Chronical treatment with sildenafil causes Achilles tendinopathy in rats

Abstract Aims The primary goal was to assess the effects of chronic sildenafil treatment over the Achilles tendons in rats. Main methods Animals were divided into two groups, control and sildenafil administration ( n  = 5). After 60 days, the tendons were subject to biochemical and image analysis to compare tendons between the groups: collagen I and decorin content, polarisation microscopy and birefringence analysis, and tissue zymography. Key findings The animals exposed to sildenafil presented a much less organised tendon matrix, with reduced collagen I and non-collagenous protein content and a much higher decorin content. Significance The results observed in the animals can be characterised as tendinopathy, a condition not yet described as a sildenafil side effect.