Regional cerebral blood flow following single-dose and continuous-dose tadalafil after stroke

Purpose: Tadalafil is a potent and selective phosphodiesterase type 5 inhibitor that provides effective treatment for erectile dysfunction (ED). The purpose of this study was to explore the effect of a single on-demand dose of tadalafil compared to low-dose continuous administration on regional cerebral blood flow (rCBF), in patients after stroke. Methods: Thirty consecutive male patients (mean age 58.3 ± 7.9 years) with ED and a history of stroke were included in the study. The baseline single-photon emission computed tomography (SPECT) study was performed 15 min after iv injection of 740 MBq Tc-99m-HMPAO (Ceretec; GE Healthcare Ltd. Chalfont St. Giles, UK). Fifteen randomized patients received a single dose of 20 mg tadalafil in the morning, and a second SPECT study was performed 6 h later. Fifteen other patients received 5 mg of tadalafil each morning for seven consecutive days, and the second SPECT study was performed 6 h after the last dose. The imaging data were evaluated using SPM software (Wellcome Department of Cognitive Neurology, University College, London). Results: Associations between any of the risk factors/comorbidities and the perfusion changes were not detected. All patients showed areas of reduced relative rCBF in the affected hemisphere after tadalafil administration compared to baseline (P < 0.001). No significant difference was found between patients on 5 mg tadalafil and 20 mg dose. Conclusion: Tadalafil administration after cerebral stroke may be associated with diminished blood flow to areas adjacent to the stroke. The alterations in perfusion suggest a need for caution in prescribing tadalafil to patients with a history of stroke, especially with continuous administration that may impose constant stress on the cerebral circulation.