[Acute toxic action of combinations of antibiotics with isoniazid]

Acute toxicity of isoniazid combinations with rifampicin or various streptomycin salts was studied on 1237 noninbred mice. The toxic effect of the combinations of the drugs in different weight ratios was estimated with the method of graphic analysis of Leve and Muischnek. The experiments showed that rifampicin and streptomycin had no effect on isoniazid ability to induce spasms. The combination of isoniazid with rifampicin had an additive action with an insignificant decrease in the toxic effect. 1 : 2 was the most optimal ratio of the drugs. When the mixture of isoniazid and streptomycin was used in the same syringe, the toxicity increased. However, injection of these drugs alone with an interval of 1-2 minutes had a more favourable additive effect when used in an optimal ratio of 1 : 1.6.