tetracycline
Brand: Sumycin
Prototype Drug
Drug Class: tetracycline antibiotic
Drug Family: antibiotic
Subclass: prototypical tetracycline
Organ Systems: infectious-disease
Mechanism of Action
Reversibly binds 30S ribosomal subunit, blocking aminoacyl-tRNA binding; bacteriostatic. Prototype tetracycline with broad spectrum including atypical bacteria, chlamydiae, rickettsiae, and some protozoa.
30S ribosomal subunit
Indications
- Rocky Mountain spotted fever (Rickettsia)
- chlamydial infections
- Lyme disease (alternative to doxycycline)
- H. pylori eradication (quadruple therapy)
- acne vulgaris (oral)
- cholera
- brucellosis
Contraindications
- tetracycline hypersensitivity
- pregnancy
- children <8 years
- renal impairment (relative — avoid)
Adverse Effects
Common
- GI upset (most common with this class)
- photosensitivity
- esophageal irritation
Serious
- hepatotoxicity (high doses)
- pseudotumor cerebri
- permanent tooth discoloration (children)
- renal azotemia (anti-anabolic effect)
Pharmacokinetics (ADME)
| Absorption | 75–80%; significantly reduced by food, dairy, antacids, and divalent cations |
| Distribution | widely distributed; bone and dental deposition |
| Metabolism | not significantly metabolized |
| Excretion | renal (40–50%) and biliary (significant enterohepatic recirculation) |
| Half-life | 6–11 hours |
| Onset | 1–3 hours |
| Peak | 2–4 hours |
| Duration | 6–12 hours |
| Protein Binding | 65% |
| Vd | moderate-large |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| dairy products/antacids/iron/calcium/magnesium | chelation by divalent/trivalent cations dramatically reduces oral absorption | major |
| warfarin | gut flora suppression may potentiate anticoagulation | moderate |
| penicillins | bacteriostatic effect antagonizes the bactericidal activity of penicillins | moderate |
Nursing Considerations
- Administer on an empty stomach (1 hour before or 2 hours after meals); absolutely avoid concurrent dairy, antacids, calcium supplements, and iron — chelation can reduce absorption by >90%.
- Patient should take each dose with a full glass of water and avoid lying down for 30 minutes to prevent esophageal ulceration.
- Renal dose adjustment required; avoid use in patients with significant renal impairment as tetracycline has an anti-anabolic effect that worsens azotemia.
- Do not administer to pregnant women or children under 8 years; document this contraindication in the patient's chart.
Clinical Pearls
- Tetracycline is the prototype of the class but has been largely superseded by doxycycline due to its more favorable PK (twice-daily vs four-times-daily dosing, less affected by food).
- Tetracyclines chelate calcium during tooth development and bone growth, depositing yellow-brown pigment and causing enamel hypoplasia in children and fetuses — an irreversible and preventable complication.
Safety Profile
Pregnancy contraindicated
Lactation avoid
Renal Adjustment Required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
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