Sulfonamides confirmation

Among one of the more unusual side effects noticed as the use of the sulfonamides became widespread was the increased urine output of many patients treated with these drugs. The fact that the urine was unusually alkaline led to the suspicion, later (Confirmed by independent means, that these agents were responsible for partial inhibition of the enzyme carbonic anhydrase. Inhibition of this enzyme causes increased excretion of sodium and bicarbonate ions as well as water, in effect bringing about diure-... 

The data from the 2000 FSIS/USDA monitoring program (Table 12.4) present very similar results to those found in the 1998 data (USDA, 2000). For the sake of simplicity, the data presented show the violations and the upper 95% confidence limits. These data confirm the consistently low incidence of antibiotic and sulfonamide residues in animals grown for food. Even in the worst-case situation, the upper range of the violative incidence remains relatively low, usually less than 2%. There are some hot spots, namely in veal calves, hogs, and horses. Horses appear to be a special case because these animals are rarely used for food in the U.S. It may be that horses are treated with antibiotics or antimicrobials to ensure the animals or carcasses are in the best shape for marketing. 

FSIS laboratories also use chemical techniques and instrumentation to identify select antibiotic residues. The tetracyclines of interest are identified by thin layer chromatography. Sulfonamides are detected and quantified by fluorescence thin lay chromatography and confirmed by gas chromatography/mass spectrometry. Amoxicillin and gentamycin are identified and/or quantified by high pressure liquid chromatography. Similar techniques are used to identify ionophores and other antimicrobials of interest. 

Minocycline is an effective alternative to rifampin for eradication of meningococci, including sulfonamide-resistant strains, from the nasopharynx. However, the high incidence of dose-related vestibular side effects renders it less acceptable. Although minocychne has good in vitro activity against Nocardia spp., further studies are necessary to confirm its clinical efficacy. 

The structure of the benzoate derivative 166 was established by X-ray analysis, confirming the selective oxidation of the sulfur atom at the 6-position of thieno[2,3- ]thiophene-2-sulfonamides. The activated double bond of the cyclic vinyl sulfone moiety readily underwent nucleophilic addition, which was exemplified by reaction of 165 with 4-methoxybenzylthiol in the presence of base to provide a mixture of 167 and 168 <1999JHC249>. 

Results showed a total of 2.8% of the samples (n 2972) to be inhibitor positive by the Delvotest SP test further examination identified 1.7% as -lactam antibiotics, and 1.1 % as sulfonamides and dapsone. The percentage of chloramphenicol suspicious samples determined by the Charm II test was amazingly high however, tests for confirmation were not available and contamination of the samples by residues of the chloramphenicol-based preservative azidiol could not be excluded with certainty. Low concentrations of streptomycins were also detected in 5.7% of the samples (n 1221), but the MRL was not exceeded. Macrolide and tetracycline residues were not found in significant levels. Model trials with commercially applied yoghurt cultures confirmed how important the compliance to MRLs can be to dairy industry compared to antibiotic-free milk, a pH of 5.0 was reached with a delay of 15 min in the case of contamination with cloxacillin 30 min in the case of penicillin, spiramycin, and tylosin and 45 min in the case of oxytetracycline contamination. 

In the following years, the survey for drug residues continued but focused on veterinary drugs commonly used in animal husbandry such as sulfonamides and tetracyclines, and on chloramphenicol. Screening was carried out using the Charm 11 test, while confirmation of positive results involved HPLC or GC-MS. The results obtained are summarized in Table 13.27. 

In addition, determination of a variety of sulfonamides has been carried out by coupling capillary LC with quadrupole MS through an ESP interface induced dissociation of the analytes by increasing the skimmer voltage could allow confirmation at the low-picomole range (110). LC-ESP-MS has been also found suitable for the determination of four coccidiostats in poultry products (111). 

If tlie identity of the detected drug residue is still unknown after these tests have been performed, a TLC-bioautography procedure is then applied to isolate and tentatively identify the residues (64, 72). This method is not quantitative and only gives direction to the analyst as to what determinative/confirmatory method of analysis should be used. Following this tentative identification, presumptive positives are then quantified and confirmed by validated physicochemical methods. A TLC method (73) is applied for analyzing presumptive sulfonamide residues, a GC-ECD method (74) followed by a GC-MS NCI method (75) for analyzing chloramphenicol, and LC/UV methods (76,77) for analyzing -lactams and tetracyclines. 

Excellent separation of sulfonamides can be achieved on conventional or fused silica capillary columns, the preferred type been the DB-5 capillary column. Following separation, electron-capture detector (254, 271) can be used for the determination of these drugs with good sensitivity and specificity. To confirm the presence of sulfonamides residues in edible animal products, mass spectrometric detectors are also frequently employed. Typical examples of such applications are those coupling gas chromatography with mass spectrometry via a chemical ionization (224, 254, 271) or electron impact (223, 256, 261) interface. 

Most promising literature methods, in terms of simplicity, selectivity, and sensitivity, for screening and even confirmation of sulfonamide residues in edible animal products appear to be those reported by Horie et al. (247), Simeonidou et al. (238), Boulaire et al. (66), and Abian et al. (221). 

The gene encoding 7,8-dihydropteroate synthase was cloned from P falciparum and found to encode a bifunctional enzyme that includes the pyrophosphokinase at the amino terminal of the protein. Discrepancies were observed in the sequences of 7,8-dihydropteroate synthase portion of the genes from sulfadoxine-sensitive versus sulfadoxine-resistant P falciparum, thus confirming that this enzyme is the target for the antimalarial sulfonamide drugs. 

A claim in the patent literature33 that a benzisothiazoline can be produced by the reaction between an A-benzyl-su bstituted sulfonamide and trichloromethanesulfenyl chloride [Eq. (4)], if confirmed, would be of great importance in opening the way to the preparation of many benzisothiazolines, as the benzylamines required for the reaction are readily available. 

M. Rodriguez and D.B. Orescan, Confirmation and quantitation of selected sulfonylurea, imida-zolinone, and sulfonamide herbicides in surface water using electrospray LC/MS, Anal. Chem., 70, 2710-2717 (1998). 

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