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Samsca Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 11/5/2015

Samsca (tolvaptan) is a vasopressin receptor antagonist, which increases the amount of urine you make, causing your body to get rid of extra water which helps to slowly increase to normal levels of salt (sodium) in the blood, used to treat hyponatremia (low levels of sodium in your blood) in people with heart failure, liver disease, and certain hormonal imbalances. Common side effects of Samsca include increased thirst or urination, dry mouth, loss of appetite, constipation, weakness, fruity breath odor, drowsiness, dry skin, nausea, or vomiting.

The usual starting dose for Samsca is 15 mg administered once daily without regard to meals. Increase the dose to 30 mg once daily, after at least 24 hours, to a maximum of 60 mg once daily, as needed to achieve the desired level of serum sodium. Samsca may interact with aprepitant, birth control pills, cyclosporine, digoxin, rifabutin, rifampin, rifapentine, St. John's wort, antibiotics, antidepressants, barbiturates, diuretics (water pills), heart or blood pressure medications, HIV or AIDS medicines, potassium supplements, or seizure medications. Tell your doctor all medications and supplements you use. During pregnancy, Samsca should be used only when prescribed. It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

Our Samsca (tolvaptan) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Samsca in Detail - Patient Information: Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Tell your caregivers at once if you have any of these signs that your hyponatremia is being reversed too quickly:

  • problems with speech or muscle control;
  • trouble swallowing;
  • trouble moving your arms and legs;
  • mood changes; and
  • seizure (convulsions).

Stop using tolvaptan and call your doctor at once if you have:

  • weakness or fainting;
  • black, bloody, or tarry stools;
  • coughing up blood or vomit that looks like coffee grounds;
  • nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • dehydration (feeling very thirsty or hot, being unable to urinate, heavy sweating, or hot and dry skin).

Common side effects may include:

  • dry mouth;
  • increased thirst or urination;
  • constipation; or
  • loss of appetite, fruity breath odor, drowsiness, dry skin, nausea, vomiting.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Samsca (Tolvaptan Tablets )

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Samsca Overview - Patient Information: Side Effects

SIDE EFFECTS: See also Warning section.

Thirst, dry mouth, loss of appetite, constipation, or weakness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Loss of too much body water (dehydration) can occur. The risk is increased if you have persistent vomiting or diarrhea, and cannot drink normally. Contact your doctor immediately if you notice any symptoms of dehydration, such as fast heartbeat or dizziness/lightheadedness.

People with severe liver disease (cirrhosis) may have increased risk of bleeding from the stomach or intestines while taking this medication. Tell your doctor immediately if you have any of the following symptoms: black/bloody stools, vomit that contains blood or looks like coffee grounds.

Tolvaptan may rarely cause serious (possibly fatal) liver disease. Get medical help right away if you have any symptoms of liver damage, including: dark urine, persistent nausea/vomiting/loss of appetite, stomach/abdominal pain, yellowing eyes/skin.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Samsca (Tolvaptan Tablets )

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Samsca FDA Prescribing Information: Side Effects
(Adverse Reactions)


Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reactions rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The adverse event information from clinical trials does, however, provide a basis for identifying the adverse events that appear to be related to drug use and for approximating rates.

In multiple-dose, placebo-controlled trials, 607 hyponatremic patients (serum sodium < 135 mEq/L) were treated with SAMSCA. The mean age of these patients was 62 years; 70% of patients were male and 82% were Caucasian. One hundred eighty nine (189) tolvaptan-treated patients had a serum sodium < 130 mEq/L, and 52 patients had a serum sodium < 125 mEq/L. Hyponatremia was attributed to cirrhosis in 17% of patients, heart failure in 68% and SIADH/other in 16%. Of these patients, 223 were treated with the recommended dose titration (15 mg titrated to 60 mg as needed to raise serum sodium).

Overall, over 4,000 patients have been treated with oral doses of tolvaptan in open-label or placebo-controlled clinical trials. Approximately 650 of these patients had hyponatremia; approximately 219 of these hyponatremic patients were treated with tolvaptan for 6 months or more.

The most common adverse reactions (incidence ≥ 5% more than placebo) seen in two 30-day, double-blind, placebo-controlled hyponatremia trials in which tolvaptan was administered in titrated doses (15 mg to 60 mg once daily) were thirst, dry mouth, asthenia, constipation, pollakiuria or polyuria and hyperglycemia. In these trials, 10% (23/223) of tolvaptan-treated patients discontinued treatment because of an adverse event, compared to 12% (26/220) of placebo-treated patients; no adverse reaction resulting in discontinuation of trial medication occurred at an incidence of > 1% in tolvaptan-treated patients.

Table 1 lists the adverse reactions reported in tolvaptan-treated patients with hyponatremia (serum sodium < 135 mEq/L) and at a rate at least 2% greater than placebo-treated patients in two 30-day, double-blind, placebo-controlled trials. In these studies, 223 patients were exposed to tolvaptan (starting dose 15 mg, titrated to 30 and 60 mg as needed to raise serum sodium). Adverse events resulting in death in these trials were 6% in tolvaptan-treated-patients and 6% in placebo-treated patients.

Table 1: Adverse Reactions ( > 2% more than placebo) in Tolvaptan-Treated Patients in Double-Blind, Placebo-Controlled Hyponatremia Trials

System Organ Class
MedDRA Preferred Term
Tolvaptan 15 mg/day-60 mg/day
(N = 223)
n (%)
(N = 220)
n (%)
Gastrointestinal Disorders
Dry mouth 28 (13) 9 (4)
Constipation 16 (7) 4 (2)
General Disorders and Administration Site Conditions
Thirsta 35 (16) 11 (5)
Asthenia 19 (9) 9 (4)
Pyrexia 9 (4) 2 (1)
Metabolism and Nutrition Disorders
Hyperglycemiab 14 (6) 2 (1)
Anorexiac 8 (4) 2 (1)
Renal and Urinary Disorders
Pollakiuria or polyuriad 25 (11) 7 (3)
The following terms are subsumed under the referenced ADR in Table 1:
bdiabetes mellitus;
cdecreased appetite;
durine output increased, micturition urgency, nocturia

In a subgroup of patients with hyponatremia (N = 475, serum sodium < 135 mEq/L) enrolled in a double-blind, placebo-controlled trial (mean duration of treatment was 9 months) of patients with worsening heart failure, the following adverse reactions occurred in tolvaptan-treated patients at a rate at least 2% greater than placebo: mortality (42% tolvaptan, 38% placebo), nausea (21% tolvaptan, 16% placebo), thirst (12% tolvaptan, 2% placebo), dry mouth (7% tolvaptan, 2% placebo) and polyuria or pollakiuria (4% tolvaptan, 1% placebo).

Gastrointestinal bleeding in patients with cirrhosis

In patients with cirrhosis treated with tolvaptan in the hyponatremia trials, gastrointestinal bleeding was reported in 6 out of 63 (10%) tolvaptan-treated patients and 1 out of 57 (2%) placebo treated patients.

The following adverse reactions occurred in < 2% of hyponatremic patients treated with SAMSCA and at a rate greater than placebo in double-blind placebo-controlled trials (N = 607 tolvaptan; N = 518 placebo) or in < 2% of patients in an uncontrolled trial of patients with hyponatremia (N = 111) and are not mentioned elsewhere in the label.

Blood and Lymphatic System Disorders: Disseminated intravascular coagulation

Cardiac Disorders: Intracardiac thrombus, ventricular fibrillation

Investigations: Prothrombin time prolonged

Gastrointestinal Disorders: Ischemic colitis

Metabolism and Nutrition Disorders: Diabetic ketoacidosis

Musculoskeletal and Connective Tissue Disorders: Rhabdomyolysis

Nervous System: Cerebrovascular accident

Renal and Urinary Disorders: Urethral hemorrhage

Reproductive System and Breast Disorders (female): Vaginal hemorrhage

Respiratory, Thoracic, and Mediastinal Disorders: Pulmonary embolism, respiratory failure

Vascular disorder: Deep vein thrombosis

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of SAMSCA. Because these reactions are reported voluntarily from a population of an unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Neurologic: Osmotic demyelination syndrome

Investigations: Hypernatremia

Removal of excess free body water increases serum osmolality and serum sodium concentrations. All patients treated with tolvaptan, especially those whose serum sodium levels become normal, should continue to be monitored to ensure serum sodium remains within normal limits. If hypernatremia is observed, management may include dose decreases or interruption of tolvaptan treatment, combined with modification of free-water intake or infusion. During clinical trials of hyponatremic patients, hypernatremia was reported as an adverse event in 0.7% of patients receiving tolvaptan vs. 0.6% of patients receiving placebo; analysis of laboratory values demonstrated an incidence of hypernatremia of 1.7% in patients receiving tolvaptan vs. 0.8% in patients receiving placebo.

Immune System Disorders

Hypersensitivity reactions including anaphylactic shock and rash generalized [see CONTRAINDICATIONS].

Read the entire FDA prescribing information for Samsca (Tolvaptan Tablets )

Samsca - User Reviews

Samsca User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Samsca sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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