Tolvaptan (Jynarque/Samsca): Uses, Warnings, Doses, and Side Effects

Jynarque and Samsca are brand-name prescription medications. Both contain the same active ingredient, tolvaptan. However, these products treat different conditions and should not be used interchangeably. 

Jynarque

Jynarque is used to slow kidney function decline in adults who are at risk of rapidly progressing autosomal dominant polycystic kidney disease (ADPKD). 

ADPKD is an inherited kidney disease in which fluid-filled sacs (cysts) form in the kidneys. These cysts gradually impair kidney function as they grow and may lead to kidney failure. There’s no cure for this condition. 

Samsca 

Samsca is used to treat clinically significant low blood sodium levels (hyponatremia) in certain adults, including some people with heart failure or Syndrome of Inappropriate Antidiuretic Hormone (SIADH). 

Jynarque vs. Samsca

^*REMS (Risk Evaluation and Mitigation Strategies) is a drug safety program. The FDA requires REMS for certain medicines that have serious risks. 

Important Tolvaptan (Jynarque/Samsca) Information and Warnings

Jynarque

This medication can cause serious liver problems, which can be fatal or require you to have a liver transplant. That’s why it is available only through the Tolvaptan for ADPKD Shared System REMS. 

Stop taking this medication and call your healthcare provider immediately if you have:

• Unusual tiredness
• Loss of appetite
• Nausea
• Pain in the right upper stomach 
• Vomiting
• Fever
• Rash
• Itching
• Yellowing of the skin and eyes (jaundice)
• Dark urine
• Pale feces

Your healthcare provider will order blood tests to check your liver before you start Jynarque, 2 weeks and 4 weeks after starting treatment, monthly for the first 18 months, and every 3 months thereafter. 

Samsca

This medication may cause blood sodium levels to rise too quickly, potentially leading to osmotic demyelination syndrome (ODS). ODS is a serious neurological condition that can occur when severely low sodium levels are corrected too rapidly. It can cause serious neurological problems, coma, or death. 

Call your healthcare provider immediately if you have:

• Difficulty speaking or swallowing
• Drowsiness
• Confusion
• Mood changes
• Weakness or difficulty controlling movements in the arms or legs 
• Seizures

The following factors may increase the risk of ODS. Inform your healthcare provider if you have any of them. 

• Liver disease
• Malnutrition 
• Extremely low blood levels of sodium
• Chronic alcoholism

To lower the risk of ODS, your healthcare provider will start and restart treatment with Samsca in a hospital, where you can be monitored closely. You should drink water when you are thirsty. Also, you should keep water readily available at all times during treatment. 

Samsca may cause potentially fatal liver problems. Call your healthcare provider immediately if you have: 

• Unusual tiredness
• Loss of appetite
• Nausea
• Pain in the right upper stomach 
• Vomiting
• Fever
• Rash
• Itching
• Yellowing of the skin and eyes (jaundice)
• Dark urine
• Pale feces

Samsca should not be taken for more than 30 days because of the risk of liver injury. It should generally be avoided in people with underlying liver disease, including cirrhosis. 

Before Taking Tolvaptan (Jynarque/Samsca)

Jynarque

Before you receive your first dose of Jynarque, inform your provider if you:

• Are allergic to this product or any product component
• Have a history of extremely low sodium levels
• Are pregnant or plan to get pregnant
• Are breastfeeding or plan to breastfeed (Avoid breastfeeding during treatment)

Taking Jynarque with certain medicines may raise blood levels of tolvaptan. Ask your healthcare provider which medicines you can take with Jynarque. Your dose of Jynarque may need to be reduced. Talk to your healthcare provider before starting a new medication. 

Don’t take Jynarque if you:

• Have a history, signs, or symptoms of significant liver impairment or injury, other than uncomplicated polycystic liver disease
• Take certain medications that are strong CYP3A inhibitors
• Have an abnormal blood sodium level that has not been corrected
• Are unable to sense or appropriately respond to thirst
• Are dehydrated
• Have hypovolemia (abnormally low fluid volume in the body)
• Have a urinary tract obstruction that has not been corrected
• Are unable to produce urine

Samsca

Before you receive your first dose of Samsca, inform your provider if you:

• Are allergic to this product or any product component
• Have kidney or liver problems
• Cannot make urine
• Are unable to feel that you are thirsty
• Are pregnant or plan to get pregnant
• Are breastfeeding or plan to breastfeed
• Take desmopressin (dDAVP) 

Don’t take Samsca if you:

• Are allergic to tolvaptan or any of the ingredients in Samsca
• Need an urgent increase in your blood sodium level
• Are unable to sense or appropriately respond to thirst
• Have hypovolemic hyponatremia (low blood sodium associated with low fluid volume)
• Take certain medications called strong CYP3A inhibitors
• Are unable to produce urine

Tolvaptan (Jynarque/Samsca) Mechanism of Action 

Tolvaptan belongs to a class of medications called vasopressin V2 receptor antagonists. It works by blocking the effects of vasopressin, a hormone that normally causes the kidneys to retain water.

In people with ADPKD, blocking vasopressin V2 receptors helps reduce processes involved in kidney cyst growth and slows the decline in kidney function.

Tolvaptan also causes the kidneys to remove more water through urine without proportionally increasing sodium loss. In people with certain types of hyponatremia, this loss of excess water can help increase the concentration of sodium in the blood.

Tolvaptan (Jynarque/Samsca) Dosing

Jynarque

The starting total dose is 60 mg orally per day, which is divided into: 45 mg upon waking and 15 mg 8 hours later. If tolerated, the dose may be increased to 90 mg orally per day (60 mg upon waking and 30 mg 8 hours later).

The highest dose is 120 mg orally per day (90 mg upon waking and 30 mg 8 hours later). 

Samsca

The usual starting dose is 15 mg orally with or without food. The dose may be increased to 30 mg orally once daily after at least 24 hours. The maximum dose is 60 mg orally once daily. Don’t take this medication for longer than 30 days in order to reduce the risk of liver injury. 

Tolvaptan (Jynarque/Samsca) Proper Use and Storage

• Take your doses exactly as directed. Take your medicine around the same time each day.
• You may take this medication with or without food.
• Avoid drinking grapefruit juice while on treatment with this medication. 
• Drink enough water to prevent dehydration. 
• Call your healthcare provider if you have vomiting or diarrhea. 
• If you miss a dose, don’t double the dose. Continue your schedule as usual. 
• If you think you have overdosed, call your healthcare provider immediately. 
• If you need to stop taking Samsca because your healthcare provider told you to, ask them how much fluid you can take safely. 
• Keep all medications out of reach of children and pets. 
• Store Jynarque at77°F (25°C).
• Store Samsca between 68°F and 77°F (20°C and 25°C).

Tolvaptan (Jynarque/Samsca) Side Effects

Common Side Effects of Jynarque

• Thirst 
• Drinking more fluid than normal
• Frequent urination
• Increased urine output
• Urinating at night

Severe Side Effects of Jynarque

• Hypernatremia (elevated blood sodium levels)
• Dehydration and hypovolemia (loss of too much fluid from the body)

Jynarque increases water loss through urination and can cause dehydration and hypovolemia (abnormally low fluid volume). Drink enough water throughout the day and night to avoid becoming thirsty or dehydrated. If you cannot drink enough water for any reason, stop taking Jynarque and contact your healthcare provider. 

Call your healthcare provider if you experience any of the following:

• Dizziness
• Fainting
• Weight loss
• Changes in heart rhythm 
• Confusion
• Extreme weakness

Common Side Effects of Samsca

• Thirst
• Dry mouth
• Weakness
• Constipation
• Frequent urination
• Increased urine output
• Elevated blood glucose levels

Severe Side Effects of Samsca

Call your healthcare provider immediately if you have signs of dehydration, such as dizziness or feeling like you are going to pass out. Tell your healthcare provider if you have vomiting or diarrhea and difficulty drinking fluids.

Tolvaptan (Jynarque/Samsca) Cost

Cost can vary depending on your insurance plan, location, and pharmacy. Ask your insurance provider if your plan covers this medication or if you need prior authorization. 

Otsuka offers copay assistance for eligible patients who have been prescribed Jynarque. Contact us if you are interested in getting copay assistance for tolvaptan.