Tetracycline hydrochloride (NCI-c55561) is the hydrochloride salt of the tetracycline, a broad-spectrum naphthacene antibiotic produced semisynthetically from chlortetracycline, an antibiotic isolated from the bacterium Streptomyces aureofaciens. In bacteria, tetracycline blocks binding of aminoacyl-tRNA to the mRNA-ribosome complex, thereby inhibiting protein synthesis and bacterial cell growth. Because naturally, fluorescing tetracycline binds to a newly formed bone at the bone/osteoid interface, tetracycline-labeling of bone and fluorescence microscopy may be used to perform bone histomorphometry.

Tetracycline hydrochloride 是具有广谱性的化合物，能对抗多种革兰氏菌、非典型微生物如衣原体、支原体、立克次体和原虫寄生虫。Tetracycline hydrochloride 通过阻止氨酰tRNA与细菌核糖体的结合，抑制细菌蛋白质的合成。Tetracycline hydrochloride 通过OmpF和OmpC孔蛋白通道进入革兰氏阴性肠杆菌的外膜以带正电的阳离子（可能为镁）-Tetracycline hydrochloride 配位复合物形式[1]。

Tetracycline hydrochloride 被应用于治疗家禽、牛、羊和猪的感染。Tetracycline hydrochloride 还可用于促进生长或增强生长效果。在水产养殖中，Tetracycline hydrochloride 用于控制三文鱼、鲶鱼和龙虾的感染[2]。