Aquaretics Flashcards
1
Q
Site of axn?
A
The collecting ducts
2
Q
MOA for Vaptans?
A
- Block ADH from binding to its receptor on the interstitial side –> ↓ H2O reabsorption in the CD through aquaporin channels
- Affinity for receptor subtypes V1A and V2
- ↓ plasma volume & ↑ plasma osmolality, primarily d/t to an ↑ in plasma [sodium]
3
Q
Which drugs are considered vaptans?
A
Conivaptan & Tolvaptan
4
Q
Effects of conivaptan?
A
- Promotes the excretion of free water without the loss of serum electrolytes
- leads to net fluid loss –> ↑ urine output, ↓ Uosm, ↑ Posm, restoration of nml plasma [Na+]
5
Q
Clinical applications of conivaptan?
A
- Trx of euvolemic and hypervolemic hyponatremia in pts who are hospitalized, symptomatic, and not responsive to fluid restriction
- ADPKD
- Monitor neuro status & plasma sodium closely –> too rapid serum sodium correction (>12 mEq/L/day) can lead to seizures, osmotic demyelination, coma, or death
6
Q
Pks of conivaptan?
A
- Administered IV
- Substrate of CYP3A4, concern w/ inducers and inhibitors
- water loss can concentrate other electrolytes or drugs to toxic range
- t1/2: eliminated primarily in feces as metabolites; 5.3-8.1 hrs
7
Q
Toxicities of conivaptan?
A
- Orthostatic hypotension, fatigue, thirst, polyuria, bedwetting
8
Q
Tolvaptan?
A
- Selective V2 R antagonist administered PO; initiate and reinitiate tolvaptan in pts only in hospital where plasma sodium can be closely monitored; must use for less than 30 days for hyponatremia, longer use –> potentially fatal hepatotoxicity
- Used to slow progression of adults polycystic kidney dz (must monitor liver)
- Effx ↑ to peak at ~ 4 hrs, effx last 4-8 hrs
