Tiamulin hydrogen fumarate--veterinary uses and HPLC method of determination in premixes and medicated feeding stuffs.

Approved antimicrobial substances were treated as feed additives and used also as growth promoters until 2006. Regulation No 1831/2003 of the European Parliament and of the Council of 22 September 2003 on additives for use in animal nutrition changed the situation and at the moment antibiotics in feeds, except coccidiostats and histomonostats, can be used only as medicated feedingstuff. Medicated feedingstuffs are produced only on prescription from approved premixes in authorized manufacturing place. In agreement with EU and Polish legislation, both production process and usage of medicated feedingstuff has to be strictly monitored and controlled. The main aims of the control process are determination of active ingredient concentration, homogeneity of the product and accordance with GMP. Among antimicrobials mainly used in veterinary medicine are tetracyclines, amoxicillin, tylosin, tiamulin and sulfonamides. Tiamulin hydrogen fumarate is widely used semisynthetic drug included in pleuromutilin class of antibiotics (1, 2). Its antibacterial properties are stronger than those of natural pleuromutilin, extracted from Pleurotus mutilus (Fr.) Sacc. and Pleurotus Passeckerianus Pil. (3). For a long period of time tiamulin was considered the only pleuromutilin antibiotic in use and in veterinary medicine exclusively. Lately two more drugs were added to this group: valnemulin in veterinary applications and retapamulin approved for human use in dermatological infections. Tiamulin is mainly used for swine and poultry but has also some application in cattle, goats and sheep treatment. Its antibacterial activity against Mycoplasma spp., Gram positive bacteria such as streptococci and staphylococci and obligate anaerobes is well known. Tiamulin is a drug of choice in treatment of swine dysentery caused by Brachyspira hyodeysentreiae and bacterial pneumonia caused by Pasteurella multicida. It is also used in porcine intestinal adenomatosis (Lawsonia intracellularis), arthritis (Mycoplasma hyosynoviae, M. bovis) and chronic sinusitis (2ñ5). The mechanism of tiamulin bacteriostatic activity, as well as other pleuromutilins, is based on blockage of protein synthesis in bacterial cell. Thanks to its strong affinity to 23 rRNA in 50S ribosomal subunit tiamulin joins to peptidyl transferase centre during initiation of translation, inhibiting peptide bond formation at this point of the process (6, 7). This antibiotic does not affect peptide binding when elongation has started. Tiamulin resistance is rare but emerging and cross-resistance to tylosin and erythromycin occurs (2). It is probably due to mutations in ribosomal L3 protein as well as in 23rRNA itself, which leads to higher flexibility of peptidyl transferase centre region and ability to overcome tiamulin inhibition (6, 7). Tiamulin is a base sparingly soluble in water more often used as hydrogen fumarate salt, what increases its solubility dramatically. Diterpenic core of the molecule consists of three rings: cyclo-pen-