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Prostacyclin (also called prostaglandin I2 or PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.
Read the full article on WikipediaA plain-language summary of the cited sources below. Informational only — not medical advice.
Epoprostenol is a medication used to treat pulmonary arterial hypertension, a condition where blood pressure in the arteries of the lungs is dangerously high. It works by mimicking a natural substance your body makes called prostacyclin, which healthy blood vessels normally release to keep blood flowing smoothly.
When epoprostenol enters the bloodstream, it attaches to specific receptors on the surface of platelets (the cells that help blood clot) and on the walls of blood vessels. This triggers a chain reaction inside these cells that produces a chemical messenger called cAMP. In platelets, this messenger stops them from clumping together unnecessarily. In the muscle cells surrounding blood vessels, it causes the muscles to relax, which widens the vessels and lowers blood pressure.
The medication has an extremely short half-life of 42 seconds, which means half of the dose breaks down in the body within less than a minute. Because it acts and disappears so quickly, epoprostenol must be given as a continuous infusion directly into a vein—it cannot be taken as a tablet or given as occasional injections.
Your family member's treating doctor has prescribed this medication to manage their pulmonary arterial hypertension. The very short duration of action means the effects wear off rapidly if the infusion is interrupted, which is why the delivery system and backup plans are critical parts of the treatment.
Pulmonary arterial hypertension (PAH) Clinical criteria: Treatment Phase: Initial 1 (new patients) Patient must not have received prior PBS-subsidised treatment with a pulmonary arterial hypertension (PAH) agent, AND Patient must have WHO Functional Class IV PAH, AND The treatment must be the sole PBS-subsidised PAH agent for this condition. Treatment criteria: Must be treated by a physician with expertise in the management of PAH, with this authority application to be completed by the physician with expertise in PAH. A prior PAH agent is any of: ambrisentan, bosentan, macitentan, sildenafil, tadalafil, epoprostenol, iloprost, riociguat. Applications for authorisation of initial treatment must be made via the Online PBS Authorities System (real time assessment) or in writing via HPOS form upload or mail. If the application is submitted through HPOS form upload or mail, it must include: (a) details of the proposed prescription; and (b) a completed authority application form relevant to the indication and treatment phase (the latest version is located on the website specified in the Administrative Advice). (1) Confirm that the patient has a diagnosis of pulmonary arterial hypertension (PAH) in line with the following definition: (a) mean pulmonary artery pressure (mPAP) at least 25 mmHg at rest and pulmonary artery wedge pressure (PAWP) no greater than 15 mmHg; or (b) where right heart catheterisation (RHC) cannot be performed on clinical grounds, right ventricular systolic pressure assessed by echocardiography (ECHO) is greater than 40 mmHg, with normal left ventricular function. (2) Confirm that in forming the diagnosis of PAH, the following tests have been conducted: - RHC composite assessment; and - ECHO composite assessment; and - 6 Minute Walk Test (6MWT) Where it is not possible to perform all 3 tests on clinical grounds, the expected test combination, in descending order, is: - RHC plus ECHO composite assessments; - RHC composite assessment plus 6MWT; - RHC composite assessment only. In circumstances where RHC cannot be performed on clinical grounds, the expected test combination, in descending order, is: - ECHO composite assessment plus 6MWT; - ECHO composite assessment only. (3) Document the findings of these tests in the patient's medical records, including, where relevant only, the reason/s: (i) for why fewer than 3 tests are able to be performed on clinical grounds; (ii) why RHC cannot be performed on clinical grounds - confirm this by obtaining a second opinion from another PAH physician or cardiologist with expertise in the management of PAH; document that this has occurred in the patient's medical records. (4) Confirm that the test results are of a recency that the PAH physician making this authority application is satisfied that the diagnosis of PAH is current. (5) Confirm that this authority application is not seeking subsidy for a patient with pulmonary hypertension secondary to interstitial lung disease associated with connective tissue disease, where the total lung capacity is less than 70% of predicted. The test results must not be more than 6 months old at the time of application. The maximum quantity authorised will be limited to provide sufficient supply for 1 month of treatment, based on the dosage recommendations in the Therapeutic Goods Administration (TGA) approved Product Information. A maximum of 5 repeats may be requested.
“As mentioned above, prostacyclin (PGI2) is released by healthy endothelial cells and performs its function through a paracrine signaling cascade that involves G protein-coupled receptors on nearby platelets and endothelial cells. The platelet Gs protein-coupled receptor (prostacyclin receptor) is activated when it binds to PGI2. This activation, in turn, signals adenylyl cyclase to produce cAMP. cAMP goes on to inhibit any undue platelet activation (in order to promote circulation) and also counteracts any increase in cytosolic calcium levels that would result from thromboxane A2 (TXA2) binding (leading to platelet activation and subsequent coagulation). PGI2 also binds to endothelial prostacyclin receptors, and in the same manner, raises cAMP levels in the cytosol. This cAMP then goes on to activate protein kinase A (PKA). PKA then continues the cascade by promoting the phosphorylation of the myosin light chain kinase, which inhibits it and leads to smooth muscle relaxation and vasodilation. It can be noted that PGI2 and TXA2 work as physiological antagonists.”
“42 seconds”
A plain-language summary of the cited sources below. Informational only — not medical advice.
Epoprostenol is a prostacyclin analogue classified among platelet aggregation inhibitors. It is TGA-approved for pulmonary arterial hypertension. The drug acts as a synthetic prostacyclin (PGI2), binding to Gs protein-coupled prostacyclin receptors on platelets and vascular endothelium. Receptor activation stimulates adenylyl cyclase to raise intracellular cAMP, which inhibits platelet activation and—via protein kinase A phosphorylation of myosin light-chain kinase—promotes smooth muscle relaxation and vasodilation. Epoprostenol functionally antagonises thromboxane A2.
The plasma half-life is 42 seconds, necessitating continuous intravenous infusion. This ultra-short duration of action reflects rapid enzymatic degradation and demands uninterrupted delivery; abrupt cessation risks rebound pulmonary hypertension.
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