Studies are underway investigating the addition of a third agent, the intravenous prostanoid epoprostenol.
正在进行以添加第三种药物的研究，即静脉注射的前列腺素类花青素。
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For patients whose disease is still not well-controlled, studies are underway investigating the addition of a third agent, the intravenous prostanoid epoprostenol.