Histamine1 antagonists

Histamine 1 antagonists

Histamineantagonists bind to the receptor blocking the action of histamine. Earlierantagonists were rather non-selective leading to variable actions. Sedation wasa prominent adverse effect

of these drugs. Nowadays H1 and H2 selectiveantagonists are available. From the graphic their action can be deduced.

Itcould be expected that H1 antagonists would lead to bronchodilation due toblockade of smooth muscle contractions. However in practice this activity isnot clinically significant. These drugs can be used for amelioration of allergic rhinitis,conjunctivitis and eczema, but not of asthma.

1

H1 antagonists can lead to smooth muscle relaxation. 

2

H1 antagonists have an important role in the treatment of obstructive lung disease.