[Concerning the toxicity of parbendazole (Helmatac 30) to horses and ponies (author’s transl)].

The study explores the toxicity of parbendazole in horses and ponies, and it found that the severity of side effects depends on the dosage used. Still, when administered at half the therapeutic dose on two consecutive days, it resulted in minimal toxic symptoms and was highly efficient at treating gastro-intestinal nematodes.

Methodology and Findings

• The researchers studied the effects of different dosages of parbendazole on 52 horses and 16 ponies. The participants were selected and divided into twelve groups.
• The key side effects observed were laxation (soft dung, diarrhoea), anorexia (loss of appetite), and listlessness. The severity of these symptoms was determined by the dosage administered.
• It was observed during the study that administering half the therapeutic dose of parbendazole (2.5 to 3.75 mg/kg) on two consecutive days generally led to minor toxic symptoms and was highly effective against gastro-intestinal nematodes in horses and ponies.

Recommendations and Additional Observations

• The use of “standard powders” (not commercially available as such) is recommended for straightforward dosing. This approach could also help prevent overdosing as much as possible.
• The study also found that the laxative side effect of parbendazole was extensive amid work or movement.
• The study involved eight Shetland ponies that were in various stages of pregnancy, from the fourth up to the eleventh month. No adverse effect on the pregnancy or the development of the fetus was observed from the medication administration.
• After the treatment with parbendazole, no evidence of hyperlipaemia (excess amount of fat in the blood) was revealed through either clinical examination or clinical chemical serum examination.