Medication Information Leaflet

What is this medication for?

This medication is used to treat hyponatremia, where the sodium level in the blood is below normal. Hyponatremia may occur in patients with heart failure or ‘Syndrome of Inappropriate Antidiuretic Hormone Secretion’ (SIADH), which is a condition where the body retains too much water. Excessively low sodium levels may result in difficulties in concentration and memory, or in maintaining your balance. In serious cases, brain swelling and seizures might occur.

Tolvaptan may also be used with other medications, such as a diuretic (a medication which helps to remove excess water and salt from the body), to reduce the amount of water in your body.

Tolvaptan works by blocking vasopressin, a hormone that reduces water loss from the body. With increased urine production, excess water is removed and sodium levels in the blood will increase.

How should I take/use this medication?

• Do not stop taking your medication without checking with your healthcare professional
• Take Tolvaptan in the morning to avoid night time urination
• You may take this medication with or without food
• Tablets must be swallowed whole without chewing, with a glass of water
• Tolvaptan will be initiated in a hospital where your sodium levels can be monitored. If you have been told to continue taking Tolvaptan after you leave the hospital, it is important that you do not stop or restart the medication on your own

What should I do if I forget to take/use this medication?

If you forget to take a dose, take it as soon as you remember. Then take your next dose at the usual time. Do not take two doses to make up for the missed dose

What precautions should I take?

• As Tolvaptan exists under two different brand names and different strengths (Samsca^®, Jinarc^®) for different treatment purposes, you should not switch between the two brands unless otherwise instructed by your doctor.

Inform your healthcare professional if:

• You are allergic to this medication or any of the other ingredients of this medication
• You are pregnant, planning to become pregnant, or breastfeeding
• You are taking any other medications, including supplements, traditional medications and herbal remedies
• You have uncontrolled diabetes, liver or kidney problems
• You have difficulty in realising when you are thirsty or unable to drink sufficient amounts of water
• You have difficulty in passing urine

What are some common side-effects of this medication?

• Dry mouth and thirst
  • Ensure that you are able to drink sufficient amounts when you are thirsty
• Constipation
  • Drink plenty of water and include enough fruits and vegetables in your diet
• Dizziness, weakness
  • Getting up or changing posture slowly may help. Take a rest by sitting or lying down if you feel dizzy
• Frequent, excessive urination
  • Take your dose in the morning to minimize bathroom trips during the night
  • Make sure to go to the bathroom before meetings, movies, or other social events

What are some rare but serious side-effects that I need to seek medical advice immediately?

Very rarely, Tolvaptan may cause injury to the liver. Symptoms of liver problems include: Dark brown urine, light coloured stools (pale grey/ clay coloured), nausea, vomiting, loss of appetite, yellowing of skin or eyes

Tolvaptan may also cause severe dehydration, if left untreated. Symptoms of dehydration include: Dark yellow and strong-smelling urine, reduced urination, unusual tiredness, feeling dizzy or light-headed or dry mouth, lips, eyes or skin

Lastly, the symptoms of a drug allergy include one or more of the following:

• Swollen face/eyes/lips/tongue
• Difficulty in breathing
• Itchy skin rashes over your whole body

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately

What food or medication should I avoid when I take this medication?

Avoid taking grapefruit and grapefruit juice when you are taking this medication as these may interact with your medication and increase the risk of side-effects.

Some medications may interact with Tolvaptan and affect their effectiveness or increase the risk of side-effects. However, these medications may also be important for your treatment. Inform your healthcare professional of any medications you are currently taking. Examples include:

• Medications for bacterial infections (eg clarithromycin, erythromycin)
• Medications for fungal infections (eg ketoconazole, itraconazole)
• Medications for viral infection (eg ritonavir)
• Medications for heart conditions (eg diltiazem, verapamil, digoxin)
• Medications for treating Tuberculosis (eg Rifampicin)
• Medications for managing Epilepsy (eg Phenytoin, Carbamazepine)

Consult your healthcare professional if you are unsure whether your existing medications can be taken together with this medication.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing into the rubbish chute or bin.

Disclaimers

Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on May 2023