Veterinary Use

Similar medicines derived from the guaiac tree were in use as a generic remedy by Native Americans when explorers reached North America in the 1500s, but guaifenesin was first approved by the Food and Drug Administration (FDA) in 1952.

Guaifenesin is a centrally acting muscle-relaxant that is used as a part of many anesthetic protocols in the horse. Its mechanism of action is not precisely known but the relaxation of skeletal muscles, mild analgesic and mild sedative properties allows for lower doses of other sedatives and anesthetic agents. Guaifenesin is used for induction before inhalation anesthesia, during inhalation anesthesia and with total intravenous anesthesia (TIVA) for short procedures. Guaifenesin has minimal effects on diaphragmatic function and produces relatively little respiratory depression at normal doses. It is used primarily in horses although it has been studied and is used in other domestic species.

Guaifenesin also was called glyceryl guaiacolate, GG and a number of other similar chemical-names. Guaifenesin is compatible with D-5-W and sterile water. It usually is reconstituted before each use. Warming and agitation will help resolubilize the drug, particularly in cold temperatures.


Guaifenesin is used in veterinary hospitals as a part of the induction protocol for inhalation anesthesia. It commonly is used after sedation with an alpha agonist drug, followed by ketamine. Other drugs including benzodiazepines, butorphanol, thiopental and other barbiturate drugs may be added at the anesthesiologist’s discretion. Induction and recovery generally are smooth.

Guaifenesin also is used in the field or in veterinary hospitals for TIVA for procedures lasting less than an hour. Anesthesia is induced using an alpha agonist such as xylazine, detomidine or romifidine followed by ketamine. Guaifenesin (5%) solution is combined with additional alpha agonist and ketamine to create what commonly is called “Triple Drip.” This combination is used to prolong anesthesia up to an hour. The degree of muscle relaxation and quality of recovery generally is good with the Triple-Drip protocols. Further information regarding drug concentrations and dose rates may be found in veterinary anesthesia textbooks.

Guaifenesin within a Triple Drip combination also is administered with inhalant anesthesia as a means of reducing the total amount of inhalant used in a given case. This combination of intravenous and inhalant anesthesia is referred to as “balanced anesthesia.” Balanced anesthesia has the advantages of less cardiovascular depression, diminished need for additional drugs to support hemodynamics and improved recoveries.

Guaifenesin Side Effects

  •  Guaifenesin may cause a mild decrease in blood pressure and an increase in heart rate.
  •  There are conflicting reports regarding hemolysis and reactions of the vascular endothelium with higher concentration solutions of guaifenesin.


  •  ARCI Class 4 drug.
  •  Guaifenesin has been shown to cross the placenta. Neonatal levels immediately after delivery were about 30% of the level in the mare. TIVA with Triple Drip has been used successfully in field situations for dystocia. Appropriate ventilation and respiratory support for the foal may be necessary.
  •  Donkeys and to a lesser extent mules may be more sensitive to guaifenesin. Mules are reported to be intermediate between horses and donkeys.
  •  Perivascular administration will cause tissue reaction. Guaifenesin should be administered using an intravenous catheter.

Drug Interactions

Anticholinesterase drugs such as physostigmine are contraindicated. (Plumb 2005)


Guaifenesin is relatively safe. The margin of safety is reported to be three times the normal dose and cardiovascular side-effects are rare. Signs of overdose include apneustic breathing, nystagmus, hypotension and increased muscle-rigidity. Although there is no specific antidote, Guaifenesin has a relatively short half-life (60 to 85 minutes) (Plumb 2005). Supportive treatment should be instituted while the drug is being cleared.

Treating Cat Cough with Guaifenesin

Cat cough is a relatively minor disease in that it rarely poses a real risk for the affected animal, although it can be an uncomfortable affliction, and it can easily pass from cat to cat. One of the many treatments available for cats that suffer from cat cough is a drug called guaifenesin . Guaifenesin is usually only used in more severe cases of respiratory infection, and it is sold over the counter in most drugstores.

Causes and Symptoms of Cat Cough

Cat cough can be caused by a range of things, including simple and temporary problems that do not require treatment, such as hairballs or mild throat irritation, as well as more persistent problems, such as bacterial infection, viral infection or allergies. Of course, the most obvious symptom is coughing. You can recognize that a cat is coughing when the animal makes frequent hacking noises from his mouth or throat. Coughs can be either dry and hacking, or moist and slimy. Other possible symptoms that cats may display when they are suffering from cat cough include nasal or ocular discharge. Sometimes, affected felines will also run a high fever, but this symptom is rarely detected by pet owners because it requires an anal thermometer reading to detect.

Treatment with Guaifenesin

Guaifenesin is classified as an expectorant drug, which means that it works by both reducing the amount of phlegm and mucous secreted by the trachea and bronchi in the cat’s respiratory passageways, and reducing the viscosity of the remaining secretions. In this way, guaifenesin relieves chest congestion and opens up the respiratory tracts, making it easier for the cat to breathe. It is speculated that, by reducing respiratory secretions and making them more fluid, this drug also increases coughing efficiency, because it is easier for the cat to cough up the reduced amount of excess phlegm.

How to Administer Guaifenesin

Guaifenesin for cats comes in liquid form, so the best way to give guaifenesin to your cat is to mix the syrup in some wet food. The recommended dose depends on the cat’s weight: half of a milliliter of guaifenesin for every pound that the animal weighs. Guaifenesin rarely produces any side effects, but cats that were given the drug have been known to experience nausea and vomiting. In very rare cases, cats have been recorded to be allergic to guaifenesin. Some possible allergic reactions to this drug are irritated, itchy rashes with hives, difficulty breathing, tightness in the chest, or swelling of the face, particularly the mouth area. If your cat displays any symptoms of an allergy to guaifenesin, discontinue administration immediately.

If your cat is suffering from a case of cat cough, do not be too quick to administer medication, because cat cough is not a very dangerous disease, and it often resolves itself after a few days on its own. However, if your cat is suffering severely from a case of cat cough, and the symptoms do not seem to be going away, you can administer drugs such as guaifenesin to help relieve some of your pet’s symptoms.

Guaifenesin enhances the analgesic potency of paracetamol in mice



Guaifenesin is used as an expectorant and it has been reported to possess muscle relaxant and sedative activity. Guaifenesin has been used as a component of composite OTC analgesics containing paracetamol for many years. The aim of our study was to ascertain effects of guaifenesin on paracetamol analgesic activity and locomotor performance.


Antinociceptive efficacy was tested in mice using an acetic acid (0.7%) writhing test. Locomotor performance was tested in rota-rod test and activity cage. All drugs were given orally and tested in mice.


In combination with a subeffective dose of guaifenesin (200 mg/kg), the ED(50) for paracetamol in the writhing test was significantly lower (82.2 mg/kg) than that of paracetamol administered alone (233.7 mg/kg). Guaifenesin alone did not show an analgesic effect. Guaifenesin did not produce statistically significant locomotor impairment in the rota-rod test at doses enhancing analgesic activity of paracetamol, although there was a trend for decreased locomotor activity in activity cage.


The present results indicate that guaifenesin may enhance analgesic activity of paracetamol.

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  •  Consider cognitive-behavioral therapy to learn how to cope with symptoms and stress.
  •  Try acupuncture or massage.
  •  Try the Feldenkrais Method for gentle exercises to help correct poor posture or habits of movement that may contribute to pain.
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