Tetracycline is a broad-spectrum antibiotic used in the treatment of both Gram-negative and Gram-positive organisms and infections due to mycoplasma, chlamydia, and rickettsia — for acne, chronic bronchitis, and treatment of gonorrhea and syphilis. Tetracycline is one of a number of agents in the class, all of which have similar antimicrobial spectra. In animals, studies of oral administration, the pertinent route of administration in humans, are limited. In mice, 5 mg of tetracycline given over gestation caused only questionable abortion, and in rats, dietary dosing of up to 200 mg throughout most of gestation did not result in any developmental toxicity. In humans, as confirmed by statements on the package label, tetracycline causes fluorescent deposition of a yellow or gray-brown stain in calcifying teeth and bones in fetuses, infants, and children over a long time interval. Tetracycline is a large polar molecule.