The use in SIADH actually relies on a side effect; demeclocycline induces nephrogenic diabetes insipidus (dehydration due to the inability to concentrate urine). The use of demeclocycline in SIADH was first reported in 1975, 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. Demeclocycline has since been the drug of choice for treating SIADH, although it may be superseded as vasopressin receptor antagonists, such as tolvaptan, become available.
Contraindications[edit source | edit]
Like 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.
Side effects and interactions[edit source | edit]
These are similar to those of other tetracyclines. Skin reactions with sunlight have been reported. 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 gastrointestinal tract. Demeclocycline should not be taken with food (particularly milk and other dairy products) or antacids.
Mechanism of action[edit source | edit]
As with related tetracycline antibiotics, demeclocycline acts by binding to the 30S and 50S ribosomal subunits, which impairs protein synthesis by bacteria. It is 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 is thought to block the binding of the hormone from its receptor.
^Cherrill DA, Stote RM, Birge JR, Singer I (November 1975). "Demeclocycline treatment in the syndrome of inappropriate antidiuretic hormone secretion". Annals of Internal Medicine83 (5): 654–6. PMID173218.