Histamine and its Effects Mediated via H₃ Receptor – Potential Clinical Applications of H₃ Antagonists

Histamine is one of the most important biogenic amines and it mediates numbers of physiological processes. It is also involved in majority of inflammatory diseases via its receptors H₁, H₂, H₃ and H₄. The role of histamine had been recognized as substantial in many allergic diseases including bronchial asthma, thus the histamine receptor antagonists (H₁) are frequently used in the clinical practice as potent anti-allergic and anti-inflammatory drugs. However, first generation of antihistamines have also adverse effects, predominantly sedation, changes in appetite and many more, and they are still not fully effective in all patients. Attention is now focused mainly on H₃ and H₄ receptor antagonists and their potential clinical applications. This review focuses basically on the H₃ receptor, its expression pattern and some effects which are mediated by H₃, discussing its clinical relevance