This medication is used by people who have a certain inherited kidney problem (autosomal dominant polycystic kidney disease-ADPKD). This inherited kidney problem leads to the growth of fluid-filled sacs (cysts) in your kidneys. Over time, the cysts grow in size, which can damage the way your kidneys work and lead to kidney failure. Tolvaptan belongs to a class of drugs known as vasopressin receptor antagonists. It works by slowing the growth of kidney cysts caused by ADPKD. This effect helps protect your kidneys from damage and failure.

Different brands of this medication have different uses. Do not change brands of this medication unless directed by your doctor.

Read the Medication Guide provided by your pharmacist before you start using tolvaptan and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually 2 times a day (once when you wake up and once 8 hours later). To prevent dehydration, always have water ready to drink while taking tolvaptan. Drink water when you are thirsty and throughout the day and night if awake. Stop taking this medication and tell your doctor right away if you have vomiting or diarrhea, or if you cannot drink enough water for any reason.

The dosage is based on your medical condition and response to treatment. To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Avoid eating grapefruit or drinking grapefruit juice while using this medication unless your doctor or pharmacist says you may do so safely. Grapefruit can increase the chance of side effects with this medicine. Ask your doctor or pharmacist for more details.

See also Warning section.

Increased urination and thirst are common side effects. Dry mouth, loss of appetite, or upset stomach may also occur. If any of these effects bother you or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor 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.

Dehydration can occur. The risk is increased if you have vomiting or diarrhea that doesn't stop, and you cannot drink normally. Tell your doctor right away if you notice any symptoms of dehydration, such as fast heartbeat or dizziness/lightheadedness.

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 or at www.fda.gov/medwatch.

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

Before taking tolvaptan, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• liver disease
• gout
• trouble urinating (such as due to enlarged prostate, blockage, inability to make urine)
• abnormal sodium (salt) levels in the blood

To prevent dehydration while taking this medication, you must be able to replace fluids by drinking. Before taking this medication, tell your doctor if you are not able to drink normally or if you cannot feel if you are thirsty. (See also How to Use section.)

This drug may make you dizzy, especially if you are also taking medication(s) for high blood pressure. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

This medication may rarely make your blood sugar rise, which can cause or worsen diabetes. If you have diabetes, check your blood sugar regularly as directed and share the results with your doctor. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

A product that may interact with this drug is:

• desmopressin

Other medications can affect the removal of tolvaptan from your body, which may affect how tolvaptan works. Examples include azole antifungals (such as ketoconazole, itraconazole), cobicistat, HIV protease inhibitors (such as lopinavir), macrolide antibiotics (such as clarithromycin, erythromycin), ribociclib, rifamycins (such as rifabutin, rifampin), ritonavir, St. John's wort, drugs used to treat seizures (such as carbamazepine, phenytoin), among others.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

If you miss a dose, skip the missed dose. Take your next dose at the regular scheduled time and at the dose prescribed for that time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.