Phentolamine

**Semantic type:** Organic Chemical|Pharmacologic Substance

**Definition:** A synthetic imidazoline with alpha-adrenergic antagonist activity. As a competitive alpha-adrenergic antagonist, phentolamine binds to alpha-1 and alpha-2 receptors, resulting in a decrease in peripheral vascular resistance and vasodilatation. This agent also may block 5-hydroxytryptamine (5-HT) receptors and stimulate release of histamine from mast cells.

**Synonyms:** - 2-[N-p'-Tolyl-N-(m'-hydroxyphenyl)aminomethyl]imidazoline - 2-[N-p'-Tolyl-N-(m'-hydroxyphenyl)aminomethyl]imidazoline - PHENTOLAMINE