[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Eicosanoids: prostaglandins, thromboxanes and leukotrienes as drug targets # Eicosanoids: prostaglandins, thromboxanes and leukotrienes as drug targets The lipid messengers made from arachidonic acid, and the anti-inflammatories, antiplatelet drugs, asthma drugs and prostaglandin analogues that act on them. Updated Nov 2, 2026 Eicosanoids are short-lived signals made on demand from arachidonic acid released from cell membranes. Cyclooxygenase (COX) makes prostaglandins and thromboxane; 5-lipoxygenase makes leukotrienes. The chemistry of these pathways is on the Biochemistry page «Eicosanoids»; this page covers the drugs that block or copy them. ## Key points - Phospholipase A2 frees arachidonic acid; COX-1 and COX-2 turn it into prostaglandin H2, the parent of the other prostanoids. - NSAIDs block COX; corticosteroids act further upstream and reduce both prostaglandins and leukotrienes. - Aspirin acetylates COX irreversibly; platelets cannot make new enzyme, so thromboxane A2 stays low for the life of the platelet. - Prostaglandins protect the stomach lining and keep kidney blood flow up when it is under stress: blocking them explains NSAID ulcers and kidney injury. - Leukotriene receptor antagonists (montelukast) and the 5-lipoxygenase inhibitor zileuton treat asthma; prostaglandin analogues are used in obstetrics, glaucoma, ulcers and pulmonary hypertension. ## The pathway in brief Arachidonic acid can go down two main roads. The COX road gives prostaglandins (PGE2, PGF2α, PGD2), prostacyclin (PGI2, made by vessel walls; it dilates vessels and stops platelets) and thromboxane A2 (made by platelets; it constricts vessels and makes platelets clump). The lipoxygenase road gives leukotrienes: LTB4 attracts neutrophils, and the cysteinyl leukotrienes (LTC4, LTD4, LTE4) constrict airways and make vessels leak. ## Blocking prostaglandins: NSAIDs and coxibs COX-1 is present in most tissues all the time (stomach, kidney, platelets); COX-2 is induced by inflammation but also has normal roles in the kidney and vessel wall. Non-selective NSAIDs block both, which relieves pain, fever and inflammation but brings stomach ulcers, bleeding and kidney effects. COX-2 selective drugs (celecoxib) spare the stomach somewhat, but they reduce vascular prostacyclin more than platelet thromboxane, which fits with their raised cardiovascular risk. - Aspirin: irreversible; at low doses mainly antiplatelet - Indometacin and ibuprofen can close a patent ductus arteriosus in newborns, because prostaglandins keep it open - Late in pregnancy NSAIDs can narrow the fetal ductus ## Copying prostaglandins: analogues - Misoprostol (PGE1 analogue): protects the stomach from NSAIDs; it also contracts the uterus, so it is dangerous in pregnancy unless used for an obstetric purpose - Carboprost (PGF2α analogue) and misoprostol: uterine contraction in postpartum haemorrhage - Latanoprost (PGF2α analogue): eye drops that increase aqueous outflow in glaucoma - Alprostadil (PGE1): keeps the ductus arteriosus open in some newborn heart defects - Epoprostenol (prostacyclin): vasodilator for pulmonary arterial hypertension ## Leukotrienes and asthma Montelukast blocks the cysteinyl leukotriene receptor (CysLT1); zileuton blocks 5-lipoxygenase. Both help in asthma, especially aspirin-exacerbated respiratory disease, in which blocking COX shunts arachidonic acid toward leukotrienes. Montelukast carries a warning about neuropsychiatric effects. ## Memory aid «Prostacyclin Protects vessels, Thromboxane Thickens platelets»; aspirin tips the balance because platelets cannot rebuild COX. ## Test yourself Think of the answer, then tap the question to see it. ## Why does one dose of aspirin affect platelets for days? Aspirin acetylates COX irreversibly, and platelets have no nucleus to make new enzyme, so thromboxane A2 stays low until new platelets are released. ## Why can NSAIDs trigger asthma attacks in some patients? Blocking COX diverts arachidonic acid toward the lipoxygenase pathway, raising bronchoconstricting cysteinyl leukotrienes. ## What are two clinical uses of prostaglandin analogues? Any two of: protecting the stomach (misoprostol), postpartum haemorrhage (carboprost, misoprostol), glaucoma (latanoprost), keeping the ductus arteriosus open (alprostadil), pulmonary arterial hypertension (epoprostenol). ## Why do NSAIDs threaten the kidney in dehydration or heart failure? In these states kidney blood flow depends on vasodilating prostaglandins; blocking them can lower filtration and cause acute kidney injury. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes-as-drug-targets/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Example drugs - [Acetylsalicylic acid](https://durgical.com/en/pharmacology/acetylsalicylic-acid/) - [Ibuprofen](https://durgical.com/en/pharmacology/ibuprofen/) - [Celecoxib](https://durgical.com/en/pharmacology/celecoxib/) - [Indometacin](https://durgical.com/en/pharmacology/indometacin/) - [Misoprostol](https://durgical.com/en/pharmacology/misoprostol/) - [Carboprost](https://durgical.com/en/pharmacology/carboprost/) - [Montelukast](https://durgical.com/en/pharmacology/montelukast/) - [Latanoprost](https://durgical.com/en/pharmacology/latanoprost/) - [Alprostadil](https://durgical.com/en/pharmacology/alprostadil/) - [Epoprostenol](https://durgical.com/en/pharmacology/epoprostenol/) ## Connections ## Related classes 5 - [Nonsteroidal anti-inflammatory drugs (NSAIDs)](https://durgical.com/en/pharmacology/classes/nonsteroidal-anti-inflammatory-drugs/) - [Prostaglandin analogues (obstetric use)](https://durgical.com/en/pharmacology/classes/prostaglandin-analogues/) - [Leukotriene modifiers](https://durgical.com/en/pharmacology/classes/leukotriene-modifiers/) - [Corticosteroids (glucocorticoids)](https://durgical.com/en/pharmacology/classes/corticosteroids/) - [Antiplatelet drugs](https://durgical.com/en/pharmacology/classes/antiplatelet-drugs/) [← All of pharmacology](https://durgical.com/en/pharmacology/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Misoprostol: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a689009.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [Montelukast: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a600014.html) (MedlinePlus (U.S. National Library of Medicine), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes-as-drug-targets/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes-as-drug-targets/