Major Uses

Guaifenesin is an expectorant and muscle relaxant used in place of anesthesia for shorter procedures. It is used to induce muscle relaxation and restraint in large and small animals. There are also products that contain guaifenesin that are used for treating respiratory conditions.

Common Precautions

Guaifenesin should not be used on ruminants in concentrations higher than 5 percent, as it can cause hemolysis. The side effects of guaifenesin tend to be minor. The most common side effects are a mild decrease in blood pressure and increase in cardiac rate. There have been some cases of thrombophlebitis after injections of guaifenesin, and perivascular administration may cause tissue reactions.

Guaifenesin should not be used in animals with a known allergy or hypersensitivity to the drug. A veterinarian should be contacted immediately if an overdose is suspected, the symptoms of which may include apneustic breathing, nystagmus, hypotension, and contradictory muscle rigidity. Other symptoms can include hypothermia, mild tremors, ataxia, and vomiting in dogs. Cats can exhibit lethargy and anorexia as a result of an overdose.


Guaifenesin should be kept at room temperature and stored in a tight, light resistant, childproof container. When mixed in aqueous solutions, guaifenesin may precipitate out of the solution when exposed to temperatures below 72 degrees Fahrenheit. Slight warming and agitation will resolubilize the drug.


Guaifenesin is most commonly administered via intravenous injection and as a liquid mixture with other drugs. The common dose for a dog is 110 mg/kg as an injection and 50 mg/mL when mixed with ketamine and xylazine. For horses, a common dose is 110 mg/kg when administered in injection form, and 18-50 mg/kg when mixed with other drugs.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.