Studies on the Acute Toxicity of Chlortetracycline Hydrochloride, with Special Reference to the Effect of Heating on its Toxicity

Toxicity studies were made on chlortetracycline hydrochloride (CTC) in ddN mice, emphasis being placed on the effect of heating at 100°C for 30 minutes on its toxicity. 1) pH of CTC solutions in distilled water at the concentrations of 0.75% to 2.0%, suitable for assessing LD50 in mice, was in the range of 2.98 to 2.70. 2) pH of CTC buffer solutions consisting of 1/30M of KH2PO4 and Na2HPO4·2H2O at a ratio of 3 to 7, was 6.37 to 6.3 in the 0.75% and 1.0% solutions, and 2.77-3.96 in the 2.0% solution. 3) When injected intraperitoneally, both vehicles and heating exerted no significant changes on the LD50 value of CTC. 4) In the intravenous route, heating had no effect on the LD50 value of CTC in the acid solutions, and elevated its value remarkably in the buffered solutions. But LD50 values of CTC in the latter solutions before and after heating were far less than those in the acid solutions, indicating that the addition of buffer agents mentioned above intensified the toxicity of CTC.