Oxytetracycline: classic tetracycline antibiotic
Oxytetracycline is a classic broad-spectrum antibiotic from the tetracycline group. The substance was isolated from Streptomyces rimosus in 1949 and is therefore one of the oldest tetracyclines. In human medicine it has largely been replaced by doxycycline and minocycline, while in veterinary medicine and for selected topical applications it still retains importance.
Compared with doxycycline, oxytetracycline has a shorter half-life (6 to 12 hours) and is excreted predominantly via the kidneys. Its more pronounced binding to divalent cations also leads to clinically relevant interactions with calcium-, magnesium-, iron- and aluminium-containing substances.
Mechanism of action
Oxytetracycline binds reversibly to the 30S subunit of the bacterial ribosome. This blocks attachment of aminoacyl tRNA to the A site, halting protein synthesis. The action is bacteriostatic, meaning bacterial growth is inhibited and the immune system ultimately eliminates the pathogens.
Because the 30S subunit is structurally similar in bacteria and mitochondria, oxytetracycline can also impair mitochondrial protein synthesis to a small extent, which contributes to some side effects. Selective uptake into bacteria via active transport systems protects human cells from clinically relevant effects.
Resistance arises mainly through efflux pumps and ribosomal protection proteins (Tet M, Tet O). These are widespread, which is why the spectrum is narrower today than at market launch.
Indications
- Acne vulgaris (oral and topical): classic indication, increasingly abandoned in favour of doxycycline or minocycline
- Respiratory infections (bronchitis, atypical pneumonia): mycoplasma, chlamydia, rickettsia
- Genital and ophthalmic chlamydial infections: classic tetracycline indication
- Lyme borreliosis: reserve therapy in case of doxycycline intolerance
- Cholera: as an additional antibacterial measure in severe disease
- Brucellosis, tularaemia, plague: often in combination
- Topical eye ointment: for superficial bacterial conjunctivitis and trachoma
- Pleurodesis: off-label intrapleural use for recurrent pleural effusions
Dosing and administration
Adults orally: 250 to 500 mg four times daily. Children over 8 years: 25 to 50 mg per kg per day, divided into four single doses.
Topically: eye ointment 1 % three to four times daily, skin cream as individually prescribed.
Oral administration is on an empty stomach, at least 1 hour before or 2 hours after meals. Importantly: no dairy product or calcium-containing drink within the dosing window, as absorption is markedly reduced through complex formation. Take with plenty of liquid while sitting or standing, to avoid oesophageal ulcers.
Renal impairment: dose adjustment required, contraindicated in severe dysfunction. Doxycycline is the better alternative here, as it is predominantly eliminated hepatically.
Side effects
Common: gastrointestinal complaints (nausea, abdominal pain, diarrhoea, glossitis, stomatitis), photosensitisation, vaginal or oral candidiasis.
Uncommon: oesophagitis and oesophageal ulcers (with insufficient fluid intake), allergic reactions with rash, urticaria, dizziness, headache, pseudotumor cerebri (idiopathic intracranial hypertension).
Rare: pancreatitis, hepatotoxicity, anaphylaxis, haemolytic anaemia, thrombocytopenia, lupus-like reaction, Stevens Johnson syndrome, acute interstitial nephritis, antibiotic-associated colitis from Clostridioides difficile.
Characteristic effects of all tetracyclines:
- Permanent discoloration of teeth and bone when used in pregnancy, breastfeeding or in children under 8 years
- Marked photosensitisation with sunburn even after brief UV exposure
- Complex formation with calcium leads to poor absorption and potentially discoloured teeth if taken during tooth development
- Vestibular disturbances (dizziness) somewhat more common with minocycline than with oxytetracycline
Interactions
- Polyvalent cations (calcium, magnesium, iron, aluminium, zinc): drastic reduction in absorption, minimum interval 2 hours before or 4 hours after oxytetracycline
- Antacids and sucralfate: also form complexes, observe interval
- Coumarins (warfarin, phenprocoumon): potentiated effect via reduced gut-flora vitamin K synthesis and altered plasma protein binding, monitor INR
- Oral contraceptives: current data show no clinically relevant failure, although caution is still recommended in summaries of product characteristics
- Methotrexate: increased toxicity due to displacement from plasma protein binding
- Penicillins: theoretical antagonism since tetracyclines are bacteriostatic and penicillins bactericidal; avoid combination except in special cases
- Retinoids (isotretinoin): increased risk of pseudotumor cerebri, combination contraindicated
Special considerations
Pregnancy: contraindicated from week 16 of pregnancy due to deposition into fetal bone and teeth. Avoid in the first trimester as well, if possible.
Breastfeeding: not recommended due to passage into milk and possible interference with the infant's tooth development.
Children under 8 years: contraindicated because of discoloration of permanent teeth and potential bone growth disturbance.
Liver disease: caution, hepatotoxicity is possible.
Renal impairment: accumulation, dose adjustment or choose doxycycline instead.
UV protection: intensive sun protection during therapy and for several days afterwards is recommended.
Expiry date: tetracyclines can degrade into nephrotoxic products if their expiry date is exceeded or if stored improperly (Fanconi syndrome). Dispose of expired preparations consistently.
Related substances
- Tigecyclin, modern glycylcycline against multi-resistant pathogens
- Cefaclor, alternative broad-spectrum beta-lactam
- Azithromycin, macrolide alternative for atypical pathogens
- Ciprofloxacin, fluoroquinolone alternative
Frequently asked questions
Why are dairy products and mineral water problematic?
Tetracyclines form poorly soluble complexes with calcium, magnesium, iron and aluminium that are no longer absorbed. Dairy products, mineral water, iron preparations and antacids must be taken at least 2 hours before or 4 hours after oxytetracycline; otherwise the antibiotic works unreliably.
Why do I sunburn so easily on oxytetracycline?
Tetracyclines absorb UV light and generate reactive oxygen species in the skin. Even brief UV exposure is therefore enough to provoke sunburn-like reactions. During therapy and for a few days afterwards: consistent sun protection, avoid direct sun where possible, use mineral-filter sunscreen.
Why not in children under 8 years?
Tetracyclines deposit in bone and teeth and can cause permanent yellowish to brown discoloration during tooth formation. Disturbances of bone growth have also been documented. Children under 8 should receive tetracyclines only in exceptional cases.
Does oxytetracycline help with a cold or the flu?
No. Colds and flu are caused by viruses, against which antibiotics are ineffective. Oxytetracycline should only be used for proven or clinically likely bacterial infections. Unnecessary antibiotic use promotes resistance.
Sources
- BfArM Federal Institute for Drugs and Medical Devices
- EMA European Medicines Agency
- AWMF guidelines acne and respiratory infections
- Gelbe Liste oxytetracycline monograph
Legal notice and disclaimer
The information on this page is provided for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medicines should only be used after a doctor's prescription or pharmacy supply. All information is based on summaries of product characteristics and accepted scientific sources at the time of writing; the current SmPC of the manufacturer is always decisive. Sanoliste accepts no liability for completeness, timeliness or accuracy. In a medical emergency, dial the emergency number 112.