Pregnancy category AU: D
Routes of administration-By mouth
Pharmacokinetic data
Bioavailability 80%
Metabolism Not metabolized
Elimination half-life 8–11 hours, 57–108 hours with kidney impairment.
Excretion Urine (>60%), feces
Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections including: acne, cholera, brucellosis, plague, malaria, and syphilis.
Common side effects include vomiting, diarrhea, rash, and loss of appetite, and other side effects include poor tooth development if used by children less than eight years of age, kidney problems, and sunburning easily.
Use during pregnancy may harm the baby.
It works by inhibiting protein synthesis in bacteria.
Tetracycline was originally made from bacteria of the genus Streptomyces.
Tetracyclines have a broad spectrum of antibiotic action, anspossess some level of bacteriostatic activity against almost all medically relevant aerobic and anaerobic bacterial genera, both Gram-positive and Gram-negative, with a few exceptions, such as Pseudomonas aeruginosa and Proteus spp., which display intrinsic resistance.
Acquired resistance has proliferated in many pathogenic organisms and greatly eroded the versatility of this group of antibiotics.
Resistance amongst Staphylococcus spp., Streptococcus spp., Neisseria gonorrhoeae, anaerobes, members of the Enterobacteriaceae, and several other previously sensitive organisms is common.
Tetracyclines remain especially useful in the management of infections by certain obligately intracellular bacterial pathogens such as Chlamydia, Mycoplasma, and Rickettsia.
Tetracyclines are also of value in spirochaetal infections, such as syphilis, and Lyme disease.
Certain rare or exotic infections, including anthrax, plague, and brucellosis, are also susceptible to tetracyclines.
Tetracycline is first-line therapy for Rocky Mountain spotted fever (Rickettsia), Lyme disease (B. burgdorferi), Q fever (Coxiella), psittacosis, Mycoplasma pneumoniae, and nasal carriage of meningococci.
Tetracycline may be used to treat peptic ulcers caused by bacterial infections, relying on disrupting protein translation in bacteria, thereby damaging the ability of microbes to grow and repair.
The following list presents MIC susceptibility data for some medically significant microorganisms:
The tetracyclines also have activity against certain eukaryotic parasites, amoeba, malaria (a plasmodium), and balantidiasis.
Since tetracycline is absorbed into bone, it is used as a marker of bone growth for biopsies in humans.
Tetracycline can discolor permanent teeth from prenatal period through childhood and adulthood.
Children receiving long- or short-term therapy with a tetracycline or glycylcycline may develop permanent brown discoloration of the teeth.
Tetracycline can be inactivated by calcium ions, so are not to be taken with milk, yogurt, and other dairy products
Uptake can also be inactivated by aluminium, iron, and zinc ions, not to be taken at the same time as some common antacids and over-the-counter heartburn medicines.
It can cause skin photosensitivity, so exposure to the sun or intense light is not recommended.
It can cause drug-induced lupus, and hepatitis.
It can cause microvesicular fatty liver, tinnitus, epigastric pain, interfere with methotrexate by displacing it from the various protein-binding site, cause breathing complications, as well as anaphylactic shock, in some individuals.
It can affect bone growth of the fetus, so should be avoided during pregnancy.
Fanconi syndrome may result from ingesting expired tetracyclines.
Caution should be exercised in long-term use when breastfeeding.
Short-term use is safe; bioavailability in milk is low to nil.
Cases of Stevens–Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme associated with doxycycline use have been reported, but a causative role has not been established.
Tetracycline inhibits protein synthesis by blocking the attachment of charged tRNA at the P site peptide chain.
It prevents the formation of a peptide chain.
Cells are not vulnerable to the effect of tetracycline as these cells contain no 30S ribosomal subunits so do not accumulate the drug, and accounts for the relatively small off-site effect of tetracycline on human cells.
Bacteria usually acquire resistance to tetracycline from transfer of a gene that either encodes an efflux pump or a ribosomal protection protein.
Efflux pumps actively eject tetracycline from the cell, preventing the build up of an inhibitory concentration of tetracycline in the cytoplasm.
Ribosomal protection proteins interact with the ribosome and dislodge tetracycline from the ribosome, allowing for translation to continue.
Tetracycline has a high affinity for calcium and is incorporated into bones during the active mineralization of hydroxyapatite.
When incorporated into bones, tetracycline can be identified using ultraviolet light.