Hypoxic pulmonary hypertension (HPH) and iptakalim, a novel ATP-sensitive potassium channel opener targeting smaller arteries in hypertension.
Hypoxic pulmonary hypertension (HPH) is a serious and potentially devastating chronic disorder of the pulmonary circulation. Attempts to use drugs in the therapy of hypoxic pulmonary hypertension indicated the importance of prevention or reduction of vasoconstriction as well as of the reversal of remodeling within the cardiovascular system. Iptakalim (2,3-dimethyl-N-(1-methylethyl)-2-butylamine), a novel ATP-sensitive potassium channel opener, has the desired effects on hypoxic pulmonary arteries. Iptakalim decreases the elevated mean pressure in pulmonary arteries, and attenuates remodeling in the right ventricle, pulmonary arteries and airways. Moreover, iptakalim has selective antihypertensive effects: it significantly lowers arterial pressure in hypertensive animals, but has little if any effect in normotensive animals. In HPH iptakalim has selective effects on smaller arteries. Long-term iptakalim therapy decreases expression of sulfonylurea receptor 2 and of mRNA of inwardly rectifying potassium channel in smaller arteries of spontaneously hypertensive rats. Iptakalim inhibits the effects of endothelin-1, reduces the intracellular calcium concentration and inhibits the cell cycle in smooth muscle cells of pulmonary arteries. There is no evidence for the development of tolerance to the long-lasting antihypertensive action of iptakalim. At therapeutic doses iptakalim has no effects on the central nervous, respiratory, digestive, or endocrine systems. It has a broad therapeutic range, so that it can be safely used in the therapy of HPH.