mrls for veterinary medicines in live animals in march 2013 panama expressed its concern with regard to the notification submitted by costa rica on national directive senasa-dg-d003-2011 on mrls for medicines in live animals g sps n cri 136 . although the directive was notified in january 2013 it had been in place since november 2011. panama asked costa rica to explain how it had provided for a reasonable period of time for members to make comments how those comments were taken into account and how its trading partners had been informed about the content of the directive. given that the mrls established by the new directive were taken from the codex alimentarius for liver tissues limit of 100ig k and from the fda for muscle tissues limit of 10ig k panama also requested costa rica to explain how it performed the calculations to obtain an accurate quantitative measurement of a single tissue when the sample analysed was a processed product that might contain mixed portions of different tissues. costa rica replied that an sps notification was required only when new measures were not based on international standards. given that costa ricas new directive set the same mrls that were established by the codex alimentarius and by the fda there was no need to notify it in advance or to provide a timeframe for comments before the implementation of the directive. however for transparency purposes costa rica had decided to notify the measure in january 2013. costa rica also explained that its trading partners had been aware of costa ricas mrls for veterinary medicines since 2008 when the central american regulation on residues and veterinary medicaments was notified to the wto g sps n cri 69 . the regulation established that the mrls for veterinary medicines were those set by the codex alimentarius or by the fda when they were not listed in the codex alimentarius. with regard to processed products costa rica noted that no mrls were set for animal by-products by the codex alimentarius or by any other international agency hence mrls of raw material had to be taken as parameters. in this case the raw material for processed meat products would be the muscle tissue. costa rica highlighted the specific case of the ivermectin dewormer that was a very dangerous active principle for human health because of its high lipid solubility its persistence in the animal body and its ability to cross the nerve barriers. costa rica had established the mrl for ivermectin in muscle tissue at 10ig k to protect consumers health. this mrl allowed the identification of animals that were treated with the medication and which were sent to slaughter too early without complying with the established withdrawal period. an hplc method with fluorescence detection was used to test the ivermectin levels in liver and muscle tissues. additionally fortified samples were used to ensure control alongside the use of good laboratory practices.