Dupixent contains dupilumab, a lab-made human antibody designed to block a specific part of the immune system that drives allergic inflammation. Beyond the active ingredient, each pre-filled syringe includes a handful of inactive ingredients that keep the protein stable and ready for injection. Here’s a full breakdown of what’s inside.
The Active Ingredient: Dupilumab
Dupilumab is a fully human monoclonal antibody, meaning it’s a protein engineered to mimic the antibodies your immune system naturally produces. It belongs to a class called immunoglobulin G4 (IgG4), and its specific target is a receptor on cells called IL-4 receptor alpha (IL-4Rα).
This receptor is a shared gateway for two inflammatory signaling molecules, IL-4 and IL-13, that play a central role in allergic and eosinophilic inflammation. By physically blocking the receptor, dupilumab prevents both signals from getting through. That’s what makes it useful across a range of conditions driven by the same underlying type of inflammation, from eczema to asthma to nasal polyps.
Inactive Ingredients in Each Syringe
Antibodies are fragile proteins. Without the right chemical environment, they can break down, clump together, or lose effectiveness before you ever inject them. The inactive ingredients in Dupixent exist to prevent that. For the 300 mg pre-filled syringe (delivered in 2 mL of liquid), the full list is:
- Sucrose (100 mg) acts as a stabilizer, protecting the antibody protein during storage and keeping it from degrading.
- L-arginine hydrochloride (10.5 mg) helps prevent the protein molecules from clumping together.
- L-histidine (6.2 mg) serves as a buffer to maintain the solution at a consistent pH of 5.9, which is the sweet spot for dupilumab’s stability.
- Polysorbate 80 (4 mg) is a surfactant that protects the protein from damage during handling and shipping, particularly from the shaking and agitation that can break down antibodies.
- Sodium acetate (2 mg) works alongside L-histidine as an additional pH buffer.
- Water for injection makes up the rest of the liquid volume.
The 200 mg syringe contains the same ingredients in slightly different amounts, delivered in a smaller 1.14 mL volume. None of these inactive ingredients are unique to Dupixent. They’re standard components in injectable biologic medications.
How Dupilumab Works in the Body
Your immune system uses signaling molecules called interleukins to coordinate inflammatory responses. In conditions like atopic dermatitis, asthma, and eosinophilic esophagitis, two of these signals, IL-4 and IL-13, are overactive. They trigger a cascade that produces excess inflammation, mucus, itching, and tissue damage.
Both IL-4 and IL-13 need the same receptor subunit (IL-4Rα) to deliver their messages to cells. Dupilumab binds to that shared subunit and blocks it. This shuts down signaling from both molecules at once, rather than targeting just one. The result is a broad dampening of the type of inflammation (called Th2 or type 2 inflammation) responsible for these conditions.
The blocking can work in multiple ways: it may prevent IL-4 from attaching to the receptor, stop the receptor from assembling properly when IL-13 binds, or both. Regardless of the exact mechanism at the molecular level, the practical effect is the same. The overactive allergic response calms down over weeks of treatment.
Available Forms and Doses
Dupixent comes as a clear to slightly yellow liquid in two delivery formats: a pre-filled syringe and a pre-filled pen (auto-injector). Both are single-dose devices meant for injection under the skin, typically in the thigh or abdomen. Three dose strengths are available:
- 100 mg pre-filled syringe (for younger or smaller pediatric patients)
- 200 mg pre-filled syringe or pre-filled pen
- 300 mg pre-filled syringe or pre-filled pen
The dose and injection frequency depend on the condition being treated, the patient’s age, and body weight. Most adults with atopic dermatitis or asthma use the 300 mg or 200 mg dose every two weeks after an initial loading dose.
What Dupixent Is Approved to Treat
Because IL-4 and IL-13 drive inflammation in many different tissues, Dupixent has accumulated an unusually broad list of FDA-approved uses. As of 2025, it is approved for eight conditions:
- Atopic dermatitis (eczema) in patients 6 months and older with moderate to severe disease
- Asthma in patients 6 years and older with moderate to severe eosinophilic asthma or oral steroid-dependent asthma
- Chronic rhinosinusitis with nasal polyps in patients 12 and older
- Eosinophilic esophagitis in patients 1 year and older weighing at least 15 kg (about 33 pounds)
- Prurigo nodularis in adults
- Chronic obstructive pulmonary disease (COPD) in adults with an eosinophilic phenotype
- Chronic spontaneous urticaria (hives) in patients 12 and older
- Bullous pemphigoid in adults
Common Side Effects
Because dupilumab targets a narrow part of the immune system rather than suppressing it broadly, its side effect profile is relatively mild compared to older immunosuppressants. In clinical trials, the most frequently reported reactions were nasopharyngitis (common cold symptoms) at 28.1%, conjunctivitis (eye inflammation or redness) at 19.5%, flare-ups of atopic dermatitis at 16.4%, upper respiratory infections at 13.1%, and injection site reactions at 9.7%.
The conjunctivitis finding is notable because it appears more often with Dupixent than with placebo, and it can be persistent enough to need treatment with eye drops. Injection site reactions, including redness, swelling, or itching at the injection spot, are generally mild and tend to decrease over time.
Storage Requirements
Dupixent should be kept refrigerated between 36°F and 46°F (2°C to 8°C). If needed, you can take it out and store it at room temperature up to 77°F (25°C) for a maximum of 14 days. Any syringe or pen left out longer than 14 days should be discarded, even if it looks normal. The medication should never be frozen or exposed to direct heat or sunlight.