What are the side effects of tetracycline?

Tetracycline Side Effects

Tetracycline causes gastrointestinal disturbances (nausea, vomiting, diarrhea), permanent tooth discoloration in children under 8 years, photosensitivity, and rarely serious complications including esophageal ulceration and pseudotumor cerebri. 1, 2

Common Side Effects

Gastrointestinal Effects (Most Frequent)

• Anorexia, nausea, epigastric distress, vomiting, diarrhea are the most common tolerable adverse effects 1, 2
• Glossitis (tongue inflammation) and black hairy tongue
• Dysphagia (difficulty swallowing)
• Enterocolitis and inflammatory lesions with Candida overgrowth in the anogenital region 2
• Esophagitis and esophageal ulceration - particularly when capsules/tablets are taken immediately before bed 2, 3

Clinical Pitfall: Always instruct patients to take tetracycline with a full glass of water while sitting or standing, and avoid lying down immediately after administration to prevent esophageal injury 4.

Dermatologic Effects

• Photosensitivity - manifested by exaggerated sunburn reactions 1, 2
• Maculopapular and erythematous rashes 2
• Exfoliative dermatitis 1
• Onycholysis (nail separation) and nail discoloration 1, 2

Important: Advise patients to avoid direct sunlight or UV light exposure; discontinue at first evidence of skin erythema 2.

Dental Effects (Critical in Children)

• Permanent tooth discoloration (yellow-gray-brown) during tooth development 2, 5
• Enamel hypoplasia 1, 2
• This occurs when tetracyclines are used during the last half of pregnancy, infancy, and childhood up to age 8 years 2
• The discoloration is dose-related and more common with long-term use 2

Contraindication: Tetracycline should NOT be used in children <8 years of age unless other drugs are ineffective or contraindicated 1, 2.

Serious but Rare Side Effects

Intracranial Hypertension (Pseudotumor Cerebri)

• Presents with headache, blurred vision, diplopia, vision loss, and papilledema 2, 3
• Women of childbearing age who are overweight or have a history of intracranial hypertension are at greater risk 2
• Requires prompt ophthalmologic evaluation if visual disturbances occur 2
• Intracranial pressure can remain elevated for weeks after drug cessation 2

Hepatotoxicity

• Hepatotoxicity and liver failure have been observed 1, 2
• Higher risk in patients with renal impairment receiving tetracycline 2

Renal Effects

• Dose-related increase in blood urea nitrogen (BUN) 1, 2
• Can cause azotemia, hyperphosphatemia, and acidosis in patients with significantly impaired renal function 2

Hematologic Effects

• Hemolytic anemia 1, 2
• Thrombocytopenia, thrombocytopenic purpura 1, 2
• Neutropenia and eosinophilia 1, 2

Hypersensitivity Reactions

• Urticaria, angioneurotic edema, anaphylaxis 1, 2
• Anaphylactoid purpura, pericarditis 1, 2
• Exacerbation of systemic lupus erythematosus 1, 2
• Serum sickness-like reactions (fever, rash, arthralgia) 1, 2

Clostridium difficile-Associated Diarrhea (CDAD)

• Can range from mild diarrhea to fatal colitis 2
• Must be considered in all patients with diarrhea following tetracycline use 2
• Has been reported up to 2 months after antibiotic administration 2

Special Population Considerations

Pregnancy (Category D)

• Contraindicated in pregnancy due to risks of:
  • Malformation of teeth and bones in the fetus 6
  • Hepatotoxicity and pancreatitis in the mother 6
  • Retardation of skeletal development 2
• May be warranted only in life-threatening situations 6, 2

Nursing Mothers

• Distributed into breast milk 1
• Discontinue nursing or the drug 1, 2

Pediatric Use

• Should NOT be used in children <8 years unless absolutely necessary 1, 2
• Risk of permanent tooth discoloration and enamel hypoplasia 2
• Decreased fibula growth rate observed in premature infants 2

Drug Interactions

• Antacids (aluminum, calcium, magnesium-containing) - reduce absorption 1
• Oral anticoagulants - enhanced anticoagulant effect 1
• Hormonal contraceptives - reduced contraceptive efficacy 1
• Methoxyflurane - increased risk of renal toxicity 1
• Penicillins - antagonistic antibacterial effect 1

Monitoring Requirements for Long-Term Therapy

• Periodic laboratory evaluation of hematopoietic, renal, and hepatic function 2
• Serum level determinations if therapy is prolonged, especially with renal impairment 2
• Complete blood count monitoring if used long-term 1

Withdrawal Rates

A 2024 meta-analysis found that withdrawal rates due to adverse events were significantly higher with tetracyclines compared to placebo, though serious adverse events were rare 7. The most common reasons for discontinuation were gastrointestinal disturbances 7.