Thyreostatic drugs

Thyreostatics, also known as antihormones, are drugs capable of inhibiting the production of thyroid hormones (123). One side effect of their use is the build up of water in muscle tissues and this property has led to their illegal use in some sections of the livestock industry to increase meat yield. 

When thyreostatic drugs are given to animals, the decreased production of thyroid hormones reduces basal metabolism, lowers gastrointestinal motility, and 

The result of the abuse of the thyreostatic drugs in animal production is not only the potential risk to human health of drug residues but also production of inferior quality meat. Furthermore, the consumer is deceived since water is sold for the price of meat. Consequently, a worldwide agreement has been promulgated prohibiting the use of these drugs in animal breeding (127). 

European Agency for the Evaluation of Medicinal Products (EMEA), in Natamycin, Summary Report, Committee for Veterinary Medicinal Products, EMEA/MRL/342/ 98-Final, London, UK (1998). 

Gibaldi, in Biopharmaceutics and Clinical Pharmacokinetics (M. Gibaldi, Ed.), 4th Edition, Lea Febiger, Philadelphia, PA (1991). 

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Fig. 8.8 Chemical structures of commonly used thyreostatic drugs.

The most important and powerful thyreostatic drugs used hitherto are the thiouracil analogues, such as thiouracil, methylthiouracil, propylthiouracil, and phenylthiouracil and die mercaptoimidazole analogues such as tapazole or methimazole. New thyreostatics as mercaptobenzimidazole are said to have been misused recently in some EU countries. 

G Vargas, J Havel, K Frgalova. Capillary zone electrophoresis determination of thyreostatic drugs in urine. J Capillary Electrophor 5 9-12, 1998. 

H.F. De Brabander, The Determination of Thyreostatic Drugs in Biological Mate rial, 1986, Ghent, Belgium, Ghent. 

Other drugs of lesser therapeutic importance can be classified into a series of minor classes including the antifungals, -adrenergic agonists, corticosteroids, diuretics, dyes, nonsteroidal anti-inflammatories, sedatives and -blockers, and thyreostatics. It is important to note that some drugs within the classes mentioned have dual function and can properly be classified in more than one of the above classes. As a result, overlap between drug classes is not unusual. 

A survey carried out in Austria between 1991 and 1993 demonstrated that the incidence of residues of veterinary drugs and hormones in edible tissues of slaughtered animals was almost negligible (7). In particular, urine samples obtained from calves, cows, and swine were tested for the presence of residues of stilbenes, zeranol, trenbolone and 19-nortestosterone. Blood samples were examined for 17- -estradiol and 17- -testosterone. Furthermore, urine samples from calves, beef cattle, and thyroid gland specimens were tested for the presence of -agonists and thyreostatic substances. None of the samples gave evidence of illegal use of these substances in Austria. 

Table 29,17 Physicochemical Methods for Corticosteroids, Thyreostatics, Diuretics and Non-Steroidal Anti-Inflammatory Drugs in Biological Matrices... 

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