Astemizole
Astemizole (marketed under the brand name Hismanal, developmental code R43512) was a second-generation antihistamine drug that has a long duration of action. Astemizole was discovered by Janssen Pharmaceutica in 1977. It has been withdrawn from the market in most countries because of rare but potentially fatal side effects (QTc interval prolongation and related arrhythmias due to hERG channel blockade).
Histidine decarboxylase
Antihistamines are a class of medications designed to reduce unwanted effects of histamine in the body. Typical antihistamines block specific histamine receptors, depending on what physiological purpose they serve. For example, diphenhydramine (Benadryl™), targets and inhibits the H1 histamine receptor to relieve symptoms of allergic reactions. Inhibitors of histidine decarboxylase can conceivably be used as atypical antihistamines. Tritoqualine, as well as various catechins, such as epigallocatechin-3-gallate, a major component of green tea, have been shown to target HDC and histamine-producing cells, reducing histamine levels and providing anti-inflammatory, anti-tumoral, and anti-angiogenic effects.