Toltrazuril is a triazinon derivative and an antiprotozoal agent. It has coccidiocidal activity against all intracellular development stages of the genus Cystoisospora, that is, merogony (asexual multiplication) and gamogony (sexual phase).

Iron is an essential micronutrient. It is a constituent of haemoglobin and myoglobin and has a key role in enzymes, such as cytochromes, catalases, and peroxidases. Piglets are born with only moderate stores of iron and the milk consumed by piglets is a poor source of iron. In intensive farming conditions, piglets do not have access to other sources of iron, such as soil. Therefore, piglets should be supplemented with iron.

After a single intramuscular injection of the recommended dose rate of 20 mg toltrazuril per kg body weight to piglets, toltrazuril plasma pharmacokinetics are characterised by biological variability.

Toltrazuril reaches peak plasma concentrations of 4.17 to 6.43 mg/I within 5 days. Total plasma exposure reaches between 1046 and 1245 mg*h/l. Toltrazuril is eliminated from plasma with a half­ life of about 3 to 4 days showing substantial metabolism to toltrazuril-sulfoxide and toltrazuril­sulfone, the main active metabolite. Toltrazuril-sulfone shows plasma peak concentrations of 6.23 to 8.08 mg/l at 11 to 15 days after injection of the parent drug. Total plasma exposure reaches 3868 to 4097 mg*h/l. Toltrazuril-sulfone is eliminated from plasma with a half-life of about 5 to 7 days. Toltrazuril and its metabolites are mainly eliminated in faeces via biliary excretion and to a small extent via urine.

After intramuscular injection, the iron complex is absorbed mainly into the lymphatic tissue, where it is split to release iron (III)-ions . Plasma iron concentration peaks within the first day reaching concentrations of 548 mg/I at 6 hours after injection. Free iron (III)-ions are removed from plasma with a half-life of approximately 8 hours. From 72 h onwards, this is followed by a very slowly decreasing plasma concentration with a calculated mean half-life of 960 h, indicating equilibrium conditions. In the blood, free iron (III)-ions bind to transferrin (transport form) and are mainly used for the synthesis of haemoglobin. The iron (III)-ions are stored as ferritin in the main storage organs (e.g. liver, spleen and the reticuloendothelial system), and iron elimination does not play a quantitatively important role. There is no specific organ for iron excretion. Iron is not readily eliminated; most of it is re-used, while only small amounts are eliminated. The primary routes of iron excretion are via faeces and urine, there are additional small losses in sweat, hair and nails.