THE PHARMACOLOGY OF TERRAMYCIN

¹ Department of Pharmacology, Chas. Pfizer and Co., Inc., Brooklyn, N. Y.

1. The toxicity of Terramycin in experimental animals is relatively low.

2. The intravenous LD₅₀ of Terramycin hydrochloride in mice and rats was 192 and 280 mgm. per kgm., respectively. Sodium Terramycin exhibited a toxicity of a similar order in mice.

3. The oral and subcutaneous LD₅₀'s of Terramycin hydrochloride in mice were 7200 and 892 mgm. pet kgm., respectively and those of sodium Terramycin were 4410 and 270 mgm. per kgm., respectively.

4. Daily intramuscular injections of 40 mgm. of sodium Terramycin per kgm. were tolerated by two dogs for a period of more than 60 days. Oral administration of 80 to 400 mgm. per kgm. per day for a period of from 47 to 57 days was tolerated by a group of four dogs.

5. Two dogs received daily intramuscular injections of 160 and 240 mgm. of sodium Terramycin per kgm., respectively. The one receiving the lower dose died in eighteen days; the other died after six days. Both showed impaired renal and liver function one to four days before death. Histological examination showed clcudy swelling of liver and fatty metamorphosis of kidneys.

6. Daily oral administration of 80 to 160 mgm. of sodium Terramycin per kgm. for six to seven weeks did not affect the normal growth of rats and mice.

7. Aqueous solutions of Terramycin hydrochloride and sodium Terramycin were irritating when given intramuscularly or subcutaneously. Repeated intravenous injections of a 5 per cent solution of either salt at times may cause phlebitis.

8. Slow intravenous injection of a single dose of 100 mgm. of either sodium Terramycin or Terramycin hydrochloride per kgm. body weight to anesthetized cats and dogs caused no change in blood pressure.