Fenbendazole

What is this medication for?

• Ascarids, hookworms, whipworms, Taenia tapeworms (labeled); Giardia, lungworms, Paragonimus (extra-label)
• Ascarids, hookworms, Strongyloides, Taenia (extra-label — not FDA-approved in cats but considered safe/effective); Giardia, lungworms

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Single-dose treatment does not work — this is the most common practical dosing error; always counsel owners on completing the full 3-day (or longer) course.
• One of the safest anthelmintics available — appropriate first-line choice in pregnant/nursing animals and very young puppies/kittens.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Generally very well tolerated, good safety margin
• Salivation, vomiting, diarrhea (Infrequent)
• Hypersensitivity reaction (antigen release from dying parasites) (Possible, esp. high dosages)

Worth a phone call to your veterinarian

• Pancytopenia (Rare, isolated case report)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: None specific — considered safe in all ages including neonates
• has or has had: Single doses are NOT effective in dogs/cats — must treat ≥3 consecutive days for efficacy

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Bromsalan flukicides (not available in US)

Storage and handling

Tightly sealed container, protect from light, room temperature.

Good to know

• Single-dose treatment does not work — this is the most common practical dosing error; always counsel owners on completing the full 3-day (or longer) course.
• One of the safest anthelmintics available — appropriate first-line choice in pregnant/nursing animals and very young puppies/kittens.
• Not effective against Dipylidium caninum (flea tapeworm) — use praziquantel for that indication instead.