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Demeclocycline |
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Demeclocycline
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| Systematic (IUPAC) name | |
| 2-(amino-hydroxy-methylidene)- 7-chloro-4-dimethylamino- 6,10,11,12a-tetrahydroxy-4, 4a,5,5a,6,12a- hexahydrotetracene-1,3,12-trione | |
| Identifiers | |
| CAS number | 64-73-3 (HCl) |
| ATC code | D06 J01 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C21H21ClN2O8 |
| Mol. mass | 464.853 g/mol |
| Pharmacokinetic data | |
| Bioavailability | 60–80% |
| Protein binding | 41–50% |
| Metabolism | Hepatic |
| Half life | 10–17 hours |
| Excretion | Renal |
| Therapeutic considerations | |
| Pregnancy cat. |
D(US) |
| Legal status |
℞ Prescription only |
| Routes | Oral |
Demeclocycline (marketed as Declomycin, Declostatin and Ledermycin) is a tetracycline antibiotic officially indicated for the treatment of various types of bacterial infections. It is no longer used routinely as an antibacterial, however, but is widely used (though off-label in many countries) in the treatment of hyponatremia (low blood sodium concentration) due to the syndrome of inappropriate antidiuretic hormone (SIADH) when fluid restriction alone has been ineffective.1 It is derived from the Streptomyces aureofaciens actinomycete strain.
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Its use as an antibiotic is particularly in Lyme disease, acne and bronchitis. Resistance is gradually becoming more common, and demeclocycline is now rarely used for infections.
The use in SIADH actually relies on a side effect; demeclocycline induces nephrogenic diabetes insipidus (dehydration due to the inability to concentrate urine).1 The use of demeclocycline in SIADH was first reported in 1975,2 and, in 1978, a larger study found it to be more effective and better tolerated than lithium carbonate, the only available treatment at the time.3 Demeclocycline has since been the drug of choice for treating SIADH, although it may be superseded as vasopressin receptor antagonists such as tolvaptan become available.3
As other tetracyclines, demeclocycline is contraindicated in children and pregnant or nursing women. All members of this class interfere with bone development and may discolour teeth.4
These are similar to those of other tetracyclines. Skin reactions with sunlight have been reported.3 Demeclocycline is unique in that it is the only tetracycline known to cause nephrogenic diabetes insipidus.
Tetracyclines bind to cations such as calcium, iron (when given orally), and magnesium, rendering them insoluble and inabsorbable for the GI tract. Demeclocycline should not be taken with food (particularly milk and other dairy products) or antacids.4
As with related tetracycline antibiotics, demeclocycline acts by binding to the 30S- and 50S-RNA, which impairs protein synthesis by bacteria. It is therefore bacteriostatic (it impairs bacterial growth but does not kill bacteria directly).
It is not completely understood why demeclocycline impairs the action of antidiuretic hormone, but it is thought that it blocks the binding of the hormone to its receptor.5
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