Educational use only. Drug cards are AI-assisted study material for NCLEX preparation.
Mechanism of action
Bind the 30S ribosomal subunit, blocking aminoacyl-tRNA from binding the A site and inhibiting bacterial protein synthesis. Bacteriostatic with broad-spectrum activity including atypical organisms. Used for community-acquired pneumonia (atypical coverage), tick-borne illnesses (Rocky Mountain spotted fever, Lyme), chlamydial infections, acne, MRSA skin infections (doxycycline), and malaria prophylaxis.
Adverse effects
Life-threatening / NCLEX-tested
- Severe phototoxicity / sunburn — even brief sun exposure can blister
- Tooth discoloration and enamel hypoplasia in children < 8 years; staining of permanent teeth — DO NOT use in pregnancy or under 8 (with the partial exception of doxycycline in tick-borne illness, which is short-course and society-endorsed)
- Hepatotoxicity, especially with high IV doses in pregnancy
- Esophageal ulceration if swallowed without enough water or while supine
- Pseudotumor cerebri (idiopathic intracranial hypertension)
- Severe DRESS syndrome / SJS / TEN
- C. difficile colitis
Side effects
Common — what to teach
- GI upset, nausea, diarrhea
- Photosensitivity (burns easily)
- Vaginal yeast infection or thrush
- Vestibular effects (minocycline) — dizziness, vertigo
- Skin hyperpigmentation (minocycline, long-term use)
- Tinnitus
Food & drug interactions
Same divalent/trivalent cation problem as fluoroquinolones — calcium, magnesium, iron, zinc, aluminum, dairy, antacids, sucralfate bind tetracyclines and dramatically reduce absorption. SEPARATE BY 2 HOURS BEFORE OR 6 HOURS AFTER. Warfarin INR rises. Oral contraceptives may have reduced efficacy. Retinoids (isotretinoin) compound pseudotumor cerebri risk.
Nursing implications
Assessment, monitoring, patient teaching
- Counsel sun protection seriously — sunscreen, long sleeves, brimmed hat; avoid tanning beds; even brief direct sun can cause severe burns
- Take with a full glass of water and remain upright for at least 30 minutes after dosing to prevent esophageal ulceration — same rule as bisphosphonates and KCl tablets
- Take 2 hours before or 6 hours after dairy, antacids, calcium, iron, zinc
- Doxycycline can be taken with food; tetracycline must be on an empty stomach
- ABSOLUTE contraindication: pregnancy, breastfeeding, and children < 8 years for routine indications (tooth discoloration, bone deposition); doxycycline for short-course tick-borne illness in young children is the noted exception
- Watch for new severe headache, vision changes — pseudotumor cerebri
- Discard expired tetracyclines — degraded product can cause Fanconi-like syndrome
When to hold / contraindications
- Pregnancy (any trimester) for routine indications
- Children < 8 years for routine indications
- New severe headache or vision changes (pseudotumor cerebri suspicion)
- Severe rash, fever, mucosal involvement (SJS/TEN/DRESS)
- Severe hepatic impairment without dose review
- Active C. difficile infection until provider review
Memory anchor
Tetracyclines end in "-cycline." "Stains teeth and skips kids." Don't take with dairy/antacids; don't lie down after; sunscreen is mandatory.
Practice Tetracyclines questions
Test your recall on real NCLEX-style pharmacology questions — with full rationales and an AI Coach for the parts you miss.