Tolvaptan (Oral)

Tolvaptan is used to treat hyponatraemia in patients with heart failure or syndrome of inappropriate antidiuretic hormone secretion (SIADH).


Tolvaptan works in the kidneys to help the body maintain the correct levels of sodium in the blood. It is used to treat hyponatraemia in patients with heart failure or syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Hyponatraemia is a condition that occurs when the level of sodium in your blood is abnormally low. Sodium is an electrolyte that helps with the regulation of the amount of water that is in your cells.

Hyponatraemia can be caused by a range of factors, from underlying medical conditions to drinking too much water during endurance sports. Depending on the cause of hyponatraemia, it can be solved by cutting back on the amount of water consumed. Tolvaptan would only be used in cases where the problem is caused by underlying health issues, including heart failure and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the inappropriate and continued secretion or action of the antidiuretic hormone arginine vasopressin (AVP). This results in impaired water secretion and leads to an imbalance in sodium levels.

Samsca, which contains the active substance Tolvaptan, belongs to a group of medicines call vasopressin antagonists. Vasopressin is a hormone that helps prevent the loss of water from the body by reducing urine output. Antagonist means that it prevents the vasopressin having its effect on water retention, leading to a reduction in the amount of water in the body. This occurs by increasing the urine production and as a result, it increases the concentration of sodium in the blood, bringing patients back to normal levels.

Tolvaptan is only available with a doctor's prescription and it should only be taken as directed by your doctor. The first dose should be taken with a doctor on hand to monitor the effects. Do not exceed the dose or period of time taken as instructed by your doctor.

This medicine should first be taken in a hospital. Your doctor will check your response to the medicine and monitor you for any unwanted reactions that may occur.

Tolvaptan should come with a medication guide and you should follow the instructions closely.

Tolvaptan can damage the liver and should not be taken for more than 30 days.

Conditions treated

  • Hyponatraemia

Type of medicine

  • Hormone

Side Effects

Medicines can cause unwanted side effects and with Tolvaptan it is important to seek medical attention if they occur. Side effects can be a sign of liver problems or osmotic demyelination syndrome (ODS) which both need immediate attention. For the first few days, the patient will be monitored after taking the medicine.

If you experience any of the following common or less common side effects, you should inform your doctor:

More common

  • Abdominal or stomach pain
  • Blurred vision
  • Dry mouth
  • Flushed, dry skin
  • Frequent urination
  • Fruit-like breath odor
  • Increased hunger
  • Increased thirst
  • Increased urination
  • Increased volume of pale, dilute urine
  • Nausea
  • Sweating
  • Thirst
  • Difficulty breathing
  • Unexplained weight loss
  • Unusual tiredness or weakness
  • Vomiting

Less common

  • Abdominal or stomach tenderness
  • Anxiety
  • Blood in the urine
  • Bloody stools
  • Blue lips, fingernails, or skin
  • Bruising
  • Chest pain
  • Confusion
  • Cough
  • Coughing or vomiting blood
  • Dark-colored urine
  • Dizziness or lightheadedness
  • Fainting
  • Fast, slow, irregular or shallow heartbeat
  • Fever
  • Irregular, fast or slow, or shallow breathing
  • Loss of consciousness
  • Muscle cramps or spasms
  • Muscle pain or stiffness
  • Pain, redness, or swelling in the arm or leg
  • Persistent bleeding or oozing from puncture sites, mouth, or nose
  • Pink or red urine
  • Rash
  • Rectal bleeding
  • Shortness of breath
  • Sudden shortness of breath or troubled breathing
  • Sweating
  • Vaginal bleeding

Some side effects may also occur that do not need medical attention. The following side effects are not a cause for concern, but you should inform your medical professional if the side effects are persistent and bothersome:

Very common

  • Thirst
  • Nausea

More common

  • Difficulty having a bowel movement (stool)
  • Lack or loss of strength

Less common

  • Loss of appetite
  • Weight loss

Other side effects may occur. If you notice any other side effects, contact your health professional for advice on whether there is any concern.


Dosing will be different for different patients. Follow instructions given by your doctor and read the directions on the label. The following information is based on averages only. Do not change the dose you have been instructed to take by your doctor.

The dose taken will depend on the strength of the medicine that you are given and the number of days you take it for, the number of times per day that you take it and the time between doses will depend on the medical problem that you are taking the medication for.

To take the medicine, swallow the tablet with a glass of water. Take the tablets in the morning where possible. They should not be chewed and can be taken with or without food.

Typical doses:

  • Adults - Adults will be given 15 milligrams once a day at first. This will be adjusted by the doctor to your needs. This dose does not usually exceed more than 60 milligrams per day.
  • Children - Use and dose will be determined by the doctor.

If a dose is missed, you should take it as soon as possible. If you are close to your next dose, however, you should skip the dose and return to your regular schedule. Do not take double doses of this medicine.


Medicines can interact with one another in the body. Some medicines can stop others from working and some medicines can react aggressively with one another, causing violent reactions and serious problems. You should always inform your doctor of any other drugs or medicines that you are taking before being prescribed Tolvaptan.

Using Tolvaptan with any of the following medicines is not recommended, although your healthcare professional may still decide to treat you with both or change the other medicine you are taking:

  • Boceprevir
  • Clarithromycin
  • Cobicistat
  • Conivaptan
  • Delavirdine
  • Idelalisib
  • Indinavir
  • Itraconazole
  • Ketoconazole
  • Nefazodone
  • Nelfinavir
  • Posaconazole
  • Ritonavir
  • Saquinavir
  • Telaprevir
  • Telithromycin
  • Tipranavir
  • Voriconazole

Taking Tolvaptan with any of the following is not usually recommended but, in some cases, your doctor may prescribe both:

  • Amobarbital
  • Amprenavir
  • Aprepitant
  • Atazanavir
  • Butabarbital
  • Carbamazepine
  • Ceritinib
  • Crizotinib
  • Digoxin
  • Diltiazem
  • Dronedarone
  • Efavirenz
  • Eliglustat
  • Erythromycin
  • Fluconazole
  • Fosamprenavir
  • Fosaprepitant
  • Fosphenytoin
  • Imatinib
  • Lumacaftor
  • Modafinil
  • Nevirapine
  • Oxcarbazepine
  • Pentobarbital
  • Phenobarbital
  • Phenytoin
  • Pioglitazone
  • Rifabutin
  • Rifampin
  • Rifapentine
  • Secobarbital
  • Simeprevir
  • St John's Wort
  • Verapamil
  • Vincristine
  • Vincristine Sulfate Liposome

Tolvaptan should not be taken with the following medicines. These medicines can increase the risk of more serious side effects.

  • clarithromycin (Biaxin®)
  • indinavir (Crixivan®)
  • itraconazole (Sporanox®)
  • ketoconazole (Nizoral®)
  • nefazodone (Serzone®)
  • nelfinavir (Viracept®)
  • ritonavir (Norvir®)
  • saquinavir (Fortovase®, Invirase®)
  • telithromycin (Ketek®)

Tolvaptan should not be taken with grapefruit juice. Grapefruit juice can intensify the effects of the medicine and cause serious issues.


It is very important that you have regular contact with a doctor while taking this medicine. Regular visits will be needed so that your doctor can confirm that the medicine is working properly. This will allow them to check that it is working properly and blood samples can be taken to check for any unwanted side effects that may be occurring unseen.

Inform your medical professional right away if you experience any of the following side effects:

  • Drowsiness
  • Confusion
  • Mood changes
  • Muscle weakness in the arms
  • Muscle weakness in the legs
  • Seizures or convulsions
  • Trouble speaking
  • Trouble swallowing
  • Trouble controlling movements

These side effects can be signs of a serious and rare condition called osmotic demyelination syndrome (ODS). This can occur when the sodium level in the body rises too quickly.

Tolvaptan can also cause serious liver problems. You should contact your doctor immediately if you experience any of the following:

  • Pain in the upper stomach
  • Pale stools
  • Dark urine
  • Loss of appetite
  • Nausea
  • Vomiting
  • Yellow eyes
  • Yellow skin

It is important to stay hydrated when taking Tolvaptan. You should always have water on hand to drink if you think you are thirsty and you should tell your doctor right away if you think you are dehydrated. In some cases, your doctor may limit the amount of liquid you consume. In this case, you should follow the instructions and only consume the amount of liquid outlined by your doctor.

Consult your doctor before taking any medicines that contain potassium.

Do not drink grapefruit juice when taking Tolvaptan. Grapefruit juice intensifies the effect of the medicine in your body and may increase effects.

Do not take any other medicines unless instructed by your doctor. This includes over the counter medicines and vitamin supplements. Vitamin supplements and herbal remedies can react with Tolvaptan.

Other medical conditions can also affect the use of this medicine. Tell your doctor if you have any other problems. This is particularly important if you have any of the following conditions:

  • Chronic alcoholism
  • Cirrhosis
  • Severe liver disease
  • Malnutrition
  • Anuria
  • Hypovolemic hyponatraemia
  • Severe kidney disease
  • Are unable to sense or respond to thirst

This medicine should not be used to treat the following conditions:

Pregnant women should avoid Tolvaptan. Animal studies have shown toxicity levels that indicate significant interference with unborn fetuses.

Breastfeeding women should also avoid Tolvaptan. Animal studies have found the medicine present in milk.

All patients should be monitored no later than six hours after first treatment and every six hours for the first one or two days of treatment until the patient has stabilised. Treatment should be stopped immediately if there is a rapid increase in serum-sodium concentration.


Store this medicine in a closed container at room temperature. Keep away from heat, moisture, direct light and cold conditions. Prevent this medicine from freezing.

Keep out of reach of children at all times.

Do not keep once it has expired.

Dispose of this medicine as instructed by your medical professional.


Samsca, which contains the active substance Tolvaptan, is used to treat low sodium levels in adults as a result of heart failure or a disease called syndrome of inappropriate antidiuretic hormone secretion (SIADH) where the kidneys retain too much water. The condition treated is hyponatraemia, which is a deficiency of sodium in the bloodstream.

Tolvaptan can interact with a wide range of drugs and is not suitable for use as treatment with a wide range of conditions. Ensure you tell your doctor about all substances that you are taking and about any underlying medical conditions that you may have before you start taking this medicine.

Tolvaptan must be administered under close medical monitoring when first administered and medical overview will need to be given every 6 hours for 1-2 days until levels have stabilized.

Tolvaptan should not be taken for longer than 30 days at a time and should only be taken as instructed.

Tolvaptan reacts with grapefruit juice and this should not be consumed when taking the medicine.

Tolvaptan can result in liver problems so side effects should be reported immediately to your doctor.

Pregnant and breastfeeding women should not use Tolvaptan. Animal studies have shown high toxicity in fetuses and significant presence of the drug in milk.

Dosing will be different for different patients. Follow instructions given by your doctor and read the directions on the label. If a dose of Tolvaptan is missed it should be taken as soon as possible. A double dose of the drug should never be taken, however.

Tolvaptan is not suitable for the treatment of hyponatraemia in cases other than heart failure or (SIADH). Hyponatraemia caused by other factors should not be treated in the same manner.

Last Reviewed:
December 24, 2017
Last Updated:
April 05, 2018