Tolvaptan (Samsca) is used to treat hyponatremia (low levels of sodium in the blood) in people who have heart failure (condition in which the heart cannot pump enough blood to all parts of the body), syndrome of inappropriate antidiuretic hormone (SIADH; condition in which the body produces too much of a certain natural substance that causes the body to retain water) or other conditions. Tolvaptan is in a class of medications called vasopressin V2 receptor antagonists. It works by increasing the amount of water released from the body as urine. Removing fluid from the body helps to increase the level of sodium in the blood.

Side Effects Of Tolvaptan

Tolvaptan (Samsca) may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • thirst
  • dry mouth
  • frequent, excessive urination
  • constipation

Some side effects can be serious. If you experience any of these symptoms or those listed in the WARNINGS and PRECAUTIONS section, call your doctor immediately:

  • loss of appetite
  • nausea
  • vomiting
  • fever
  • feeling unwell
  • unusual tiredness or weakness
  • itching
  • yellowing of the skin or eyes
  • dark urine
  • pain in the upper right part of the stomach
  • diarrhea
  • inability to drink normally
  • dizziness
  • faintness
  • vomit that is bloody or looks like coffee grounds
  • bloody or black and tarry stools
  • swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • hoarseness
  • hives
  • rash

Tolvaptan (Samsca) may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

Warnings & Precautions

Before taking tolvaptan (Samsca):

  • tell your doctor and pharmacist if you are allergic to tolvaptan (Samsca, Jynarque) , any other medications, or any of the ingredients in tolvaptan tablets. Ask your pharmacist or check the Medication Guide for a list of the ingredients.
  • tell your doctor if you are taking certain antifungals such as ketoconazole (Nizoral) or itraconazole (Sporanox); clarithromycin (Biaxin); certain medications for HIV such as indinavir (Crixivan), nelfinavir (Viracept), ritonavir (Norvir), or saquinavir (Invirase); desmopressin (dDAVP, Stimate); nefazodone; or telithromycin (Ketek). Your doctor may tell you not to take tolvaptan (Samsca) if you are taking one or more of these medications.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: angiotensin-converting enzyme (ACE) inhibitors such as benazepril (Lotensin, in Lotrel), captopril, enalapril (Vasotec, in Vaseretic), fosinopril, lisinopril (Prinivil, Zestril, in Zestoretic), moexipril, perindopril, (quinapril (Accupril, in Accuretic, in Quinaretic), ramipril (Altace), and trandolapril (Tarka); angiotensin II receptor blockers such as candesartan (Atacand), eprosartan, irbesartan (Avapro, in Avalide), losartan (Cozaar, in Hyzaar), olmesartan (Benicar, in Benicar HCT, in Tribenzor), telmisartan (Micardis, in Twynsta), and valsartan (Diovan, Prexxartan, in Entresto, in Exforge); aprepitant (Emend); barbiturates such as phenobarbital; carbamazepine (Carbatrol, Equetro, Tegretol); cyclosporine (Gengraf, Neoral, Sandimmune); desmopressin (dDAVP, Minirin, Noctiva), digoxin (Lanoxin); diltiazem (Cardizem, Diltzac, Tiazac); diuretics (water pills); erythromycin (E.E.S., ERYC, Erythrocin, PCE); fluconazole (Diflucan); phenytoin (Dilantin); potassium supplements; rifabutin (Mycobutin); rifampin (Rimactane, Rifadin, in Rifater, in Rifamate); rifapentine (Priftin); and verapamil (Calan, Verelan, in Tarka). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with tolvaptan (Samsca), so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
  • tell your doctor what herbal products you are taking or plan to take especially St John’s wort.
  • tell your doctor if you have kidney disease and do not produce urine, if you have severe vomiting or diarrhea, or if you have lost a lot of fluid from your body and feel dizzy or faint. Your doctor will probably tell you not to take tolvaptan (Samsca). Your doctor will also probably not prescribe tolvaptan (Samsca) if your sodium level must be increased very quickly.
  • tell your doctor if you have or have ever had a high level of potassium in your blood.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking tolvaptan (Samsca), call your doctor.

Dosage Of Tolvaptan

Tolvaptan (Samsca) comes as a tablet to take by mouth. It is usually taken once a day with or without food for no longer than 30 days. At the beginning of your treatment, you will be given tolvaptan (Samsca) at a regularly scheduled time in the hospital. If you are told to take tolvaptan (Samsca) at home after you are discharged, you should take it at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take tolvaptan (Samsca) exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of tolvaptan (Samsca) and gradually increase your dose, not more often than once every 24 hours.

Talk to your doctor about what you should do after you stop taking tolvaptan (Samsca). You will probably need to limit the amount of fluid you drink, and your doctor will monitor you carefully during this time.


Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your body’s response to tolvaptan (Samsca).

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.