This does not comply with the recommendations of the current guidance document (CVMP/ VICH/ 832/ 99), ‘ where pharmacokinetic parameters cannot demonstrate a relationship with effectiveness, two dose confirmation studies using the dose limiting parasite for therapeutic claims ….. will be needed .’ For dose confirmation studies, ‘ at least two controlled or, where appropriate, critical dose confirmation studies ….. are recommended. ’ Efficacy could be claimed if effectiveness against each parasite declared on the labelling was at 90% or above based on calculation of geometric means and there was a statistically significant difference in parasite numbers between control and treated horses.