Fish mox & sinus infection

Updated November 21, 2016

Antibiotics are a ubiquitous class of medications used to treat bacterial infections in all vertebrate animals, from fish to folks. Humans and animals use many parallel medications, sometimes for the same purposes and in comparable doses. Fish Mox, for example, is a 250-mg capsule of amoxicillin, an antibiotic available in the same dosage for people. It seems reasonable to save a trip to the doctor's office and treat a sinus infection inexpensively, but experts say it may not be the best idea.

The Facts

Fish Mox is the brand name of a form of amoxicillin that Thomas Laboratories of Tolleson, Arizona, makes for use in home aquariums. According to the manufacturer, Fish Mox works against pathogentic bacteria that affect ornamental fish, and can be used to treat infected eyes, pop-eye, fin or tail rot, skin ulcerations, columnaris disease and gill disease. Each capsule contains 250 mg of amoxicillin, to be dissolved into the aquarium---one capsule for every 10 gallons of water. Thomas Laboratories specifically states that Fish Mox is for aquarium use only and not for use with other animals or by humans.


Amoxicillin for adult humans is available in capsules, tablets or in powder to dissolve. It also comes in a suspension for children. Amoxicillin is part of the penicillin family of antibiotics, and can cause serious allergic reactions.

Sinus Infections

A sinus infection is one of many common conditions doctors treat with antibiotics such as amoxicillin. When saline nasal sprays and irrigation systems, over-the-counter decongestants and pain relievers such as acetaminophen and ibuprofen are not enough, a bacterial infection may be the culprit. As with any medication, patients should follow doctor's instructions exactly, keep taking the medicine for the full period prescribed even if symptoms disappear, and not take the medicine for any other condition, no matter how similar the symptoms may be.

Expert Insight

Fish Mox is amoxicillin, and the capsule comes in a dosage that could translate into human requirements. Some people go to pet stores or online to purchase Fish Mox, which is cheaper than human antibiotics (especially for those who don't have health insurance) and does not require a prescription. Veterinary medications, however, are not as refined as those formulated for humans. According to doctors, the risk of adverse reactions is higher than with the more strictly controlled amoxicillin for people. While you could theoretically treat a sinus infection with Fish Mox, experts such as Don Klingborg, DVM, associate dean of public programs at the University of California at Davis School of Veterinary Medicine, recommend against it.


People in need of antibiotics can visit a free or reduced-cost clinic, where the doctor may prescribe amoxicillin at low or no cost. Some of the larger pharmacy chains, such as Giant Foods and Publix, offer a free 14-day supply of certain generic antibiotics, such as amoxicillin.

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