Fingolimod capsules may lead to serious side effects, including the following:

1. Slow Heart Rate (Bradycardia or Bradyarrhythmia)

Fingolimod can cause your heart rate to slow down, particularly after the first dose. Before starting treatment, you will undergo an electrocardiogram (ECG) to monitor your heart's electrical activity.

All adults and children must be monitored by a healthcare professional for at least 6 hours after their first dose. Children switching from a 0.25 mg dose to 0.5 mg should also be observed for a minimum of 6 hours.

During this observation period:

• Your pulse and blood pressure will be checked hourly.

• A healthcare provider will watch for any serious side effects.

If your heart rate drops too low, you may experience symptoms such as:

• Dizziness

• Fatigue

• A sensation of your heart beating slowly or skipping beats

• Chest pain

These symptoms typically occur within the first 6 hours but can appear up to 24 hours after the initial dose. Another ECG will be conducted at the 6-hour mark to check for any heart abnormalities. If your heart rate remains low or shows irregularities, continued monitoring will be required.

If serious side effects occur—especially those requiring additional medication—you may need to stay overnight for further observation. The same 6-hour monitoring applies to your second dose the following day if complications occurred after the first.

People with specific heart conditions or those taking heart-affecting medications will also be observed overnight after their first dose.

In most cases, your heart rate returns to normal within one month of starting treatment. If you experience any symptoms of a slow heart rate, contact your doctor or seek emergency care immediately.

If you miss one or more doses of fingolimod capsules, you may need to be monitored again upon resuming treatment. Contact your doctor for guidance if you miss a dose. See the section titled “How should I take fingolimod capsules?” for more details.

2. Pregnancy

Do not become pregnant while taking fingolimod capsules or for at least two months after stopping treatment. The medication can harm an unborn baby. Always consult your doctor before planning a pregnancy.

3. Infections

Fingolimod may increase your risk of serious or life-threatening infections. Do not receive live vaccines during treatment or for two months after stopping the medication. If you receive a live vaccine during this time, you could contract the disease the vaccine is meant to prevent. Additionally, vaccines may be less effective while you are on this medication.

Speak with your doctor before receiving any vaccines during or shortly after treatment.

Human Papilloma Virus (HPV)

Due to increased infection risk, talk to your doctor about routine Pap smear screenings to monitor for HPV.

Fingolimod capsules lowers the number of white blood cells (lymphocytes) in your blood. This will usually go back to normal within 2 months of stopping treatment. Your doctor may do a blood test to check your white blood cells before you start taking fingolimod capsules. Call your doctor right away if you have any of these symptoms of an infection during treatment with fingolimod capsules, and for 2 months after your last dose of fingolimod capsules:

• fever
• tiredness
• body aches
• chills
• nausea
• vomiting
• headache with fever, neck stiffness, sensitivity to light, nausea, or confusion (these may be symptoms of meningitis, an infection of the lining around your brain and spine)

4. Progressive multifocal leukoencephalopathy (PML)

PML is a rare brain infection that usually leads to death or severe disability. If PML happens, it usually happens in people with weakened immune systems but has happened in people who do not have weakened immune systems. Symptoms of PML get worse over days to weeks. Call your doctor right away if you have any new or worsening symptoms of PML, that have lasted several days, including: 

• weakness on 1 side of your body
• loss of coordination in your arms and legs
• decreased strength
• problems with balance
• changes in your vision
• changes in your thinking or memory
• confusion
• changes in your personality

5. Vision Problems: Macular Edema

Fingolimod capsules may cause a vision condition called macular edema, which can mimic symptoms of a multiple sclerosis (MS) relapse, such as optic neuritis. In some cases, macular edema may develop without noticeable symptoms.

This condition most often occurs within the first 3 to 4 months after starting fingolimod, but it can develop at any time during treatment.

To help detect macular edema early:

• Your doctor should examine your eyes before starting treatment,

• Again at 3 to 4 months after starting,

• And periodically while you are on fingolimod.

• You should also have your eyes checked any time you experience changes in your vision.

Your risk is higher if you have diabetes or a history of eye inflammation (uveitis).

 Call your doctor right away if you have any of the following symptoms:

• blurriness or shadows in the center of your vision
• a blind spot in the center of your vision
• sensitivity to light

Find more indepth information about this drug here.