chemistry

Guaifenesin

Guaifenesin is a chemistry 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 Guaifenesin rather than just read about it. In short: Guaifenesin, also known as glyceryl guaiacolate, sold under the brand name Mucinex, among others, is an expectorant medication taken by mouth and marketed as an aid to eliminate sputum from the respiratory tract. Chemically, it is an ether of guaiacol and glycerine.

Key takeaways

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

Reference excerpt

Guaifenesin, also known as glyceryl guaiacolate, sold under the brand name Mucinex, among others, is an expectorant medication taken by mouth and marketed as an aid to eliminate sputum from the respiratory tract. Chemically, it is an ether of guaiacol and glycerine. It may be used in combination with other medications. A 2014 study found that guaifenesin does not affect sputum volume in upper respiratory infections (the upper respiratory system includes most breathing parts above the lungs). In 2023, it was alleged to work by making airway secretions more liquid. Side effects may include dizziness, sleepiness, skin rash, and nausea. While it has not been properly studied in pregnancy, it appears to be safe. Guaifenesin has been used medically since at least 1933. It is available as a generic medication and over-the-counter (OTC). In 2023, it was the 291st most commonly prescribed medication in the United States, with more than 500,000 prescriptions. In 2023, the combination dextromethorphan/guaifenesin was the 315th most commonly prescribed medication in the United States, with more than 200,000 prescriptions.

Medical uses Guaifenesin is used to try to help with coughing up thick mucus. It is sometimes combined with the antitussive (cough suppressant) dextromethorphan, such as in Mucinex DM or Robitussin DM. It is also combined with ephedrine in Primatene and Bronkaid tablets for symptomatic relief of asthma. Guaifenesin is combined with phenylephrine and paracetamol in certain Lemsip formulations. A Cochrane review identified three clinical trials assessing guaifenesin for the treatment of acute cough, with one finding significant benefit and the other two trials finding that it was not effective.

Side effects Although generally well-tolerated, side effects of guaifenesin may include an allergic reaction (rare), nausea, vomiting, dizziness, or headache.

Pharmacology

Mechanism of action Guaifenesin might act as an expectorant by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi via stimulation of the gastric mucosa. This stimulation leads to an increased parasympathetic activity in the respiratory tract via the so-called gastro-pulmonary reflex, although some in vitro studies suggested that it might also act directly on the respiratory epithelium. This increase in volume and reduction in viscosity aids in the flow of respiratory tract secretions, allowing ciliary movement to carry the loosened secretions upward toward the pharynx. Thus, guaifenesin may increase the efficiency of the cough reflex and facilitate the removal of the secretions. Additionally, guaifenesin has a demonstrated central antitussive effect.

History The Spanish encountered guaiacum wood when they conquered Santo Domingo, returning it to Europe where it was used in the 16th century as a supposed "cure" for syphilis and certain other diseases. The 1955 edition of the Textbook of Pharmacognosy states: "Guaiacum has a local stimulant action which is sometimes useful in sore throat. The resin is used in chronic gout and rheumatism, whilst the wood is an ingredient in the compound concentrated solution of sarsaparilla, which was formerly much used as an alterative in syphilis." Guaifenesin was first approved by the United States Food and Drug Administration in 1952. Although previously deemed "Generally Regarded as Safe" in its original approval, the drug received a New Drug Application for an extended-release version, which received approval on 12 July 2002. The FDA then issued letters to other manufacturers of timed-release guaifenesin to stop marketing their unapproved versions, leaving Adams Respiratory Therapeutics in control of the market. In 2007, Adams was acquired by Reckitt Benckiser. As of 2021, the drug is sold over-the-counter by many companies as a simple preparation and in combination with other OTC medications.

Veterinary use Guaifenesin's neurological properties first became known in the late 1940s. Guaifenesin is a centrally acting muscle relaxant used routinely in large-animal veterinary surgery. Guaifenesin is used in combination with, for example, ketamine, since guaifenesin does not provide analgesia or produce unconsciousness. In horses, the drug's biological half-life is 77 minutes. Premedication with xylazine (1.1 mg/kg) can reduce the dose required from 163 mg/kg (in geldings) to just 88 mg/kg.

Society and culture

Brand names Guaifenesin is taken by mouth, and is supplied as a tablet, a capsule, an extended-release (long-acting) tablet, dissolving granules, and a syrup. It is available under many brand names, as either the sole active ingredient or part of a combination drug. Drugs combined with guaifenesin in over-the-counter preparations include the cough-suppressant dextromethorphan, analgesics such as paracetamol/acetaminophen, and decongestants such as ephedrine, pseudoephedrine, or phenylephrine.

Economics In 2014, sales of guaifenesin were estimated to be approximately $135 million per year in the United States.

Illustrations

Worked examples

Example 1 — a first encounter with Guaifenesin

Start with the simplest possible case. Write down what Guaifenesin 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 Guaifenesin 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 Guaifenesin 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 Guaifenesin

In research: Guaifenesin 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 Guaifenesin 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: Guaifenesin is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2-Methoxyphenyl compounds, Catechol ethers, Drugs with unknown mechanisms of action, so understanding it makes those chapters shorter.
In everyday life: Look for Guaifenesin 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 Guaifenesin in 20 minutes

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

Frequently asked questions

What is Guaifenesin in simple terms?

Why does Guaifenesin 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 Guaifenesin?

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 Guaifenesin.