Tamsulosin and risk of priapism: A causality assessment using Austin Bradford Hill Criteria

Tamsulosin hydrochloride, a selective alpha-adrenergic blocking agent has been previously associated with priapism. Priapism is a medically serious condition that, if not intervened, can cause permanent erectile dysfunction. This study was conducted to investigate whether the association of tamsulosin and priapism is causal. All currently available evidence such as experimental, biological, toxicological, published studies, and safety data mined from the WHO global pharmacovigilance database was systematically organized into the Austin Bradford Hill causality assessment framework. In the international pharmacovigilance database, a strong association between tamsulosin and priapism (IC₀₂₅ = 4.1; PRR₀₂₅ = 19.9; ROR₀₂₅ = 20) was observed. There were 122 cases of priapism associated with tamsulosin submitted to the database from 23 countries. In 87.7% of the cases, tamsulosin was reported as a ‘sole suspect,’ and in 50.8%, it was the only drug administered. In several patients, priapism resolved following discontinuation of tamsulosin and recurred after its reintroduction. Both in the published and unpublished data, for majority of the cases, the time to onset of priapism was within few days following the first intake of tamsulosin. Cases of priapism, particularly those published, were consistent in their clinical features with patients experiencing prolonged painful erection that required aspiration of cavernosal blood, irrigation of the corpora cavernosa, and treatment with vasopressors. Other alpha-adrenergic blocking agents that are structurally analogous with tamsulosin have also been associated with priapism. In several cases, tamsulosin was used off-label, for the treatment of ureteral calculi expulsion. Eight patients experienced priapism that ended up with serious complications such as ejaculation disorders and erectile dysfunction. The currently available totality of evidence suggests that the association of tamsulosin and priapism is causal. Healthcare professionals are therefore recommended to cautiously prescribe tamsulosin and ensure that consumers are aware of the potential risk of priapism.