Please note that we can’t give veterinary advice here. We are not vets. If you feel at all uncertain about the dosage, please contact your vet and ask.
Not all vets recommend treatment for pinworms in rabbits. Pinworms are not considered a health threat to the rabbit. My vet says she treats, because it doesnt feel nice for the owner if their bun has worms.
Fenbendazole is effective against pinworms. Normal dosage is 20 mg per kilo body weight and day. The dewormer is to be given for 5 days, then nothing for five days, then dewormer again for five more days.
Fenbendazole strenght is often written as 10% which means 100 mg per ml. I don’t know if the horse paste also contains 100 mg per ml. It could perhaps be difficult to measure up with a syringe since it is a paste, but a syringe can be loaded from the back if you pull out the plunger. The paste in the syringe can be packed by hitting the loaded syringe against the table to try and get as much air as possible out. If the strength is 100 mg per ml, 1,5-2 pound buns should get about 0.2 ml each.
(A horse would need 5 mg fenbendazole per kilo body weight and day (a lower dose per kilo than a rabbit needs). If the strenght of the Safeguard fenbendazole you have is 100 mg per ml, that means a 600 kilo horse would need 30 ml of the fenbendazole paste per day. Does this seem to fit with the info on the Safeguard fenbendazole you have?)