Iloprost is a medication used to treat pulmonary arterial hypertension and other related conditions. Stable isotopes of iloprost are non-radioactive forms of the drug that are used for research purposes. These isotopes have the same chemical properties as the regular form of iloprost, but with a different atomic weight, allowing for accurate tracking and analysis in biological systems. The use of stable isotopes of iloprost in research can help to better understand the pharmacokinetics and metabolism of the drug, as well as aid in drug discovery and development.