If you have ankylosing spondylitis (AS), you might have heard of tumor necrosis factor (TNF). It’s a type of protein in your body that causes inflammation. If your immune system goes into overdrive and causes you to have high levels of TNF in your blood, that leads to inflammation in your joints and ligaments. This is what causes AS symptoms like pain, stiffness, and swelling along the spine and other joints.
TNF inhibitors are drugs designed to suppress the immune system, target TNF, and lower inflammation in your joints. The aim is to prevent joint damage in the long run. You may also hear your doctor refer to this class of drugs as TNF blockers, biologics, or anti-TNF drugs.
TNF inhibitors that are FDA-approved for use include:
- Adalimumab (Humira)
- Certolizumab pegol (Cimzia)
- Etanercept (Enbrel)
- Golimumab (Simponi)
- Infliximab (Remicade)
How Do TNF Inhibitors Work?
TNF inhibitors are not like painkillers you might take for a headache. They’re designed to act as antibodies and specifically target the TNF protein. They stabilize an overactive immune system and block TNF production. This may make it harder for your body to fight an infection. But it lowers the inflammation in your joints that causes arthritis-like symptoms.
They’re given to you if nonsteroidal anti-inflammatory drugs (NSAIDs) like naproxen and ibuprofen don't help. Not all TNF inhibitors might work for you. Doctors find that some people respond well to one medication but not another. It’s hard to predict which one might work for you. Your doctor will try a trial and error approach to find the drug that’ll suit you best.
For example, you might use one type of TNF blocker and not see any results or improvement. But 6 months later, your doctor might put you on a different type of drug and it might work just fine.
How Do You Take INF Inhibitors?
You can take TNF inhibitors as an injection under the skin or as an infusion your doctor gives directly into your veins. This will depend on the type of drug your doctor prescribes.
If you’re taking it as an injection, you don’t have to go to a doctor’s office. You can take it at home. Drugs you can inject include adalimumab, certolizumab, and etanercept. You’ll need to inject it in your thigh or stomach. Your doctor, a nurse, or a pharmacist can teach you how to do it. Make sure you change the injection site each time and don’t use the same spot too many times.
You’ll get golimumab and infliximab as infusions through a drip into a vein. This is called intravenous infusion. You’ll need to take this at a doctor’s office or an infusion center. The entire treatment can take up to 4 hours. Usually, you’ll get 2 hours of the drip and your doctor will ask you to stay for an extra 2 hours to make sure you don’t have serious side effects.
You’ll need a new dose every 2 weeks. After you’ve had the infusions for a while, the treatments will take less time.
You can take most of these drugs alone. But in some cases, your doctor might give it to you along with other medications such as hydroxychloroquine, leflunomide, methotrexate, prednisone, or sulfasalazine.
What Are the Benefits of TNF Inhibitors?
Studies show that if you have AS and you take TNF inhibitors for up to 24 weeks, they can:
- Lower pain
- Improve function in your joints
- Increase your odds for a reduction of AS symptoms like morning stiffness and swelling
- Lower inflammation around your spine
- Slow down joint damage
Most people start to notice their symptoms improve within two to three doses. But it might take up to 3 months to see the full benefits.
What Are the Side Effects?
Most people tolerate INF inhibitors well and only have minor side effects. But over 1 in 10 people on average have serious side effects.
The most common concern with TNF inhibitors is that they can increase your chances of tuberculosis infection (TB). It’s a bacterial infection that causes a serious type of lung infection. The bacteria spreads easily through droplets released when you sneeze or cough. To avoid this, your doctor will screen you for TB before they give you the drugs.
Another common side effect is that TNF blockers increase the odds of serious infections from common bugs like the flu, common cold, pneumonia, and skin infections. To avoid this, your doctor might give you a round of antibiotics to knock it out of your system before they prescribe anti-TNF drugs.
In some cases, TNF inhibitors can also increase your risk for nonmelanoma skin cancer. To rule this out, you’ll be screened for potential skin cancers.
Other side effects can include:
- Injection site reaction on the skin. This can look like an itchy, red welt or bump that can last up to a week.
- Reaction near or around the route you get an infusion
- Lip swelling
- Breathing trouble
- Low blood pressure
- Liver inflammation (transaminitis)
- Upper respiratory tract infections
- Throat inflammation (pharyngitis)
- Belly pain
If you notice these side effects, tell your doctor. They may try another drug to see if it works better for you.
Who Shouldn’t Take TNF Inhibitors?
TNF blockers are not suitable for everyone. Your doctor won’t prescribe TNF inhibitors to you if:
- You’re breastfeeding.
- You have an infection.
- You have a history of lupus or multiple sclerosis.
- You have cancer or precancerous cells.
- You have a history of heart disease.
However, you can take these drugs if you have basal cell carcinoma (a type of skin cancer). You can also take them if you’ve had cancer that was treated more than 10 years ago.
Studies also show that you can safely use TNF inhibitors during pregnancy. But some of the drugs, especially adalimumab, golimumab, and infliximab, are able to pass to the baby through the placenta, especially during second or third trimesters. If you’re planning to get pregnant and have AS, talk to your rheumatologist, a doctor who specializes in arthritis-related conditions, about it.
They may suggest certolizumab, a TNF inhibitor you take by injection. Studies have shown that this medication doesn’t cross the placenta.