This information describes side effects that may happen after your intraocular (IN-truh-AH-kyoo-ler) methotrexate (MEH-thoh-TREK-sayt) injection. It also describes how taking folic acid supplements can help reduce these side effects.
About your intraocular methotrexate injection
An intraocular injection is a shot that puts medicine right into your eye. You’re getting an intraocular injection of a medicine called methotrexate to treat your eye disease. You may get the injection in 1 or both eyes, depending on which eye is affected.
Most people get a series of methotrexate injections over a few months. Your healthcare provider will tell you how many injections you’ll need and how often you’ll get them.
Your care team will give you the resource About Your Intraocular Injection. It explains what to expect before, during, and after your injection.
Side effects of your intraocular methotrexate injection
A methotrexate injection can sometimes affect the cornea (the clear, outer layer of your eye). It can cause side effects, such as:
- Blurry vision.
- Sharp or burning eye pain.
- A scratchy or gritty feeling in your eye. This can feel like a piece of sand is stuck in your eye.
These side effects can last for up to 2 weeks. Taking folic acid can help reduce them.
What is folic acid?
Folic acid is an important B vitamin that helps your body make new, healthy cells. You may also hear it called folate. Folate and folic acid are 2 forms of the same B vitamin:
- Folate is the natural form. It’s found in foods, such as dark leafy greens, eggs, dairy products, liver, nuts, and beans.
- Folic acid is the man-made form. It’s used in supplements and added to some foods, such as bread, pasta, and breakfast cereals. These are called fortified foods.
You cannot reduce the side effects of your methotrexate injection just by eating folate-rich or fortified foods. You also must take a folic acid supplement.
Here’s why a folic acid supplement works better than food alone:
- It’s easier to absorb. When you eat folate-rich or fortified foods, your body must break them down before it can use them. A folic acid supplement already is in a form your body can absorb and use right away.
- It gives you the same dose (amount) every time you take it. Foods do not have the same amount of folate or folic acid. It’s hard to know how much you’re getting when you eat them. A supplement gives you a steady dose of folic acid, which helps reduce the side effects of your injection.
Buying folic acid supplements
You do not need a prescription to buy folic acid supplements. You can buy them over the counter at your local pharmacy. You also can buy them online at www.gnc.com, www.vitaminshoppe.com, or other websites.
When you read the label, look for either:
- Folic acid 1 mg (1 milligram)
- Folic acid 1,000 mcg (1,000 micrograms)
This is the same amount of folic acid, just written in 2 different ways. You can buy either one.
Taking folic acid supplements
Folic acid supplements often come as tablets or capsules (pills) you swallow.
Take 1 tablet or capsule of folic acid (1 mg or 1,000 mcg) every day. Make sure to take it with a meal. Folic acid works best when you take it with food.
Start taking a folic acid supplement 1 week before your first methotrexate injection. Keep taking it for as long as you get injections. This may be for a few months.
Stop taking your folic acid supplement 1 week after your last methotrexate injection. Your healthcare provider will tell you when your last injection is.
Folic acid supplements and your medicines
Before you start taking a folic acid supplement, tell your healthcare provider about all the medicines you take. This includes prescription and over-the-counter medicines, dietary supplements (such as herbs, vitamins, or home remedies), patches, and creams.
Ask your healthcare provider if it’s safe to take a folic acid supplement with your medicines. Some medicines can react with folic acid supplements and cause problems.
Do not start taking a folic acid supplement before you talk with your healthcare provider.
Medicines for epilepsy
Folic acid supplements can change how well your medicine works if you take medicine for epilepsy (EH-pih-LEP-see), such as:
- Phenytoin (Dilantin®)
- Carbamazepine (Carbatrol®, Epitol®, Equetro®, Tegretol®, Teril®)
- Valproate (Depakote®)
There are other epilepsy medicines, so talk with the healthcare provider who treats your epilepsy. Ask them if it’s safe to take a folic acid supplement with your epilepsy medicine. If it is, they may need to manage your care more while you’re taking the supplement. This may include:
- Checking the amount of epilepsy medicine in your blood more often with blood tests.
- Adjusting (changing) the dose of your epilepsy medicine.
Do not start taking a folic acid supplement before you talk with the healthcare provider who treats your epilepsy.
When to call your healthcare provider
Call your healthcare provider if you:
- Have strong, deep eye pain that aches and does not go away.
- Have vision loss that does not get better with blinking.
- Have blurry vision for more than 1 week after your methotrexate injection.
- Are not sure if a folic acid supplement is safe to take with your medicines.
Learn about our Health Information Policy.
