Tetracycline are broad-spectrum antibiotics that are active against many species of bacteria including Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia psittaci, Chlamydia trachomatis, Neisseria gonorrhoeae, and many others. Although the general usefulness of this medicine has been reduced with the onset of bacterial resistance, tetracycline antbiotic still remains the treatment of choice for some infections.

Tetracycline Side Effects

All the tetracyclines are absorbed from the gastrointestinal tract. Their absorption is impaired by the ingestion of milk or milk products and the administration of aluminum hydroxide gels and calcium and magnesium salts. Tetracyclines are usually taken by mouth but in certain forms may be given intravenously. However, intramuscular injection of these agents causes considerable pain. All the tetracylines are removed from the blood by the liver where they are concentrated and passed, by the way of the bile, into the intestine. From there they are absorbed into the blood and excreted in the urine.

Six tetracyclines in order of decreasing level of activity:

  • Doxycycline
  • Methacycline
  • Chlortetracycline
  • Demethylchlortetracycline
  • Tetracycline
  • Oxytetracycline

Tetracycline is commonly used in the treatment of; infections of the respiratory tract, streptococcus pneumonia, sinuses, middle ear, urinary tract, intestines, and also gonorrhea, moderately severe acne and rosacea, anthrax infection, plaque, malaria elephantiasis, cholera, chlamydia, rickettsia, spirochetal infections. It is used in combination with other medications to treat Helicobacter pylori, the bacteria associated with ulcers of the stomach.

Possible side effects of tetracycline: Skin rashes, brown or black coating of the tongue, sore mouth, blurred vision, vaginitis, fever, abdominal distress, nausea, vomiting, diarrhea, sunburn, and liver injury.


  • Children receiving tetracyclines and babies born to women treated with these agents from midpregnancy on may develop brown discoloration of the teeth and possibly affect the growth of teeth and bones.
  • Tetracyclines may increase muscle weakness in myasthenia gravis and worsen systemic lupus.
  • It was believed that tetracycline antibiotic impair the effectiveness of many types of hormonal contraception.
  • Tetracycline may result in excessive "thinning" of the blood.
  • Exaggerated sunburn can occur with tetracyclines; therefore, sunlight should be minimized during treatment.
  • Increased intracranial pressure may result from the use of tetracyclines in young babies.
  • These drugs must be given with great care to any patient with impaired kidney and liver function.

Administration: Tetracycline should be taken with full glass of water, in an empty stomach either two hours after eating or one hour before eating. Dairy products are not recommended directly after taking the drug, because milk and antacid reduces the absorption of tetracyclines. For most infections, tetracycline is taken two to four times daily for 7 to 14 days. Remember to always follow the directions on your prescription and if there is anything you don’t understand always ask the doctor or pharmacist because it is very important to take tetracycline as directed.

Preparation: Capsules: 250mg, 500mg; Tablets: 250mg, 500mg; Syrup: 125 mg/teaspoon.

Storage: Capsules should be kept below 30°C (86°F).