ± 0.015 a.u. p > 0.05), a pattern not observed with placebo. EImax did not differ between PDE5-i and placebo at matched exercise intensities post-administration (p > 0.05), indicating no independent effect of PDE5-i on RBC deformability.
conclusionAcute PDE5-i administration does not independently alter RBC deformability or vascular responses, at rest or during handgrip exercise in healthy individuals.
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