Demeclocycline hydrochloride

How it works

Demeclocycline induces a reversible, nephrogenic diabetes-insipidus-like state by reducing renal collecting-duct responsiveness to antidiuretic hormone, thereby promoting free-water excretion and raising serum sodium.

Prescribing in practice

• The most important safety point is dose-dependent, usually reversible nephrotoxicity, so renal function must be monitored and the drug avoided in significant renal or hepatic impairment.
• As a tetracycline it causes photosensitivity and is contraindicated in pregnancy, breastfeeding, and young children owing to dental staining and effects on bone.
• Absorption is reduced by calcium, antacids, iron, and dairy products, which should be separated from dosing.

Monitoring

Monitor serum sodium and renal function closely, titrating to avoid over-rapid sodium correction and detect rising urea or creatinine.

Counselling the patient

• Avoid taking this with milk, antacids, or iron supplements; separate them by a few hours.
• Use sun protection as your skin may burn more easily.
• Report reduced urine output or worsening tiredness, which may indicate kidney effects.

Evidence & guidelines

Demeclocycline is a recognised option for persistent SIADH in standard endocrinology references, used where fluid restriction alone is insufficient.