Filspari (sparsentan) is used for certain kidney conditions, including immunoglobulin A nephropathy (IgAN) and focal segmental glomerulosclerosis (FSGS). Filspari may help protect the kidneys in some people with these conditions.
Like most medicines, Filspari may cause side effects. Some are more common than others, and some side effects may improve as your body adjusts to treatment.
Keep reading to learn about common side effects of Filspari, what you can do to prevent them, what to do if they happen, and when to tell your health care provider.
This article does not include all possible side effects of Filspari. Tell your health care provider if you have side effects that are ongoing or bother you, even if they are not listed here.
Common Filspari Side Effects
The most common side effects reported in clinical studies include:
- High potassium levels
- Low blood pressure
- Fluid retention
- Kidney problems
- Dizziness
- Low red blood cell levels (anemia)
Some of these side effects are temporary and often improve on their own, but some can become severe if left untreated. Contact your health care provider if you experience symptoms that feel severe or don’t go away. Do not stop taking Filspari unless your provider recommends it.
Serious Side Effects of Filspari
Serious Filspari side effects are less common and include:
- Liver damage
- Low blood pressure
- Kidney problems
- High potassium levels
- Fluid retention
- Allergic reactions
If you think you may be having a serious side effect, contact your health care provider right away. In some cases, severe symptoms may require urgent medical care. Your provider can look at your symptoms and explain what steps to take next.
The sections below explain common Filspari side effects and what you can do to help reduce or relieve them.
Tips for Managing Filspari Side Effects
Some side effects can be managed with simple strategies.
1. Fluid retention
Fluid retention or edema is a common side effect of Filspari. Possible symptoms may include swollen hands, legs, ankles, feet, or unusual weight gain.
Tell your health care provider if you notice edema. They may prescribe a treatment for it, such as a diuretic, also called a water pill. They may also recommend other things you can do at home to reduce fluid retention, such as the following:
- Keep your legs raised when sitting.
- Wear support or compression stockings.
- Limit the amount of salt you eat.
Contact your health care provider if your symptoms of fluid retention feel severe or do not improve. They may adjust your dose or treatment plan. Do not stop taking Filspari unless your provider recommends it.
2. Low blood pressure
Low blood pressure, including when you change positions (orthostatic hypotension), is a common side effect of Filspari. To help prevent this, your health care provider may adjust the dose of any blood pressure medicines you take when you start Filspari.
You can also take steps to reduce your risk. Be careful not to get up too quickly. If you feel dizzy, sit or lie down right away until the dizziness stops, then take your time getting up again. Staying hydrated may also help.
Mild low blood pressure may get better as your body gets used to the medicine. Tell your health care provider if your symptoms do not improve. They may lower your Filspari dosage or pause treatment.
Tell your health care provider right away if you have symptoms of low blood pressure or orthostatic hypotension, such as dizziness, feeling lightheaded, or fainting upon standing. If your symptoms feel severe or life-threatening, call 911 or go to the nearest emergency room right away.
3. Dizziness
Dizziness is a common side effect of Filspari. It can happen on its own or because of low blood pressure, as discussed above.
Dizziness symptoms can include a feeling of being lightheaded, unsteady, or faint.
Dizziness can happen for several reasons, including dehydration, inner ear problems, or as a side effect of certain medicines. Stay well hydrated so that dehydration does not make dizziness worse.
If you feel dizzy, you can try lying down and closing your eyes for a few minutes. Then, it may help to sit up very slowly, avoiding any sudden or quick movements. Then slowly stand up.
Tell your health care provider if dizziness worsens or does not go away. They may adjust your dosage or pause or stop the medicine.
4. High potassium levels
Hyperkalemia or high potassium levels is a common side effect of Filspari. You may be at a higher risk for this side effect if you have advanced kidney disease or take other medicines that can raise your potassium levels.
Possible symptoms of high potassium levels include muscle weakness, nausea or vomiting, trouble breathing, or an abnormal heart rhythm.
Your health care provider will likely monitor your potassium levels while you are taking Filspari. Be sure to keep all of your appointments, including those for lab tests.
To lower your risk of high potassium levels, be sure to tell your health care provider about all of the medicines you take, including vitamins or supplements, and limit the use of salt substitutes, as they often have lots of potassium in them.
If your potassium levels get too high, your health care provider may reduce your dose or suggest you stop taking Filspari. If your symptoms feel severe or life-threatening, call 911 or go to the nearest emergency room right away.
5. Kidney damage
Kidney damage can happen when taking Filspari. You may be at a higher risk for kidney damage if you have certain other health conditions or take certain medicines.
Possible symptoms of kidney damage include:
- Reduced need to pee
- Swelling in your feet, ankles, or legs
- Trouble catching your breath
- Chest pain or pressure
- Confusion
- Nausea
To reduce your risk of kidney damage from Filspari, be sure to tell your health care provider about all of your health conditions, especially if you have any of the following:
- Heart failure
- Other kidney problems, including renal artery stenosis or chronic kidney disease
- You have trouble drinking enough fluids to stay well hydrated
Tell your health care provider if you have any new or worsening symptoms of kidney damage. They may pause or stop the medicine. If your symptoms feel severe or life-threatening, call 911 or go to the nearest emergency room right away.
Frequently Asked Questions About Filspari Side Effects
Can Filspari cause birth defects?
Filspari may cause birth defects. If you can get pregnant, your health care provider will likely have you take a pregnancy test before you start taking it. You should use an effective birth control method before starting Filspari, during treatment, and for two weeks after stopping it. Talk to your health care provider about effective birth control options. If you become pregnant while taking Filspari, stop taking it and contact your health care provider right away.
Can I drive after taking Filspari?
It depends. Filspari can cause dizziness, which can affect your alertness or coordination. You should not drive or do other activities that require alertness or coordination until you know how Filspari affects you.
Reducing Your Risk of Filspari Side Effects
You can reduce your risk of side effects by:
- Taking Filspari exactly as prescribed
- Telling your health care provider about all of the medicines you take, including vitamins and supplements
- Telling your health care provider about all of your health conditions
- Keeping track of any new or changing symptoms and sharing them with your health care provider
- Telling your health care provider about side effects that do not improve or start to interfere with daily activities
Your health care provider can help you decide whether changes to your treatment plan are needed.