Telithromycin

Key takeaways

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

Reference excerpt

Telithromycin is the first ketolide antibiotic to enter clinical use and is sold under the brand name of Ketek. It is used to treat community acquired pneumonia of mild to moderate severity. After significant safety concerns, the US Food and Drug Administration sharply curtailed the approved uses of the drug in early 2007. Telithromycin is a semi-synthetic erythromycin derivative. It is created by substituting a ketogroup for the cladinose sugar and adding a carbamate ring in the lactone ring. An alkyl-aryl moiety is attached to this carbamate ring. Furthermore, the oxygen at the 6 position is methylated, as is the case with clarithromycin, to achieve better acid-stability. It was patented in 1994 and approved for medical use in 2001.

Adverse effects Most common side-effects are gastrointestinal, including diarrhea, nausea, abdominal pain and vomiting. Headache and disturbances in taste also occur. Less common side-effects include palpitations, blurred vision, and rashes. Prolonged QTc intervals may also be caused by telithromycin. Rare but severe side-effects were initially reported in March 2006, involving damage to the liver. Three different incidents were reported: one case of temporary drug-induced hepatitis, one ending in a liver transplant, and one ending in death. In the United States, the FDA's Office of Epidemiology and Surveillance identified 12 cases of acute liver failure, resulting in four deaths, and an additional 23 cases of acute, serious liver injury, among 5.2 million patients taking telithromycin through April 2006. In 2010, a published report described the likely mechanism of action underlying not only the cases of liver failure but also cases of visual disturbances and exacerbations of myasthenia gravis. The study showed that a pyridine moiety that is part of the telithromycin molecule acts as an antagonist on cholinergic receptors located in the neuromuscular junction, the ciliary ganglion of the eye and the vagus nerve innervating the liver. Other macrolides, such as azithromycin and clarithromycin and the fluoroketolide, solithromycin, do not contain the pyridine moiety and do not antagonize these cholinergic receptors significantly.

Mechanism of action Telithromycin prevents bacteria from growing, by interfering with their protein synthesis. Telithromycin binds to the subunit 50S of the bacterial ribosome, and blocks the progression of the growing polypeptide chain. Telithromycin has over 10 times higher affinity to the subunit 50S than erythromycin. In addition, telithromycin strongly bind simultaneously to two domains of 23S RNA of the 50 S ribosomal subunit, where older macrolides bind strongly only to one domain and weakly to the second domain. Like many other protein synthesis inhibitors, telithromycin can also inhibit the formation of ribosomal subunits 50S and 30S.

Pharmacokinetics Unlike erythromycin, telithromycin is acid-stable and can therefore be taken orally while being protected from gastric acids. It is fairly rapidly absorbed, and diffused into most tissues and phagocytes. Due to the high concentration in phagocytes, telithromycin is actively transported to the site of infection. During active phagocytosis, large concentrations of telithromycin is released. The concentration of telithromycin in the tissues is much higher than in plasma. Telithromycin fulfills a role that has arisen due to the rise of microbial resistance to existing macrolides and appears to be effective against macrolide-resistant Streptococcus pneumoniae. The defining differentiating characteristic of the ketolides as opposed to other macrolides is the removal of the neutral sugar, L-cladinose from the 3 position of the macrolide ring and the subsequent oxidation of the 3-hydroxyl to a 3-keto functional group.

Metabolism Telithromycin is metabolized mainly in the liver, the main elimination route being the bile, a small portion is also excreted into the urine. About one third is excreted unchanged in bile and urine, the biliary route being favoured. Telithromycin's half-life is approximately ten hours.

History French pharmaceutical company Hoechst Marion Roussel (later Sanofi-Aventis) began phase II/III clinical trials of telithromycin (HMR-3647) in 1998. Telithromycin was approved by the European Commission in July 2001 and subsequently went on sale in October 2001. In the US, telithromycin received U.S. Food and Drug Administration (FDA) approval on April 1, 2004.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Telithromycin

Start with the simplest possible case. Write down what Telithromycin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Telithromycin 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 Telithromycin 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 Telithromycin

In research: Telithromycin appears in chemistry 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 Telithromycin 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: Telithromycin is common in secondary-school and first-year university syllabi. It links to neighbouring topics 3-Pyridyl compounds, CYP3A4 inhibitors, Carbamates, so understanding it makes those chapters shorter.
In everyday life: Look for Telithromycin 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.

How to study Telithromycin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Telithromycin 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 Telithromycin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Telithromycin in simple terms?

Telithromycin is the first ketolide antibiotic to enter clinical use and is sold under the brand name of Ketek. It is used to treat community acquired pneumonia of mild to moderate severity.

Why does Telithromycin matter?

Because it connects several chemistry 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 Telithromycin?

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 Telithromycin.