ADH antagonist (post-receptor, not a vaptan)
ADH antagonist (post-receptor; not a vaptan)
- Blunts the collecting duct’s response to ADH downstream of V2 (↓ cAMP / aquaporin-2) — not receptor blockade
- ↑ renal free-water excretion
- ↑ serum Na⁺ in SIADH (syndrome of inappropriate ADH)
- Excessive effect → nephrogenic diabetes insipidus
Drugs with this mechanism (1)
- Demeclocycline — Tetracycline repurposed to treat SIADH via renal ADH antagonism.
Self-check
- Does the ADH antagonism shown here block V2 receptors directly?
No; it acts downstream on cAMP/aquaporin-2. - What can excessive collecting-duct ADH antagonism produce?
Nephrogenic diabetes insipidus.
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