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Humira and antibodies

My 10 year old daughter started Humira a few months ago after failing Remicade. She's on the 20mg shots every other week and weighs 70 pounds.

Her GI just did a test to see the Humira levels and antibodies and the Humira level came back as 4.2, and usually 5.0 is what is considered a therapeutic level.
As for the antibodies, he said she was borderline on the antibodies at 2.4 (he said 1.7 was normal). I wrote the numbers down but they don't mean anything to me.

He suggested two possible options. Upping her to 40mg instead of the 20mg. Suggesting that she was being under treated and that antibodies can develop in that case (like if someone misses a dose). With the hope that the higher dosage would make her feel better (she's still having symptoms, though not all the time) and help with the antibodies. It feels a bit counter intuitive. That she's displaying some antibodies and that more of the drug could potentially help that instead of making it worse. He would then retest her levels in a month. But of course there is always the risk that the antibodies get worse and she'd have to move on to another drug. On the flip side, if it worked it would avoid having to add yet another heavy duty drug to her medicines.

The other option is adding methotrexate to her current Humira regime.

Does anyone have any experience with Humira and antibodies?

my little penguin

Staff member
The lower levels in the body the more likely to develop antibodies so if she doesn’t have enough humira in her system the body fights it
Higher levels and the body fights it’s less

Methotrexate is a lower level drug but sometimes helps with stopping antibodies from forming other studies state it doesn’t help at all but helps boost the humira
Ds was on humira 40 mg plus mtx at 68 lbs

Dosing got humira is higher for jia kids than crohns
So at 66 lbs they switch to 40 mg
Vs 87 lbs for crohns

They have been using humira much longer in jia
Just a preference
Similarly they use remicade first for crohns kids

Ds was on both remicade for 8 months (reaction. )
Then humira for 5 plus years with mtx for 4 of them

Juvenile Idiopathic Arthritis or Pediatric Uveitis
The recommended dose of HUMIRA for patients 2 years of age and older with polyarticular juvenile idiopathic arthritis (JIA) or pediatric uveitis is based on weight as shown below. MTX, glucocorticoids, NSAIDs, and/or analgesics may be continued during treatment with HUMIRA.

(2 years of age and older)
10 kg (22 lbs) to <15 kg (33 lbs)10 mg every other week
(10 mg Prefilled Syringe)
15 kg (33 lbs) to <30 kg (66 lbs)20 mg every other week
(20 mg Prefilled Syringe)
≥30 kg (66 lbs)40 mg every other week
(HUMIRA Pen or 40 mg Prefilled Syringe)
Second ^ on higher dosing but also it is very, very common to use methotrexate with a Humira or Remicade to prevent the formation of antibodies. After about a year or so, a lot of GI's will consider removing the methotrexate. Both of my girls used methotrexate with Remicade and then stopped after a number of years. The anti tif's have the best track record with pediatric Crohn's so personally I would do whatever I had to in order to prevent antibodies from forming.

Good luck!
We don't have Humira experience, but my daughter had a similar experience with Remicade after she had been on it for 2 years. She was flaring, and when her levels were checked, her Remicade level was on the low side, and her antibody level was detectable (but low) for the first time. We decided to both add methotrexate and increase her Remicade dose, and she responded really quickly to the change. She's continued with Remicade and methotrexate for 3 years since then she hasn't had any more detectable antibodies.


Staff member
I agree - definitely up the dose. The reason she is making antibodies is because there isn't enough of the drug in her blood - or at least, that is how it was explained to us. If her body is metabolizing Humira too fast, you risk having periods of time where there is no Humira in her system and obviously that is not good and can lead to antibody formation. So increasing the dose would benefit her in two ways - 1) She'd have therapeutic levels of Humira in her blood at all times and 2) Because trough levels of the drug would increase, her body is less likely to make antibodies to the drug.

Methotrexate is another option. It is used to prevent antibody formation and/or as a therapy. If it's just for antibodies, then generally a lower dose is given. If it's meant to be a "boost" with Humira because her disease isn't fully controlled, then you'd typically use a higher dose.

Both options are safe...if it were my kiddo, I'd probably increase her Humira dose first, since she is over 66 lbs and clearly has low Humira levels. But MTX is also thought to work by increasing trough levels of the biologic in the blood, so that may work too. Some kids have side effects with MTX, but most tolerate it without issues.

Humira has been used a LOT in the rheumatology world - in kids as young as 2 years old. It's definitely safe, especially since her antibody levels are just barely high. Unlike Remicade, it's a humanized protein so allergic reactions are much rarer than with Remi, which is made with mouse protein.