science

Sitaxentan

Sitaxentan is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sitaxentan rather than just read about it. In short: Sitaxentan sodium (TBC-11251) is a medication for the treatment of pulmonary arterial hypertension (PAH). It was marketed as Thelin by Encysive Pharmaceuticals until Pfizer purchased Encysive in February 2008.

Key takeaways

Sitaxentan belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sitaxentan to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sitaxentan from memory before moving on to harder problems.

Reference excerpt

Sitaxentan sodium (TBC-11251) is a medication for the treatment of pulmonary arterial hypertension (PAH). It was marketed as Thelin by Encysive Pharmaceuticals until Pfizer purchased Encysive in February 2008. In 2010, Pfizer voluntarily removed sitaxentan from the market due to concerns about liver toxicity.

Mechanism of action Sitaxentan is a small molecule that blocks the action of endothelin (ET) on the endothelin-A (ETA) receptor selectively (by a factor of 6000 compared with the ETB). It is a sulfonamide class endothelin receptor antagonist (ERA) and is undergoing Food and Drug Administration (FDA) review for treating pulmonary hypertension. The rationale for benefit compared with bosentan, a nonselective ET blocker, is negligible inhibition of the beneficial effects of ETB stimulation, such as nitric oxide production and clearance of ET from circulation. In clinical trials, the efficacy of sitaxentan has been much the same as bosentan, but the hepatotoxicity of sitaxentan outweighs its benefits. Dosing is once daily, as opposed to twice daily for bosentan.

Regulatory status On December 10, 2010 Pfizer announced it would be withdrawing sitaxentan worldwide (both from marketing and from all clinical study use), citing that it is a cause of fatal liver damage. Sitaxentan was approved for marketing in the European Union in 2006, in Canada in 2006 and in Australia in 2007. By February 2008 it had been launched commercially in Germany, Austria, The Netherlands, the United Kingdom, Ireland, France, Spain and Italy. In March 2006, the FDA recommended an approvable status to sitaxentan but said it would not yet approve the product. In July 2006, sitaxentan received a second approvable letter stating that efficacy outcome issues raised in the context of the STRIDE-2 study were still unresolved. In July 2007, Encysive commenced a formal dispute resolution process in a preliminary meeting with the FDA. In September 2007 the company announced that it was making preparations for another phase III clinical trial (intended to be named STRIDE-5) to overcome the FDA's concerns. The takeover by Pfizer resulted in a reconfiguration and extension of these plans, to include combination therapy with sildenafil. The Sitaxentan Efficacy and Safety Trial With a Randomized Prospective Assessment of Adding Sildenafil (SR-PAAS) was an ongoing program of three clinical trials conducted in the United States (ClinicalTtrials.gov identifiers: NCT00795639, NCT00796666 and NCT00796510) with anticipated completion dates between June 2010 and January 2014.

Adverse effects Adverse effects observed with sitaxentan are class effects of endothelin receptor antagonists, and include :

liver enzyme abnormalities (increased ALT and AST) headache edema constipation nasal congestion upper respiratory tract infection dizziness insomnia flushing Because sitaxentan inhibits metabolism of warfarin, a decreased dose of warfarin is needed when co-administered with sitaxentan. This is because warfarin acts to prevent blood from clotting, and if it remains unmetabolized, it can continue to thin the blood.

References

Illustrations

Worked examples

Example 1 — a first encounter with Sitaxentan

Start with the simplest possible case. Write down what Sitaxentan claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sitaxentan before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sitaxentan ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sitaxentan

In research: Sitaxentan appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sitaxentan in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sitaxentan is common in secondary-school and first-year university syllabi. It links to neighbouring topics Benzodioxoles, Chloroarenes, Endothelin receptor antagonists, so understanding it makes those chapters shorter.
In everyday life: Look for Sitaxentan outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sitaxentan in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sitaxentan means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sitaxentan out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sitaxentan in simple terms?

Why does Sitaxentan matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sitaxentan?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sitaxentan.