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Hyponatremia is one of the most common electrolyte disorders associated with cancer1,2

In three large studies of cancer patients with hyponatremia, the rates of hyponatremia were3-6:

4.2%4

  • n = 6766 patients at admission
  • HN defined as a serum sodium level of <130 mEq/L

10.8%5

  • n = 6612 patients at admission
  • HN defined as a serum sodium level of <135 mEq/L

47%6

  • n = 3357 patients
    • 23% at admission
    • 24% acquired during hospitalization
  • HN defined as a serum sodium level <135 mEq/L

Not all of these patients will be appropriate for therapy with SAMSCA.

Hyponatremia is most often caused by SIADH in cancer patients1,7

  • SIADH is most commonly found in patients with small cell lung cancer (SCLC)3
  • SIADH has also been reported in patients with head and neck cancer3
  • SIADH in patients with cancer may be due to3:
    • Inappropriate secretion of vasopressin with malignancy
    • Agents commonly used in cancer treatment and palliative care

Certain drugs commonly used in patients with cancer are known to cause hyponatremia by inducing SIADH3

* Cisplatin may also cause hyponatremia by damaging renal tubes and interfering with sodium reabsorption.
Adapted from Castillo et al, Oncologist, 2012.3

* Cisplatin may also cause hyponatremia by damaging renal tubes and interfering with sodium reabsorption.
Adapted from Castillo et al, Oncologist, 2012.3

Fluid restriction is considered the standard of care for dilutional hyponatremia8,9

Fluid restriction addresses total body water imbalance8,9

  • In some patients, hyponatremia can resist correction with fluid restriction10

Fluid Restriction can be difficult in the oncology setting3

  • Some patients with hyponatremia in SIADH experience an exaggerated need to drink due to downward resetting of the osmotic threshold for thirst11

INDICATION and IMPORTANT SAFETY INFORMATION for SAMSCA® (tolvaptan)

INDICATION:

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

Important Limitations:

  • Patients requiring intervention to raise serum sodium urgently to prevent or to treat serious neurological symptoms should not be treated with SAMSCA
  • It has not been established that raising serum sodium with SAMSCA provides a symptomatic benefit to patients

IMPORTANT SAFETY INFORMATION:

SAMSCA should be initiated and re-initiated in patients only in a hospital where serum sodium can be monitored closely. Too-rapid correction of hyponatremia (e.g., >12 mEq/L/24 hours) can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death. In susceptible patients, including those with severe malnutrition, alcoholism or advanced liver disease, slower rates of correction may be advisable.

SAMSCA is contraindicated in the following conditions:

  • — Urgent need to raise serum sodium acutely
  • — Inability of the patient to sense or appropriately respond to thirst
  • — Hypovolemic hyponatremia
  • — Concomitant use of strong CYP 3A inhibitors
  • — Anuric patients
  • — Hypersensitivity (e.g. anaphylactic shock, rash generalized) to tolvaptan or its components
  • Too-rapid Correction of Serum Sodium Can Cause Serious Neurologic Sequelae: During initiation and after titration monitor patients to assess serum sodium concentrations and neurologic status. Subjects with SIADH or very low baseline serum sodium concentrations may be at greater risk for too-rapid correction of serum sodium. In patients receiving SAMSCA who develop too-rapid a rise in serum sodium, discontinue or interrupt treatment with SAMSCA and consider administration of hypotonic fluid. Fluid restriction during the first 24 hours with SAMSCA may increase the likelihood of overly-rapid correction of serum sodium, and should generally be avoided. Co-administration of diuretics also increases the risk of too-rapid correction of serum sodium and such patients should undergo close monitoring of serum sodium
  • Liver Injury: SAMSCA can cause serious and potentially fatal liver injury. In a placebo-controlled and open-label extension study of chronically administered tolvaptan in patients with autosomal dominant polycystic kidney disease (ADPKD), cases of serious liver injury attributed to tolvaptan were observed. Avoid use in patients with underlying liver disease, including cirrhosis, because the ability to recover may be impaired. Limit duration of therapy with SAMSCA to 30 days. SAMSCA is not approved for use in ADPKD
  • Dehydration and Hypovolemia: In patients who develop medically significant signs or symptoms of hypovolemia, discontinuation is recommended. Dehydration and hypovolemia can occur, especially in potentially volume-depleted patients receiving diuretics or those who are fluid restricted
  • Co-administration With Hypertonic Saline: Not recommended
  • Other Drugs Affecting Exposure to SAMSCA:
  • CYP 3A Inhibitors: Do not use with strong inhibitors of CYP 3A; avoid concomitant use with moderate CYP 3A inhibitors
  • CYP 3A Inducers: Avoid concomitant use with CYP 3A inducers. If co-administered, the dose of SAMSCA may need to be increased
  • P-gp Inhibitors: The dose of SAMSCA may have to be reduced if co-administered with P-gp inhibitors
  • Hyperkalemia or Drugs that Increase Serum Potassium: Monitor serum potassium levels in patients with a serum potassium >5 mEq/L and in patients receiving drugs known to increase serum potassium levels

Pregnancy and Nursing Mothers: SAMSCA should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Because many drugs are excreted into human milk and because of the potential for serious adverse reactions in nursing infants from SAMSCA, a decision should be made to discontinue nursing or SAMSCA, taking into consideration the importance of SAMSCA to the mother.

Adverse Reactions: The most common adverse reactions (SAMSCA incidence ≥5% more than placebo, respectively): thirst (16% vs 5%), dry mouth (13% vs 4%), asthenia (9% vs 4%), constipation (7% vs 2%), pollakiuria or polyuria (11% vs 3%) and hyperglycemia (6% vs 1%).

Gastrointestinal Bleeding in Patients with Cirrhosis: In patients with cirrhosis in the hyponatremia trials, GI bleeding was reported in 10% of tolvaptan-treated patients vs 2% for placebo.

To report SUSPECTED ADVERSE REACTIONS, contact Otsuka America Pharmaceutical, Inc. at 1-800-438-9927 or FDA at 1-800-FDA-1088 (www.fda.gov/medwatch).

Please see FULL PRESCRIBING INFORMATION, including BOXED WARNING.

References:

1
Onitilo AA, Kio E, Doi SAR. Tumor-related hyponatremia. Clin Med Res. 2007;5(4):228-237.
2
Sarhill N, Walsh D, Nelson K, Davis M. Evaluation and treatment of cancer-related fluid deficits: volume depletion and dehydration. Support Care Cancer. 2001;9(6):408-419.
3
Castillo JJ, Vincent M, Justice E. Diagnosis and management of hyponatremia in cancer patients. Oncologist. 2012;17(6):756-765.
4
Hampshire PA, Welch CA, McCrossan LA, Francis K, Harrison DA. Admission factors associated with hospital mortality in patients with haematological malignancy admitted to UK adult, general critical care units: a secondary analysis of the ICNARC Case Mix Programme Database. Crit Care. 2009;13(4):R137.
5
Waikar SS, Mount DB, Curhan GC. Mortality after hospitalization with mild, moderate, and severe hyponatremia. Am J Med. 2009;122(9):857-865.
6
Doshi SM, Shah P, Lei X, Lahoti A, Salahudeen AK. Hyponatremia in hospitalized cancer patients and its impact on clinical outcomes. Am J Kidney Dis. 2012;59(2):222-228.
7
Raftopoulos H. Diagnosis and management of hyponatremia in cancer patients. Support Care Cancer. 2007;15(12):1341-1347.
8
Douglas I. Hyponatremia: why it matters, how it presents, how we can manage it. Cleve Clin J Med. 2006;73(suppl 3):S4-S12.
9
Berl T. Treatment of the syndrome of inappropriate antidiuretic hormone secretion and the emergence of vasopressin antagonists for hyponatremic disorders. Nephrol Rounds. 2007;5(5):2-6. http://nephrologyrounds.org/crus/usneph0507.pdf. Accessed May 22, 2013.
10
Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013;126(10 suppl 1):S1-S4.
11
Smith D, Moore K, Torney W, Baylis PH, Thompson CJ. Downward resetting of the osmotic threshold for thirst in patients with SIADH. Am J Physiol Endocrinol Metab. 2004;287(5):E1019-E1023. doi: 10.1152/ajpendo.00033.24.