Tolvaptan belongs to the class of medications called vasopressin receptor antagonists. It is used to treat autosomal dominant kidney disease (ADPKD), a genetic disorder which results in cysts (fluid filled sacs) on the kidneys. These cysts can cause damage to the kidneys and potentially lead to kidney failure.

Tolvaptan works by blocking the effect of a hormone in the body called vasopressin, which promotes cyst growth. Tolvaptan helps to reduce the growth of the cysts and to protect the kidneys from damage.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

Tolvaptan is usually taken twice a day in two different doses. The recommended starting dose of tolvaptan is a total daily dose of 60 mg taken as a split dose of 45 mg + 15 mg. The dose may be increased after seven days to a total of 90 mg daily, taken as a split dose of 60 mg + 30 mg.  The maximum daily dose is 120 mg, taken as a split dose of 90 mg + 30 mg. Your doctor may lower the dose depending on other medications you are taking.

The higher dose tablet in the combination pack should be taken in the morning, and the lower dose tablet should be taken approximately 8 hours later.

Tolvaptan may be taken with food or on an empty stomach. If you become thirsty, you may drink fluids. Avoid grapefruit or grapefruit juice while you are taking tolvaptan.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor.

If you miss a dose, skip the missed dose and continue with your regular prescribe dose and dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

15 mg + 15 mg

15 mg
Each non-scored, bevelled-edged, shallow-convex, blue, triangular tablet debossed with "otsuka" and "15" on one side, contains 15 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

30 mg + 15 mg

30 mg
Each non-scored, bevelled-edged, shallow-convex, blue, round tablet debossed with "otsuka" and "30" on one side contains 30 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

15 mg
Each non-scored, bevelled-edged, shallow-convex, blue, triangular tablet debossed with "otsuka" and "15" on one side, contains 15 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

45mg + 15 mg

45 mg
Each non-scored, blue, square, shallow-convex tablet debossed with "otsuka" and "45" on one side, contains 45 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

15 mg
Each non-scored, bevelled-edged, shallow-convex, blue, triangular tablet debossed with "otsuka" and "15" on one side, contains 15 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

60mg + 30 mg

60 mg
Each non-scored, bevelled-edge, blue, modified rectangular, shallow- convex, beveled-edge tablet, debossed with "otsuka" and "60" on one side, contains 60 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

30 mg
Each non-scored, bevelled-edged, shallow-convex, blue, round tablet debossed with "otsuka" and "30" on one side contains 30 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

90mg + 30 mg

90 mg
Each non-scored, blue, pentagonal, shallow-convex tablet debossed with "otsuka" and "90" on one side, contains 90 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

30 mg
Each non-scored, bevelled-edged, shallow-convex, blue, round tablet debossed with "otsuka" and "30" on one side, contains 30 mg of tolvaptan. Nonmedicinal ingredients: corn starch, hydroxypropyl cellulose, lactose monohydrate, low-substituted hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and FD&C Blue No. 2 Aluminum Lake as colourant.

Do not take tolvaptan if you:

• are allergic to tolvaptan or any ingredients of the medication
• are allergic to benzazepine or benzazepine derivatives (e.g., mirtazapine)
• have been asked by your doctor to permanently stop taking this medication in the past
• are not producing urine
• have high blood sodium
• have excessive loss of body water
• cannot sense or respond to thirst
• have impaired liver function
• have galactose intolerance, Lapp lactase deficiency, or glucose-galactose  malabsorption
• are using certain other medications, such as itraconazole, ketoconazole, clarithromycin, HIV protease inhibitors, nefazodone
• are pregnant or breastfeeding

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• decreased appetite
• diarrhea
• dizziness
• dry mouth
• fatigue
• headache
• increased urine volume
• indigestion
• itchy skin
• loss of appetite
• more frequent urination
• muscle spasms
• rash
• stomach pain
• thirst
• trouble sleeping
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• signs of dehydration (e.g., dry or sticky mouth, decreased urine production, decreased tear production, dizziness, thirst, nausea, vomiting)
• signs of gout (e.g., joint pain, usually in the big toe, followed by redness, swelling, warmth)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• signs of high levels of potassium in the blood (e.g., irregular heartbeats, muscle weakness, general feeling of being unwell)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of angioedema (e.g., swelling of the face, mouth, hands, or feet)
• signs of a serious allergic reaction (e.g., swelling of face or throat, hives, or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Blood pressure: Tolvaptan may cause a decrease in blood pressure in people who are taking medication to lower blood pressure. You should move slowly when you are rising from a reclining to an upright position to reduce the risk of dizziness.  If you are being treated for high blood pressure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Dehydration: Tolvaptan causes an increase in the amount of urine produced as it causes the body to eliminate fluid. As a result, it is possible for dehydration to occur. Drink fluids when you feel thirsty and be aware of other signs of dehydration such as muscle cramps, nausea and vomiting, rapid pounding heartbeat, as well as a feeling of dry stickiness in the mouth.

Dizziness: Tolvaptan may cause dizziness, affecting your ability to drive or operate machinery. Avoid these and other hazardous tasks until you have determined how this medication affects you.

Fluid and electrolyte balance: Tolvaptan may cause the levels of electrolytes such as potassium and sodium in the blood to change while taking this medication. If you experience symptoms of fluid and electrolyte imbalance such as muscle pains or cramps; dry mouth; numb hands, feet, or lips; or racing heartbeat, contact your doctor as soon as possible. Your doctor will do blood tests regularly to monitor the levels of these electrolytes in your blood while you are taking this medication.

Gout: Tolvaptan may cause an increase in uric acid in the blood, causing gout. Symptoms of an acute gout attack include sudden pain, swelling, and stiffness in the affected joint, often the big toe. You may also experience a fever. If this is your first attack, seek medical attention as soon as possible. If you have had gout attacks before, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Grapefruit juice: Grapefruit juice affects how tolvaptan is removed from the body and may cause too much of the medication to build up in the body and cause possibly harmful side effects. Do not drink grapefruit juice or eat grapefruit at any time while taking this medication for treatment.

Liver function: Decreased liver function or liver disease can cause tolvaptan to build up in the body, causing side effects. Tolvaptan may reduce liver function and can cause liver failure. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if tolvaptan passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.