I spend a lot of time talking about antimicrobial misconceptions and dogmas. They are a big issue, because they often lead to unnecessary or excessive duration of antimicrobial use, use of more invasive routes of administration (e.g. intravenous over oral), or use of higher-tier antimicrobials than necessary.

I’ll just address one of these misconceptions today: Doxycycline should be avoided in young growing animals because of teeth staining and bone development.

Nope.

The concern about using doxycycline in young animals relates to calcium binding. Tetracycline and some of the older drugs in this class have substantial calcium binding and use of some tetracyclines has been shown to impact the development of teeth in various species, including dogs. It’s even sometimes used in wildlife rabies vaccine baits as a way to help determine if an animal ingested a bait when it was younger, because the tetracycline will cause detectable staining of the teeth.

Doxycycline is different. It doesn’t bind calcium to the same degree as other drugs in this class, so we can’t assume that what happens with other tetracyclines also applies to doxycycline.

Staining of teeth is a major concern in humans, so we can look there for some guidance. They’ve had the same dogma (i.e. avoid doxycycline in kids) for decades, but it’s been challenged and efforts are underway to refute it.

• There’s one study looking at the effects of doxycycline use in kids treated for Rocky Mountain spotted fever, a potentially severe tick borne disease for which doxycycline is the treatment of choice. It wasn’t a huge study (58 kids) but it found no evidence of dental staining, enamel hypoplasia, or tooth color differences due to doxycycline treatment.

• A review and commentary about kids and malaria stated, “It is time to rehabilitate doxycycline and to recommend it for malaria treatment in children under 8 years of age” because it is “a cheap drug with a broad therapeutic spectrum and very little evidence of serious adverse events.”

• The US CDC has also raised the concern that “Misperceptions about the use of doxycycline for children prevent kids from getting lifesaving treatment.“ They also address the issue of unsubstantiated warnings on drug labels: “Despite the current label warning, it is important for healthcare providers to know that doxycycline has not been shown to cause tooth staining in the dose and duration used to treat rickettsial diseases. Early administration of doxycycline in adults and children can prevent severe illness and save lives.”

• The American Academy of Pediatrics states “Although data are limited, evidence does not support dental staining as a consequence of doxycycline use in young children.” They recommend doxycycline for a variety of conditions in young kids, particularly tickborne diseases.

So, while we’re lacking data for dogs, information from other species shows that we shouldn’t be concerned about staining teeth or related effects in young animals, and we should therefore use doxycycline when it’s indicated even in young patients, as it is a lower-tier, safe and effective antimicrobial.

Unsubstantiated (or clearly disproven) dogmas persist in medicine (human and veterinary) and they’re really hard to address. However, we have to try to address them because they can cause harm.