Iloprost in Pulmonary Aerial Hypeension is administered:
**Core Concept**
Iloprost is a prostacyclin analogue used in the treatment of pulmonary arterial hypertension (PAH). It works by inducing vasodilation through the activation of adenylyl cyclase, leading to increased levels of cyclic adenosine monophosphate (cAMP) in vascular smooth muscle cells.
**Why the Correct Answer is Right**
Iloprost exerts its effects by stimulating the prostacyclin receptor, which is a G protein-coupled receptor that activates adenylyl cyclase, resulting in the increased production of cAMP. This increase in cAMP causes vascular smooth muscle cells to relax, leading to vasodilation and a decrease in pulmonary artery pressure. Iloprost is administered through inhalation, allowing for direct delivery to the lungs and minimizing systemic side effects.
**Why Each Wrong Option is Incorrect**
* **Option A:** Iloprost is not administered orally, as this would lead to significant systemic side effects and decreased efficacy due to first-pass metabolism.
* **Option B:** Iloprost is not a phosphodiesterase-5 inhibitor, which is a different class of medication used to treat PAH, such as sildenafil.
* **Option C:** Iloprost is not a calcium channel blocker, which is another type of medication used to treat PAH, such as nifedipine.
**Clinical Pearl / High-Yield Fact**
Iloprost is a potent vasodilator that should be used with caution in patients with a history of asthma or other respiratory diseases, as it can exacerbate bronchospasm.
**Correct Answer:** D.