Which of the following can reverse one or more smooth muscle effects of circulating histamine in humans?
Granisetron
Adrenaline
Ranitidine
Sumatriptan
Adrenaline is a physiological antagonist of histamine. It reverses bronchoconstriction caused by histamine. Ranitidine is an H2 antagonist that decreases gastric acid secretion but has no effect on smooth muscles.