Tolvaptan (Samsca) Uses, Dosage, Adverse Effects

Tolvaptan (tol-vap’tan) Samsca

Classification: ELECTROLYTE & WATER BALANCE AGENT; DIURETIC; VASOPRESSIN ANTAGONIST

Therapeutic: VASOPRESSIN ANTAGONIST; DIURETIC

Prototype: Conivaptan

Pregnancy Category: C

AVAILABILITY

Tablet

ACTION & THERAPEUTIC EFFECT

Tolvaptan is a selective vasopressin V2-receptor antagonist, thus antagonizing the effect of vasopressin and causing an increase in urine water excretion, decrease in urine osmolality, and increase in serum sodium concentrations. Effectiveness is measured by increase in serum sodium level toward lower limit of normal, and/or decrease in sign and symptoms of hyponatremia.

USES

Treatment of hypervolemic and euvolemic hyponatremia.

CONTRAINDICATIONS

Rapid correction of serum sodium (e.g. greater than 12 mEq/L/24 h); cognitively impaired; serious neurologic symptoms; hypovolemic hyponatremia; hypertonic saline; concurrent administration with strong CYP3A inhibitors; lactation.

CAUTIOUS USE

Must be initiated or reinitiated in a hospital setting; cirrhosis; pregnancy (category C). Safe use in children younger than 18 y not established.

ROUTE & DOSAGE

Hyponatremia

Adult: PO Initially 15 mg once daily; may be adjusted up to 60 mg once daily

ADMINISTRATION

Oral

• Administer ONLY in setting where serum sodium can be closely monitored.
• Doses may be increased at 24 h intervals or greater.
• Do not administer if patient is unable to sense or respond to thirst.
• Store at 15°–30°C (59°–86°F).

ADVERSE EFFECTS (≥1%)

Body as a Whole: Asthenia, pyrexia, thirst. GI: Constipation, dry mouth, nausea. Metabolic: Anorexia, hyperglycemia. Urogenital: Pollakiuria, polyuria.

INTERACTIONS

Drug: Strong CYP3A INHIBITORS (e.g., clarithromycin, ketoconazole, itraconazole, telithromycin, saquinavir, nelfinavir, ritonavir, nefazodone) may increase tolvaptan levels. Moderate CYP3A INHIBITORS (e.g., erythromycin, fluconazole, aprepitant, diltiazem, verapamil) may increase tolvaptan levels.\ P-GLYCOPROTEIN INHIBITORS (e.g., cyclosporine) may require tolvaptan dosage reduction. CYP3A INDUCERS (e.g., rifabutin, rifapentine, rif- ampin, barbiturates, phenytoin, carbamazepine) decrease the levels of tolvaptan. Tolvaptan increases the levels of digoxin. BETA-BLOCKERS, ANGIOTENSIN RECEPTOR BLOCKERS, ANGIOTENSIN- CONVERTING ENZYME INHIBITORS and POTASSIUM-SPARING DIURETICS may cause hyperkalemia. Food: Administration with grapefruit juice may increase tolvaptan levels. Herbal: St. John’s wort may decrease the levels of tolvaptan.

PHARMACOKINETICS

Absorption: Approximately 40% absorbed. Peak: 2–4 h. Distribution: 99% plasma protein bound. Metabolism: In liver through CYP3A4. Elimination: Eliminated entirely by non-renal routes. Half-Life: 12 h.

NURSING IMPLICATIONS

Black Box Warning 

Tolvaptan has been associated with serious, sometime fatal, adverse events when hyponatremia is corrected too rapidly (e.g., more than 12 mEq/L per 24 h).

Assessment & Drug Effects

• Monitor vital signs frequently throughout therapy. Monitor ECG as warranted.
• Monitor weight and I&O closely as copious diuresis is expected.
• Fluid restriction should be avoided during the first 24 h of therapy.
• Monitor mental status throughout treatment. Report promptly changes in mental status (e.g., lethargy, confusion, disorientation, hallucinations, seizures).
• Report promptly symptoms of osmotic demyelination syndrome (ODS): Dysarthria, mutism, dysphagia, lethargy, affective changes, spasticity, seizures, or coma.
• Monitor digoxin levels closely with concurrent administration.
• Monitor lab tests: Baseline and frequent serum electrolytes especially serum sodium level; periodic blood glucose.

Patient & Family Education

• Continue to drink fluid in response to thirst until otherwise directed. Fluid restrictions are usually required after the first 24 h of therapy.
• Report promptly any of the following: Trouble speaking or swallowing, drowsiness, mood changes, confusion, involuntary body movements, or muscle weakness in arms or legs.

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Ditulis oleh Unknown pada tanggal Thursday, October 29, 2015