(1997; 132 pages) [French] [Spanish]
Capsule or tablet, 250 mg of tetracycline hydrochloride
Tetracycline is a broad-spectrum antibiotic derived from a species of Streptomyces. It induces bacteriostasis by inhibiting protein synthesis, and is selectively concentrated in susceptible organisms.
Absorption of tetracycline from the gastrointestinal tract is always incomplete and can be further impaired by alkaline substances and chelating agents and, particularly, by milk and milk products, and by aluminium, calcium, magnesium and iron salts.
Peak plasma concentrations occur within 4 hours and decay with a half-life of about 8 hours. Excretion is primarily effected by glomerular filtration into the urine. Enterohepatic circulation gives rise to high concentrations in the liver and bile.
Tetracycline crosses the placenta and is excreted in the breast milk.
Treatment of moderate to severe acne.
Dosage and administration
Tetracycline should be given on an empty stomach, either 1 hour before or 1.5 hours after a meal in order to increase absorption.
Adults and children over 8 years: 250 mg orally four times daily for 4-8 weeks, followed by 250 mg twice daily until the lesions are cleared. In patients with severe, recalcitrant acne, the initial dose may need to be increased up to 2 g daily. Treatment may need to be continued for 6 months or more.
• Known hypersensitivity.
• Pre-existing severe hepatic or renal damage.
• Age under 8 years, since skeletal deposition can result in retardation of bone growth, hypoplasia of dental enamel and permanent brown discoloration of teeth.
Troublesome oesophagitis may be averted if the patient sits or stands up while swallowing capsules or tablets, and washes them down immediately with a glass of water. Capsules and tablets should not be taken with milk or with magnesium or aluminium salts since these impair the absorption of tetracycline.
Tetracycline should be withdrawn if infective diarrhoea occurs. Suprainfection of the bowel with resistant organisms can result in potentially fatal staphylococcal enteritis and pseudo-membranous colitis.
Time-expired tetracycline capsules or tablets should be discarded. Degraded tetracycline has been reported to induce renal dysfunction indistinguishable from the Fanconi syndrome and skin lesions similar to those of systemic lupus erythematosus.
Use in pregnancy
Tetracycline is contraindicated in pregnancy. It impairs skeletal calcification in the fetus and can result in abnormal osteogenesis and hypoplasia of dental enamel.
Gastrointestinal irritation is common, as is depletion of the normal bowel flora, permitting overgrowth of resistant organisms. Irritative diarrhoea should be differentiated from enteritis due to suprainfection, particularly with coagulase-positive staphylococci, and from pseudomembranous colitis due to Clostridium difficile. Overgrowth of resistant Candida species can also occur and vaginal candidosis is a common side-effect of tetracycline therapy.
Phototoxic reactions occasionally result in porphyria-like skin changes and pigmentation of the nails.
Pre-existing renal insufficiency may be aggravated. Acute renal failure and transient diabetes insipidus have been reported.
Transient depression of bone growth is largely reversible, but discoloration of teeth and enamel hypoplasia are permanent.
Hypersensitivity reactions are rare. Morbilliform rashes, urticaria, fixed drug eruptions, exfoliative dermatitis, cheilosis, glossitis, pruritus and vaginitis are described. Angioedema, anaphylaxis and pseudotumour cerebri have been reported.
The action of oral anticoagulants may be potentiated. Severe renal failure has been reported in patients who have received a halogenated anaesthetic agent while taking tetracyclines.
Capsules and tablets should be kept in well-closed containers, protected from light.