Tetracycline
A tetracycline used for acne, chlamydia and rickettsial infections, in H. pylori bismuth quadruple therapy and as an eye ointment.
Drug card
- Class
- Tetracycline
- How it works
- Binding the 30S ribosomal subunit so tRNA cannot bring in new amino acids
- Used for
- Acne (adjunct therapy)
- Chlamydia infections
- Rickettsial infections, such as spotted fevers and typhus
- H. pylori, with bismuth, metronidazole and omeprazole
- Known for
- Permanent tooth discoloration if given under age 8
- Photosensitivity (exaggerated sunburn)
- Esophagitis and esophageal ulcers
- Its name
- -cycline means a tetracycline antibiotic
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does tetracycline work?
Tetracycline is made semisynthetically from chlortetracycline, a product of Streptomyces aureofaciens. It binds the 30S subunit and stops aminoacyl-tRNA reaching the ribosome, and it is mainly bacteriostatic. In kidney failure it builds up, and its antianabolic effect raises blood urea.
Like other tetracyclines: Tetracyclines bind the bacterial 30S ribosomal subunit and stop aminoacyl-tRNA from docking on the mRNA-ribosome complex, so no further amino acids are added. They are mainly bacteriostatic and broad-spectrum, including Chlamydia, Rickettsia and Mycoplasma. They form stable calcium complexes in growing bone, and metal ions in antacids and iron block their absorption.
Uses
What is tetracycline used for?
- Acne (adjunct therapy)
- Chlamydia infections
- Rickettsial infections, such as spotted fevers and typhus
- H. pylori, with bismuth, metronidazole and omeprazole
- Trachoma and bacterial conjunctivitis (eye ointment)
- Atypical pneumonia (Mycoplasma)
Side effects
Side effects of tetracycline
- Permanent tooth discoloration if given under age 8Known for
- Photosensitivity (exaggerated sunburn)Known for
- Esophagitis and esophageal ulcersKnown forSerious
- Nausea, vomiting and stomach upset
- Diarrhea
- Loss of appetite
- Candida overgrowth in the anogenital area
- Rising urea and acidosis in kidney failureSerious
- Liver toxicity and liver failureSerious
- Raised pressure in the skull (pseudotumor cerebri)Serious
- Fixed drug eruption and exfoliative dermatitisSerious
- Hemolytic anemia and low plateletsSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Avoid in the second half of pregnancy and in children under 8: teeth stain permanently and bone growth slows.
- Kidney impairment: it accumulates, raising urea and the risk of liver toxicity, so doses are lowered.
- Antacids, calcium, magnesium, iron, zinc and sodium bicarbonate cut its absorption.
- It may make oral contraceptives less effective and can increase warfarin's effect.
Good to know: Like other bacteriostatic tetracyclines, it can blunt the killing action of penicillin, so the two are not given together.
Remember it
A way to remember it
TEETH
- T
- Tooth discoloration in children under 8
- E
- Esophageal ulcers if taken just before lying down
- E
- Exaggerated sunburn (photosensitivity)
- T
- Thrush from Candida overgrowth
- H
- High pressure in the skull (pseudotumor cerebri)
TEETH fits a class best known for staining developing teeth; tetracyclines also bind calcium wherever bone is forming.
Written for biofideX
Its name
-cycline means tetracycline antibiotic
Doxycycline, minocycline and tigecycline share it. Anthracycline anticancer drugs such as doxorubicin end in -rubicin instead.
- Every drug name stem
Its class
Tetracyclines
Other tetracyclines with a card:
Easily mixed up with aminoglycosides, macrolides and fluoroquinolones.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Tetracycline hydrochloride capsules: label (DailyMed)
- Tetracycline (NCI Thesaurus)
- Bismuth subcitrate potassium, metronidazole and tetracycline hydrochloride capsules: label (DailyMed)
- WHO Model List of Essential Medicines, 24th list (2025) (WHO)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antibiotics: protein synthesis
Tetracycline is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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