Sildenafil citrate (Viagra) reduces surface roughness of human erythrocytes: Atomic-force-microscopic study

Sildenafil citrate (Viagra) is used to treat erectile dysfunction and pulmonary arterial hypertension. The objective of this study was to analyze the action of sildenafil citrate on normal human erythrocytes in vitro at a concentration (2.5 mg/mL) higher than the prescribed for clinical conditions. Imaging of drug-treated erythrocytes was done using an atomic-force microscope in contact mode in air. Data analysis was performed using the scanning-probe-microscopy software WSxM. The study revealed that the drug causes hemolysis of erythrocytes at high concentration in vitro at room temperature. The ghosts (membranes) of erythrocytes with reduced cell size and deformed shape were observed using atomic-force-microscope imaging at low magnification. In addition, the high-magnification images revealed alterations in the nanostructural features of the erythrocyte membrane. There was a complete loss of characteristic membrane-architecture pattern. The root-mean-square surface roughness of the cell membrane after drug treatment was measured and found to be significantly less than that of erythrocytes in the native state. Sildenafil citrate causes hemolysis of erythrocytes in vitro at high concentration with significant alterations in morphometric properties, like change in cell shape, reduction in cell dimension, and disruption of membrane cytoarchitecture, along with a severe drop in membrane root-mean-square surface roughness.