tolvaptan

(tol-vap-tan) tolvaptan,

Samsca

(trade name)

Classification

Therapeutic: electrolyte modifiers
Pharmacologic: vasopressin antagonists
Pregnancy Category: C

Indications

Treatment of significant hypervolemic and euvolemic hyponatremia (serum sodium <125 mEq/L or less marked symptomatic hyponatremia that has resisted correction by fluid restriction), including patients with heart failure and Syndrome of Inappropriate Antidiuretic Hormone (SIADH).

Action

Acts as a selective vasopressin V2-receptor antagonist, resulting in increased renal water excretion and increased serum sodium.

Therapeutic effects

Correction of hyponatremia.

Pharmacokinetics

Absorption: 40% absorbed following oral administration.Distribution: >99%.Metabolism and Excretion: Extensively metabolized primarily by the CYP3A4 enzyme system; no renal elimination.Half-life: 12 hr.

Time/action profile

ROUTE	ONSET	PEAK	DURATION
PO	within 8 hr	2–4 hr†	7 days

† Blood level

Contraindications/Precautions

Contraindicated in: Urgent need to acutely raise serum sodium;Patients who cannot appropriately sense/respond to thirst;Hypovolemic hyponatremia;Concurrent use of strong or moderate CYP3A inhibitors;Anuria;Liver disease Lactation: Avoid use.Use Cautiously in: Severe malnutrition, alcoholism or advanced liver disease (↑ risk of osmotic demyelination; correct electrolyte abnormalities at a slower rates);Cirrhosis (↑ risk of GI bleeding, use only when the need to treat outweighs risk); Geriatric: May have ↑ sensitivity to effects; Obstetric: Use only if the potential benefit justifies the potential risk to the fetus; Pediatric: Safety and effectiveness not established.

Adverse Reactions/Side Effects

Central nervous system

weakness (most frequent)

Gastrointestinal

hepatotoxicity (life-threatening)
constipation (most frequent)
dry mouth (most frequent)

Genitourinary

polyuria (most frequent)

Fluid and Electrolyte

thirst (most frequent)

Metabolic

hyperglycemia (most frequent)

Neurologic

osmotic demyelination

Interactions

Drug-Drug interaction

Strong inhibitors of the CYP3A enzyme system including ketoconazole, clarithromycin, itraconazole, telithromycin, saquinavir, nelfinavir, ritonavir, and nefazodone ↑ levels and may ↑ effects and risk of toxicity; concurrent use should be avoided.Moderate CYP 3A inhibitors including erythromycin, fluconazole, aprepitant, diltiazem, and verapamil may have a similar effect and should also be avoided.Inducers of the CYP3A enzyme system including rifampin can ↓ blood levels and effectiveness; dosage adjustments may be necessary.Levels and risk of toxicity are also ↑ P-gp inhibitors including cyclosporine ; dosage adjustments may be necessary.May ↑ digoxin levels; monitor carefully.May ↑ risk of hyperkalemia with angiotensin receptor blockers, ACE inhibitors, and potassium-sparing diuretics.Grapefruit juice ↑ levels and the risk of toxicity; avoid concurrent use.

Route/Dosage

Oral (Adults) 15 mg once daily initially; may be ↑ at intervals of at least one day to 30 mg once daily, up to a maximum of 60 mg once daily. Do not use for longer than 30 days.

Availability

Tablets: 15 mg, 30 mg

Nursing implications

Nursing assessment

Monitor neurologic status and assess for signs and symptoms of osmotic demyelination syndrome (trouble speaking, dysphagia, drowsiness, confusion, mood changes, involuntary movements, weakness, seizures), especially during initiation and after titration. If a rapid ↑ in sodium or symptoms occur, discontinue tolvaptan and consider administration of hypotonic fluid.
Monitor fluid balance. If hypovolemia occurs interrupt or discontinue tolvaptan and provide supportive care (monitor vital signs, balance fluid and electrolytes).
Monitor for signs and symptoms of liver injury (fatigue, anorexia, right upper abdominal discomfort, dark urine, jaundice) periodically during therapy. If symptoms occur, discontinue therapy.
Lab Test Considerations: Monitor serum sodium levels frequently during initiation and dose titration and periodically during therapy. Too rapid correction of hyponatremia (>12 mEq/L/24 hr) can cause osmotic demyelination syndrome.
- Monitor serum potassium in patients with serum potassium >5 mEq/L or taking medication known to ↑ potassium.

Potential Nursing Diagnoses

Risk for imbalanced fluid volume (Indications)

Implementation

Initiate and re-initiate therapy in a hospital.
- Avoid fluid restriction during first 24 hr of therapy.
Oral: Administer once daily without regard to meals.

Patient/Family Teaching

Instruct patient to take tolvaptan as directed. Avoid drinking grapefruit juice during therapy; may cause ↑ levels. Take missed doses as soon as remembered, but not if just before next dose; do not double doses. Do not stop and restart therapy. Restarting therapy may require hospitalization.
Inform patients they can continue fluid ingestion in response to thirst during therapy and should have water available to drink at all times during therapy. Following discontinuation of therapy, resume fluid restriction.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Advise patient to notify health care professional if signs of dehydration (vomiting, diarrhea, inability to drink normally, dizziness, feeling faint) or bleeding (vomiting bright red blood, dark blood clots, or coffee-ground-like material; black, tarry stools; bloody stools).
Advise female patients to notify health care professional if pregnancy is planned or suspected or if breast feeding.

Evaluation/Desired Outcomes

Normalization of serum sodium levels. Therapy should be limited to 30 days.

tolvaptan

A vasopressin receptor-2 antagonist approved by the FDA in 2009 for treating hyponatremia associated with congestive heart failure, cirrhosis, and syndrome of inappropriate antidiuretic hormone (SIADH).

tolvaptan

A selective oral antagonist of the vasopressin V2 receptor in the renal collecting tubule, used to treat low blood sodium levels (hyponatraemia) in patients with chronic heart failure and cirrhosis of the liver. Side effects include dry mouth, thirst and uncreased urinary output.