Residues Depletion Study and Withdrawal Period Determination of Sulphadiazine and Trimethoprim Premix in Pigs

The emergence and spread of antibiotic resistant human pathogens have been directly linked to the use of antibiotics in livestock production. The purpose of this study was to detect and quantify the concentration of the residues of Sulphadiazine (SDZ) and Trimethoprim (TMP) in edible tissues of pigs and to determine the withdrawal period after oral administration of OPTIPRIME^® premix 40%, containing 66.7 g TMP and 333.3 g SDZ per kg to healthy pigs. The depletion profile of SDZ and TMP was studied in healthy pigs, after oral administration of 1.5 kg OPTIPRIME^® per ton of feeding stuff, for 5 consecutive days. A total of 22 pigs at age 65±2 days and from 27.1-33.0 kg were used. The experimental animals were divided into 4 groups (5 pigs per group), while 2 pigs acted as control animals. All medicated pigs were sacrificed 1, 4, 7 and 11 days after the last administration and muscle, fat, liver and kidney tissues were collected and analyzed using a validated liquid chromatography-mass spectrophotometry method. On the 1st day post medication (pm), SDZ was found in muscle and fat at higher concentrations than TMP, whereas higher concentrations of TMP were found in the liver, while both substances were found in high concentrations in kidney samples. On 4th day pm SDZ and TMP could not be quantified or detected in any tissue. On 7th day pm, both substances were found in quantifiable concentrations in 1 out of 4 kidney samples, while on 11th day pm, all observations were below the Limit of Quantification (LOQ) of the method. The results show that both substances deplete rapidly in all tissues. A withdrawal period of 5 days is justified for the commercial product OPTIPRIME^® 40% premix in pigs.