Of course! The problem is that when laypeople buy veterinary doses (because you can't get a package of human pills for a decent price), it's very easy to underestimate the effective concentration of the medicine. There's also a risk that the material the effective ingredient is wrapped in (flavouring, gelling agents, etc.) doesn't go down well with the human body, or that the higher concentration has an effect on the human body.

If you compensate for the body weight and ensure that the gel agent the animal medicine comes in doesn't have any adverse effects on the human body (it probably doesn't) then consuming animal medicine can be an excellent way to treat parasitic infections if you're awfully poor and don't qualify for any insurance. Consuming any chemical not made for human consumption is dangerous, but if you don't have another option, it's better than doing nothing.

People ridicule the whole horse dewormer story, but it's no secret that people around the world have turned to animal medicine out of necessity due to prices of medication.