Histological Study on the Effects of Sildenafil (Viagra) versus Tadalafil (Diamonrecta) on Retina of Non-diabetic and Induced Untreated Diabetic Rat models

Diabetes mellitus is a common multisystem disorder. Retinopathy is one of its common complications together with erectile dysfunction (ED). Phosphodiesterase 5 inhibitors are the first line therapy in diabetic induced ED and reported to cause ocular changes.Objective: To elucidate how Tadalafil and Sildenafil affect the retina in non-diabetic and untreated diabetic rats.Materials & Methods: Sixty adult male albino rats were organized into six groups (ten rats each). The experiment period was 8 weeks: Group I was a control. Group II received Sildenafil at a dose of (10mg/kg /day) orally. Group III received Tadalafil at a dose of (2.6mg/kg/day) orally. Group IV was intraperitoneally injected by a single dose of 150 mg/kg of Alloxan for induction of Diabetes and left to the experiment end without any treatment. Alloxan was injected intraperitoneally to group V& group VI once to induce diabetes, one day after Diabetes confirmation; they received Sildenafil as group II &Tadalafil as group III respectively. By the experiment end, the rats were weighed; blood samples were collected to estimate blood glucose level and oxidative stress biomarkers. Extraction and preparation of retina for histological examination were done.Results: Diabetic group (IV) revealed a highly significant decline in body weight, SOD & catalase levels while MDA was highly significantly elevated. Degenerative changes of retinal layers with marked variation in retinal thickness and strong positive response for caspase 3 were remarked. There were signs of neovascularization in VEGF immunostaining. Electron microscopic examination & statistical analysis confirmed these changes. Sildenafil & Tadalafil administration showed beneficial effects on diabetic retinopathy. Tadalafil was more effective than Sildenafil.Conclusion: Sildenafil &Tadalafil are safe drugs for ED treatment in diabetics. As they give some changes in the non-diabetic animals (group II&III), retinal monitoring is essential and drug cessation is recommended if any visual downsides arise.