Fostedil (KB-944) is a phosphonic acid derivative with potent vasodilator activity. KB-944 has been demonstrated to produce long lasting coronary vasodilator and hypotensive effects in conscious and anesthetized dogs; increase coronary blood flow in isolated, blood perfused heart preparations of dogs; and reduce systemic pressure in conscious normotensive and hypertensive rats. Slow channel calcium entry blockade is thought to contribute to the vasodilator activity of KB-944. Fostedil is longer acting in hypertensive animals than either nifedipine or diltiazem suggesting a potential clinical advantage for this compound. Unexpectedly, fostedil was shown to produce atrial fibrillation in 3 of 10 hypertensive patients in a placebo controlled study. Fostedil had been in phase II clinical trials for the treatment of angina pectoris. However, this research has been discontinued.

Temelastine (also known as SK&F 93944) is a competitive histamine H1-receptor antagonist, which does not penetrate the central nervous system. This drug was studied as an anti-allergic agent. Experiments on animals have shown that the drug was efficacious vs. pharmacologic and antigen-induced bronchoconstriction.

Etintidine is a potent competitive antagonist of histamine H2-receptors. It has a low level of antiandrogenic activity. Etintidine was being investigated in the treatment of peptic ulcer, however, its development has been discontinued.

Noberastine (NOB), a histamine H1 antagonist, has potent and specific peripheral antihistaminic activity. Noberastine, a furan derivative of nor-astemizole (an astemizole metabolite), has been shown to have a more rapid onset, and shorter duration of action than astemizole with peak antihistaminic activity at 4h following ingestion. Noberastine is rapidly absorbed and the peak plasma levels are obtained within 2 h of oral dosing. In preclinical studies Noberastine has been shown to lack central nervous system effects. After subacute (steady-state) administration of noberastine, there was increasing inhibition of weal and flare formation with higher doses of the drug. The 30 mg daily dose showed maximum antihistaminic effects.

Venritidine [D 16637] is an H2-antagonist which appears to undergo phase I clinical trials in the United Kingdom and preclinical investigation in Germany as a gastric ulcer treatment.

Napactadine is a bicyclic antidepressant agent. It is a histamine-H1 receptor antagonist. Preliminary results indicated a marked improvement in depressive symptomalology within 7 days of treatment, as measured by the Hamilton depression scale. However, clinical studies were discontinued after chronic administration of napactadine because an elevation in liver enzyme levels was observed in some patients.

Etolotifen is an antiasthmatic agent.

Dacemazine is a derivative of phenothiazine which acts as an antagonist of a histamine H1 receptor. The compound demonstrates local anesthetic activity and reduced the spasms produced by acetylcholine and histamine. In combination with di-tert-butylnaphthalenesulfonate, dacemazine was marketed under tradename Codopectyl as a spasmolytic and antitussive agent.

Perastine is an antihistaminic agent.

Eclazolast (REV 2871 or CHBZ) is a non-disodium cromoglycate (DSCG)-like, antiallergic drug. Eclazolast is taken up by rat mast cells and human leukocytes in a specific and saturable manner. The compound can be hydrolyzed by a granule-associated enzyme in the mast cell to an ionic metabolite (REV 3579) whose in vitro profile is identical to that of DSCG. Eclazolast is a potent inhibitor of both immunologic and non-immunologic histamine release. It inhibits exocytosis by intracellularly affecting only direct Fc(epsilon)RI linked processes and not through inhibition of Ca2+ influx channels.