2-(amino-hydroxy-methylidene)-4-dimethylamino-6,10,11,12a-tetrahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione

本品之抗菌範圍甚廣，為廣效抗生素。對於非耐酸性G(+)，G(-)細菌有效外，對阿巴米、立克次體及若干大形之濾過性病毒亦均有效。
對四環素敏感之較重要細菌有:鏈球菌、葡萄球菌(感受性菌種)、肺炎球菌、立克次體、克雷白氏菌、奈瑟氏菌。特別對四環素敏感之菌種為:流行性感冒嗜血桿菌、肺炎雙球菌、鏈球菌、白喉棒狀桿菌、大腸桿菌。
本品之性質較Oxytetracycline及Chlortetracycline為安定，副作用也較低。

Absorption
Tetracycline is adequately, but incompletely, absorbed from the GI tract.

Distribution
Tetracycline is about 65% bound to plasma proteins (short-acting). The protein binding for intermediate and long-acting analogs is usually greater. Penetration into most body fluids and tissues is excellent. Tetracycline is distributed in varying degrees in liver, bile, lung, kidney, prostate, urine, CSF, synovial fluid, mucosa of the maxillary sinus, brain, sputum, and bone. Tetracycline crosses the placenta and enters fetal circulation and amniotic fluid.

Metabolism
Tetracycline is concentrated by the liver in the bile.

Elimination
Tetracycline is excreted in both urine and feces at high concentrations in a biologically active form.

Antacids (containing aluminum, calcium, and magnesium), dairy products, food, iron salts
May decrease oral absorption of tetracycline.

Anticoagulants
The action of oral anticoagulants may be increased.

Methoxyflurane
Increased potential for nephrotoxicity exists; do not use together.

Oral contraceptives
May reduce effect of oral contraceptives.

Penicillins
May interfere with bactericidal action of penicillins.

1. 本抗生素作為口服或注射時，可能導致嚴重之肝及腎臟變壞，大量注射常能導致死亡，尤以孕婦及具肝腎疾病患者之長期治療為然，故在使用本劑前及使用期間內應作肝腎機能檢查，在發現對肝腎有副作用發生時當即停止使用或予適當治療則常可恢復正常。
2. 發現有過敏現象時，即應停止使用。
3. 治療期間同時觀察有否促成抗生素通有之無感受性菌生成(尤以內色念珠菌之感染)，如發現則酌量服用或借他法防止之。
4. 如患者腎臟機能有障礙時，僅以口服或非口服常用劑量，即可導致藥物體內蓄積量超過及可能發生肝臟中毒，在此狀況下，應使用比正常量為少之劑量，如治療需延長時，應注意測定血清中四環素濃度。