ABSTRACT
Phenoxybenzamine (CAS 59-96-1) and phentolamine (Rogitine, Alliance; CAS 50-602; Figure 5.1) are, respectively, long-and short-acting α-adrenoceptor antagonists and cause peripheral vasodilatation. Phentolamine also has a direct action on vascular smooth muscle. These drugs are used to treat severe hypertension due to amphetamines, cocaine, clonidine, methylphenidate, monoamine oxidase inhibitors (MAOIs), oxedrine and phenylephrine. The use of β-blockers in such instances would lead to unopposed αstimulation and hence worsened hypertension.
