Medicine & USMLE


Other Endocrine Pharm
  1. Thionamides (PTU vs Methimazole)
  2. ADH Antagonists (Conivaptan, Tolvaptan)
  3. Levothyroxine (T4) vs Liothyronine (T3)
  4. Demeclocycline
  5. Desmopressin
  6. Cinacalcet
  7. Sevelamer


Demeclocycline is a tetracycline drug that also functions as an ADH or vasopressin inhibitor. By blocking the effects of ADH binding, the drug can help treat the effects of having too much ADH in SIADH. However, taking too much demeclocycline may lead to a side effect of nephrogenic diabetes insipidus, in which there is too little ADH signaling at the kidney.

Key Points

  • Demeclocycline
    • Mechanism
      • ADH (vasopressin) antagonist
      • Member of tetracycline class of antibiotics
    • Indications
      • Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
        • Antagonism of ADH receptors reverses effects of overproduction of ADH (e.g. hyponatremia)
    • Adverse Effects
      • Diabetes insipidus (DI)
        • Resembles nephrogenic DI, with kidneys unresponsive to ADH signalling and increased free water loss (very dilute urine)
      • Photosensitivity
        • Related to tetracycline effects
      • Abnormalities of bone and teeth
        • Related to tetracycline effects