The α1-adrenoceptors (ADRA1A, B and D) are involved in smooth muscle contraction when activated by their endogenous catecholamine ligands norepinephrine and epinephrine. Blood vessels with these receptors are present in the skin, GI sphincters, kidney, brain and urinary bladder. In prostate, the ADRA1A subtype mediates prostate contraction. Blockade of these receptors with synthetic antagonists is the mechanism of action of agents used in the treatment of hypertension (Nash 1990) and benign prostatic hyperplasia (BPH).

Synthesized in 1974, prazosin was the first selective α1-blocker that was approved to treat hypertension (Schnaper & Oberman 1975, Adriaensen & Vryens 1975). It is a sympatholytic medication, thus mediating the sympathetic nervous system which plays a role in blood pressure regulation. As well as treating hypertension, it is also used to treat anxiety and post-traumatic stress disorder (PTSD) (Raskind et al. 2000, Taylor & Raskind 2002, Keeshin et al. 2017). Although not a first line choice for either hypertension or benign prostatic hyperplasia, it is a choice for patients who present with both problems concomitantly (Mathur et al. 2014). Terazosin works by blocking the action of adrenaline on smooth muscle of the bladder and the blood vessel walls thus can be used in the treatment of hypertension (Itskovitz 1994) and BPH (Guthrie 1994, Roehrborn et al. 1996). Doxazosin is an α1 adrenoceptor-selective blocker used to treat hypertension and urinary retention associated with benign prostatic hyperplasia (BPH) (Torvik & Madsbu 1986, Guthrie & Siegel 1999, Kaplan et al. 1995).