The U.S. Food and Drug Administration has approved Ayradia to treat Giardia duodenalis infections in dogs, making the prescription medication the first of its kind for any animal species.
Ayradia (metronidazole oral suspension) has antibacterial and antiprotozoal properties, according to the sponsor, Virbac Animal Health. The medication is administered orally and twice daily with a supplied syringe for five consecutive days.
Virbac conducted two studies:
- Laboratory: Ayradia was more than 99% effective at reducing Giardia trophozoites in treated dogs. Young, healthy male and female beagles were given either Ayradia or sterile water orally twice daily for five consecutive days. Four days after the last treatment, Giardia trophozoites were counted in each dog’s small intestine. Dogs treated with Ayradia had significantly lower trophozoite counts than the control dogs.
- Field: Ayradia was more than 99% effective at reducing Giardia cysts in treated dogs. Privately owned and shelter dogs with naturally occurring Giardia infections received either Ayradia or a vehicle control for five consecutive days. The vehicle control contained all of Ayradia’s inactive ingredients but no metronidazole. Fecal samples were obtained from each dog on three consecutive days before and after treatment. Giardia cysts were counted using fecal immunofluorescent or indirect fluorescent antibody assay. Dogs in the treated group had significantly fewer cysts than those in the control group.
Safety studies included:
- Higher than labeled dose and duration: Young, healthy male and female beagles were administered Ayradia at up to three times the labeled dose for 15 consecutive days or five times the labeled dose for five consecutive days. Dogs that received five times as much experienced a higher incidence of ear erythema and diarrhea than the other groups, but the signs resolved without treatment.
- Labeled dose and duration: Client-owned dogs with naturally occurring Giardia infections were treated with Ayradia or another antiprotozoal drug at the labeled dose and duration. The most common adverse effects in the Ayradia-treated dogs were vomiting and diarrhea, which resolved without treatment.
Ayradia might cause skin irritation, especially in people with a known sensitivity to metronidazole or other nitroimidazole products. Therefore, Virbac advises avoiding contact with a treated dog’s saliva for at least five minutes after administration. If skin contact occurs, the area should be washed with soap and water.