Sildenafil, a phosphodiesterase type 5 inhibitor, enhances the activity of two atypical antidepressant drugs, mianserin and tianeptine, in the forced swim test in mice

► Sildenafil is often used concurrently with antidepressant drugs. ► Effect of sildenafil on the activity of mianserin and tianeptine was investigated. ► Sildenafil enhanced the activity of mianserin and tianeptine in mice. ► Its interaction with mianserin was rather pharmacodynamic in nature. ► Its interaction with tianeptine has pharmacodynamic and/or pharmacokinetic basis.