SIDE EFFECTS: See also Warning section. Thirst, dry mouth, loss of appetite, constipation, or weakness may occur. If any of these effects last or get worse, 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 vomiting or diarrhea that doesn't stop, and you cannot drink normally. Contact your doctor right away 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 right away 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, such as: nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine. 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.

PRECAUTIONS: 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: diabetes, liver disease, inability to make urine (anuria), use/abuse of alcohol. To prevent loss of too much body water (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 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 breast-feeding.

DRUG INTERACTIONS: 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), boceprevir, cobicistat, HIV protease inhibitors (such as lopinavir, ritonavir), macrolide antibiotics (such as clarithromycin, erythromycin), ribociclib, rifamycins (such as rifabutin, rifampin), St. John's wort, drugs used to treat seizures (such as carbamazepine, phenytoin), telaprevir, among others.

OVERDOSE: 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 their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.