HISTAMINE RECEPTOR ANTAGONISTS
that competitively block histamine or act as inverse agonists at H1
receptors have been used in the treatment of allergic conditions for many
years, and in the discussion that follows are referred to as antagonists. Many
H1 antagonists are currently mar-keted in the USA. A large number
are available without prescrip-tion, both alone and in combination formulations
such as “cold pills” and “sleep aids” .