It is sometimes used to treat Spirochaetal infection,Clostridial wound infection and Anthrax in patients sensitive to Penicillin. Oxytetracycline is used to treat infections of the respiratory and urinary tracts, skin, ear, eye and Gonorrhoea although the use of Tetracyclines for such purposes has declined in recent years due to large increases in bacterial resistance to this class of drugs. The drug is particularly useful when Penicillins and/or Macrolides cannot be used due to allergy. It may be used to treat Legionnaire's Disease as a substitute for a Macrolide or Quinolone.

Oxytetracycline is especially valuable in treating Non-Specific-Urethritis, LGV, Lyme disease, Brucellosis, Cholera, Plague, Typhus, Relapsing Fever, Tulaeraemia and infections caused by Chlamydia, Mycoplasma and Rickettsia. Doxycycline is now preferred to Oxytetracycline for many of these indications because it has improved pharmacologic features.

The standard dose is 250-500mg six hourly by mouth. In particularly severe infections this dose may be increased accordingly. Occasionally, Oxytetracycline is given by intramuscular injection or topically in the form of creams, ophthalmic ointments or eye drops.

Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people that have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and Legionellosis. It is also used to treat outbreaks of chlamydia, syphilis, acne, and gonorrhea. In structure, this macrocyclic compound contains a 14-membered lactone ring with ten asymmetric centers and two sugars (L-cladinose and D-desoamine), making it a compound very difficult to produce via synthetic methods.

Side effects are mainly gastrointestinal and photosensitive allergic reactions common to the tetracycline antibiotics group.

Can also damage calcium rich organs such as teeth and bones although this is very rare, sometimes causes naval cavities to erode, quite common, the BNF suggests that because of this Tetracyclines should not be used to treat pregnant or lactating women and children under 12 except in certain conditions where it has been approved by a specialist because there are no obvious substitutes. Candidiasis (Thrush) is not uncommon following treatment with broad spectrum antibiotics.