Tranquilizers (sedatives) are sedative drugs. A few may be used in animal husbandry.

If tranquilizers are used, they can enter the organism and thus animal foods.

Three tranquilizers appear in Table 1 of Regulation (EU) No. 37/2010, which establishes the classification of pharmacologically active substances with regard to maximum residue limits in food of animal origin, and are therefore permitted: Azaperone with a sum limit of azaperone and its metabolite azaperol, carazolol and xylazine.

Chlorpromazine is listed in Table 2 of Regulation (EU) No. 37/2010 and is therefore among the explicitly prohibited substances.

Unauthorized tranquilizers are substances that are not listed in the regulation. These may not be used in food-producing animals. These include acepromazine, haloperidol and propionylpromazine.

Food (kidneys from slaughtered animals) is tested annually for tranquilizer residues under the National Residue Control Plan.

Metabolism

Some foreign substances (e.g. also drugs) are chemically modified in the organism by enzymes. If the metabolic reactions take place to a not inconsiderable extent, not only the original drugs but also their metabolites are defined as marker residues and aggregate limits are set for them (as in the case of azaperone, for example).

The drug group of phenothiazines, which includes tranquilizers such as chlorpromazine and acepromazine, form a large number of metabolites.

Xylazine is metabolized very rapidly in the liver and excreted via the kidney (70%) or bile (30%). The half-life in plasma is one to six minutes.

Analyses and range of tests

In the Department of Veterinary Drugs, Hormones and Contaminants of the Institute for Food Safety Vienna, we analyze tranquilizers in animal tissues and are also the National Reference Laboratory for these investigations.

After suitable sample preparation, the following tranquilizers are analyzed by high-pressure liquid chromatography with mass spectrometric detection (LC-MSMS):

• Azaperone and Azaperol
• Acepromazine
• Carazolol
• Chlorpromazine
• Haloperidol
• Propionylpromazine
• Xylazine

The highest tranquilizer concentrations are usually detected in the kidney. Therefore, kidney samples are routinely analyzed, and in rare cases, muscle samples are also analyzed.