Deposit, tetracycline

Deposition of tetracyclines in bone tissue has been demonstrated in animals (147) and man (148). However, whereas osseous tissue in adult patients treated with tetracycline has shown deposits only in areas of repair or remodeUing, children s bones contain extensive areas of deposition. Tetracycline deposition in bone has been reported to have an effect on longitudinal bone growth (149). In experimental tissue cultures, osteogenesis was impaired by tetracyclines in concentrations similar to serum concentrations that are associated with a therapeutic effect (that is 1 pg/ml) (150). The deposition of tetracyclines in human bone begins in utero as early as in the first trimester of pregnancy (148). With regular tissue turnover, the deposits disappear. 

Nail deposition Tetracycline [45] Qofazimine [46] Wood s lamp light microscopy... 

Chelation to calcium, which is deposited in growing hones and teeth (e.g., tetracyclines in young children). 

The injection of tetracycline either before or simultaneously with injection of thorium-228 markedly reduced the deposition of thorium-228 in rat bone to about 60% of control values (Taylor et al. 

Taylor DM, Chipperfield AR, James AC. 1971. Effects of tetracycline on the deposition of plutonium and related elements in rat bone. Health Phys 21 197-204. 

Bone. Although bone is a relatively inert tissue, it can accumulate such substances as tetracyclines, lead, strontium, and the antitumor agent cisplatin. These substances may accumulate in bone by absorption onto the bone crystal surface and eventually be incorporated into the crystal lattice. Tetracycline deposition during odontogenesis may lead to a permanent yellow-brown discoloration of teeth, dysplasia, and poor bone development. Lead can substitute for calcium in the bone crystal lattice, resulting in bone brittleness. Bone may become a reservoir for the slow release of toxic substances, such as lead and cisplatin. 

The oral dosage for rapidly excreted tetracyclines, equivalent to tetracycline hydrochloride, is 0.25-0.5 g four times daily for adults and 20-40 mg/kg/d for children (8 years of age and older). For severe systemic infections, the higher dosage is indicated, at least for the first few days. The daily dose is 600 mg for demeclocycline or methacycline, 100 mg once or twice daily for doxycycline, and 100 mg twice daily for minocycline. Doxycycline is the oral tetracycline of choice because it can be given as a once-daily dose and its absorption is not significantly affected by food. All tetracyclines chelate with metals, and none should be orally administered with milk, antacids, or ferrous sulfate. To avoid deposition in growing bones or teeth, tetracyclines should be avoided in pregnant women and children less than 8 years of age. 

Tetracycline Prevents bacterial protein synthesis by binding to the 30S ribosomal subunit Bacteriostatic activity against susceptible bacteria Infections caused by mycoplasma, chlamydiae, rickettsiae, some spirochetes malaria H pylori acne Oral mixed clearance (half-life 8 h) dosed every 6 h divalent cations impair oral absorption Toxicity Gastrointestinal upset, hepatotoxicity, photosensitivity, deposition in bone and teeth... 

Correct answer = A. Most urinary tract infections are due to E. coii and can usually be treated with cotrimoxazole. However, this patient is near term and the sulfa in the cotrimoxazole might put the infant at risk due to kernicterus. Thus, the first generation cephalosporin, cefadroxil, is appropriate since it would be effective orally against penicillinase producing E. coii. Ceftriaxone, while it would be effective, would have to be administered parenterally. Penicillin V is not effective against E. coii. Tetracycline deposits in teeth and skeleton of the fetus and is contraindicated. 

Correct choice = A. Widespread resistance to tetracycline limits the clinical uses of this drug. Deposition of tetracycline in calcifying tissues of the fetus and growing children can occur. The drug has the potential for causing hepatic toxicity in the mother. Dairy foods in the diet decrease absorption because of the formation of nonabsorbable chelates of tetracycline with calcium ions. 

Correct choice = E. Only tetracycline is deposited in bone and thus is contraindicated in children under age 8. Ciprofloxacin damages developing articular cartilage in young experimental animals, which is why it is contraindicated In children under 18 years of age. All the other statements pertain to both antibiotics. 

Tetracycline and its derivative, minocycline, are used for control of acne vulgaris. Conjunctival deposits similar to those seen in epinephrine-treated glaucoma patients have been observed in patients treated orally with these compounds. Dosages ranged from 250 to 1,500 mg daily of tetracycline and at least 100 mg daily of minocycline. 

Anthony JR. Effect on deciduous and permanent teeth of tetracycline deposition in utero. Postgrad Med 1970 48(4) 165-8. 

The complexing of tetracyclines with calcium poses a problem in paediatric medicine. Discoloration of teeth results from the formation of a coloured complex with the calcium in the teeth the deposition of drug in the hones of growing hahies can lead to problems in bone formation. Table 10.4 reveals that there is no correlation between the binding capacity of a tetracycline with iron and that with calcium, suggesting different modes of complexation. The in vitro data are simpler to interpret the semm levels are the... 

Coincident with this new technique for procurement of human bone biopsies was the development of quantitive methods of bone analysis.12 These methods include histochemical analysis of both decalcified and unde-calcified42 48 bone sections, microradiography,44 tetracycline labeling45 and autoradiography.42 The latter two techniques require administration of a tetracycline antibiotic or isotopic tracer prior to procurement of the biopsy. Undecalcified thin sections, prepared with the use of a Jung microtome after the bone core is fixed, dehydrated and embedded in methacrylate,45 are analyzed by intersect and point count methods46 47 which permit three-dimensional assessment.48 49 Tetracycline antibiotics deposit in vivo in sites of bone formation constituting markers which can be studied in undecalcified sections by fluorescence microscopy.45 47 This represents the safest and best tissue time marker for microscopic measurement of bone formation dynamics. 

Tetracyclines bind to calcium and then become deposited in bone, causing damage to developing bone and teeth. Intravenous administration of tetracyclines has been observed to cause venous thrombosis. 

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