Doxycycline, which is used orally, resembles other tetracyclines in its spectrum of in vitro antibacterial activity and clinical range of effectiveness; however, smaller and less frequent doses are required. Untoward reactions apparently are the same as those produced by other tetracyclines. It is excreted more slowly than other tetracyclines and should be used cautiously in patients with depressed renal function.
Evaluation of a New Antibacterial AgentDoxycycline Monohydrate and Doxycycline Hyclate (Vibramycin). JAMA. 1969;209(4):549–550. doi:10.1001/jama.1969.03160170045010