Tolvaptan is used to treat hyponatraemia (low sodium level in the blood) in individuals with heart failure (weakness and inability of the heart to pump blood) and syndrome of inappropriate antidiuretic hormone secretion (a condition in which there are excessive levels of antidiuretic hormones [hormones that help the kidneys conserve the right amount of water in the body]).
This medicine may also be used to treat autosomal dominant polycystic kidney disease (an inherited disorder characterised by the growth of small fluid-filled sacs called cysts in the kidneys) in individuals with rapidly progressing disease.
Take Tolvaptan exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
Ask your doctor or pharmacist whether you should take this medicine with or without food. Different brands of this medicine may be taken differently.
Tolvaptan must be taken regularly for it to be effective. Continue taking this medicine even when you feel better. Do not stop taking it unless instructed by the doctor.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, let your doctor and pharmacist know.
Do not take Tolvapatan if you ever had an allergic reaction (e.g. rashes, breathlessness, swollen eyes) to this medicine or other benzazepine derivatives such as benazepril (medicine for high blood pressure) or mirtazapine (medicine to treat depression).
Alert your doctor if you have the following conditions:
- unable to urinate
- cannot feel you are thirsty
- low volume of circulating fluids in the body
- high sodium level in the blood
- high level of liver enzymes in the blood
as Tolvaptan may not be suitable for you.
Do not take this medicine if you are pregnant. If you become pregnant while on Tolvaptan therapy, alert your doctor immediately. This medicine may cause harm to your unborn child.
Do not take this medicine if you are breastfeeding.
Do not take Tolvaptan with medicines used to treat fungal infections, certain antibiotics, and certain medicines for HIV infection. Please see the section "Can I take this with other medicines?" below for more information.
Inform your doctor if you have the following conditions:
- difficulty in passing urine
- prostate enlargement
- cancer
- liver disease
- kidney disease
- diabetes
Do not switch between different brands unless advised by your doctor.
Tolvaptan may cause water loss since it increases the production of urine. It is important that you have access to water and that you are able to drink adequate amounts when you feel thirsty.
Why is it important to keep my appointments with the doctor?
Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.
- Liver function tests must be done before treatment to know if this medicine is suited for you to take.
- Routine tests (e.g. liver function, electrolyte levels) may be done while you are being treated with this medicine. Your doctor will advise you about how often you need to have these tests.
Tolvaptan may cause dizziness or generalised weakness. If affected, do not drive or take part in any activity in which you need to be alert.
Other side effects include any of the following: constipation, dry mouth, nausea, diarrhoea, headache, and itching.
Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
- rashes, breathlessness, swelling of the face, eyes or mouth
- confusion, loss of balance or coordination, sudden changes in behaviour
- yellowing of the skin or eyes, abdominal pain, dark coloured urine, tiredness, swelling in the legs and ankles
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Do not take Tolvaptan if you are taking any of these medicines:
- certain antibiotics e.g. clarithromycin
- certain medicines to treat fungal infection e.g. ketoconazole, itraconazole
- certain medicines for HIV infection e.g. ritonavir
Inform your doctor and pharmacist if you are taking any of these medicines:
- medicines for epilepsy (fits or seizures) e.g. phenytoin, carbamazepine
- cholesterol-lowering medicines e.g. lovastatin, rosuvastatin
- rifampicin (medicine to treat TB [an infection known as tuberculosis])
- digoxin (medicine for heart disease)
- St. John's wort (herbal medicine)
This list does not include all medicines that may interact with Tolvaptan.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements, and medicines that you buy without a prescription.
Avoid alcohol.
Avoid excessive consumption of grapefruit or grapefruit juice (more than 1 litre a day).
Store in a cool, dry place away from the reach of children.
Medicines must not be used past the expiry date.
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