DMARDs, short for disease-modifying antirheumatic drugs, are medications that slow or stop the immune system from attacking the body’s own joints and tissues. Unlike painkillers, which only mask symptoms, DMARDs change the underlying course of diseases like rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. They come in three broad categories with very different mechanisms and cost profiles, and the strategy for using them has evolved considerably over the past two decades. How they work, when doctors switch between them, and what risks they carry are all questions worth unpacking.
The Three Categories
DMARDs fall into three groups, and the labels matter because they determine how you take the drug, what it costs, and what side effects to watch for. Conventional synthetic DMARDs (csDMARDs) are the oldest group and include methotrexate, sulfasalazine, hydroxychloroquine, and leflunomide. These are pills, they have been around for decades, and they are cheap relative to the newer options. Methotrexate is still the first drug most rheumatologists reach for when treating rheumatoid arthritis.
Biologic DMARDs (bDMARDs) are large protein molecules made from living cells. They target specific parts of the immune system, most commonly tumor necrosis factor (TNF), interleukins like IL-17 and IL-23, or B cells. Because they are proteins, they cannot survive digestion and are given by injection or infusion. They are far more expensive than conventional DMARDs and carry distinct infection risks. TNF inhibitors like adalimumab, etanercept, and infliximab are the most widely prescribed biologics in rheumatology.
Targeted synthetic DMARDs (tsDMARDs) are the newest group. The most prominent are Janus kinase (JAK) inhibitors such as tofacitinib and upadacitinib. Unlike biologics, these are small molecules taken as pills. They block signaling inside cells rather than intercepting a single protein outside the cell, which gives them a broader reach across multiple inflammatory pathways.1Indian Journal of Dermatology, Venereology and Leprology. JAK-STAT inhibitors in Immune mediated diseases: An Overview
How They Work
Each category has a fundamentally different mechanism. Methotrexate, the workhorse of csDMARDs, was originally developed as a cancer drug but works at much lower doses in arthritis. Its anti-inflammatory action is most commonly attributed to raising levels of adenosine, a molecule that, when it binds to receptors on immune cells, triggers a cascade that dials down inflammation broadly.2PubMed Central. Methotrexate mechanism in treatment of rheumatoid arthritis That broad effect is partly why methotrexate remains useful even as newer, more targeted drugs have appeared.
TNF inhibitors, the most established biologics, work by physically blocking TNF from latching onto its receptors on cell surfaces. TNF is one of the main alarm signals that drives joint inflammation. The biologic drug binds to TNF or to its receptor, preventing the two from meeting, which silences a major inflammatory signaling chain.3The Journal of Rheumatology. Tumor Necrosis Factor and Anti-Tumor Necrosis Factor Therapies Other biologics use the same principle but target different alarm signals: IL-17 inhibitors, IL-23 inhibitors, and the B-cell depleter rituximab each intercept a different part of the immune response.
JAK inhibitors take a different approach entirely. Instead of blocking a protein outside the cell, they enter the cell and interfere with the JAK-STAT signaling pathway, which is used by many different cytokines to relay messages from the cell surface to the nucleus. By blocking this pathway, JAK inhibitors can suppress the effects of multiple inflammatory signals at once, rather than one at a time.4Indian Journal of Dermatology, Venereology and Leprology. JAK-STAT inhibitors in Immune mediated diseases: An Overview That broader reach is a double-edged sword: it may help some patients who do not respond to a single-target biologic, but it also means more immune pathways are being dampened.
What DMARDs Treat
Rheumatoid arthritis is the flagship condition for DMARDs, but the same drugs are now used across a range of autoimmune and inflammatory diseases. Psoriatic arthritis, where joint inflammation accompanies psoriasis, is treated with an overlapping but not identical set of DMARDs. A recent systematic review cataloguing the drug pipeline found 44 DMARDs in clinical development for psoriatic arthritis alone, including conventional synthetics, biologics targeting IL-17, IL-23, and TNF, and several JAK inhibitors.5RMD Open. The 2023 pipeline of disease-modifying antirheumatic drugs (DMARDs) in clinical development for spondyloarthritis (including psoriatic arthritis): a systematic review of trials Ankylosing spondylitis (axial spondyloarthritis) has a similarly large pipeline, with IL-17 inhibitors emerging as a major focus.
Beyond joint diseases, some DMARDs have found uses in inflammatory bowel disease, lupus, vasculitis, and certain skin conditions like alopecia areata and atopic dermatitis. JAK inhibitors in particular have expanded rapidly outside rheumatology because so many inflammatory diseases rely on the same JAK-STAT pathway.6Indian Journal of Dermatology, Venereology and Leprology. JAK-STAT inhibitors in Immune mediated diseases: An Overview
The Treat-to-Target Strategy
Modern rheumatology does not just prescribe a DMARD and hope for the best. The standard approach is called “treat to target,” meaning the doctor sets a measurable goal, usually remission or very low disease activity, and adjusts therapy at regular intervals until that goal is met. In a Dutch study of patients with very early rheumatoid arthritis treated under this protocol, about half achieved remission within six months and close to 60% achieved it by one year. Most patients in that cohort also avoided meaningful joint damage on X-rays.7PubMed. Implementation of a treat-to-target strategy in very early rheumatoid arthritis: results of the Dutch Rheumatoid Arthritis Monitoring remission induction cohort study
What makes this approach powerful is its speed. When a patient starts methotrexate and is not in remission after three to six months, the rheumatologist does not wait years before changing course. Instead, the regimen is stepped up, either by adding another conventional DMARD, adding a biologic, or switching to a different mechanism entirely. Early, aggressive treatment consistently outperforms a wait-and-see approach in terms of preventing irreversible joint erosion.
Combination Therapy and Why Methotrexate Stays Central
Methotrexate’s staying power is not just about its effectiveness alone. It also works as a foundation that improves the performance of other drugs when used in combination. A systematic review and network meta-analysis found that combining a biologic with methotrexate produced a meaningfully better response than using either drug by itself, with roughly 20 to 57% higher odds of achieving a 50% improvement in symptoms depending on the specific biologic.8PubMed Central. Comparative Effectiveness of Combining MTX with Biologic Drug Therapy Versus Either MTX or Biologics Alone for Early Rheumatoid Arthritis in Adults: a Systematic Review and Network Meta-analysis A separate meta-analysis of randomized trials found that adding methotrexate to a biologic increased the likelihood of a good response by about a third compared to the biologic alone.9PubMed. Added value of combining methotrexate with a biological agent compared to biological monotherapy in rheumatoid arthritis patients: A systematic review and meta-analysis of randomised trials
One reason methotrexate boosts biologic effectiveness relates to immunogenicity, which is discussed below. But an even more practically relevant finding comes from Cochrane review evidence suggesting that “triple therapy,” the combination of methotrexate with sulfasalazine and hydroxychloroquine, performs comparably to methotrexate plus a biologic for controlling disease activity. Given that triple therapy costs a fraction of the price, the Cochrane authors argued it is hard to justify jumping straight to biologics before trying this combination.10Cochrane Database of Systematic Reviews. Methotrexate alone or in combination with other medications for rheumatoid arthritis This is a point of genuine debate in rheumatology, with some clinicians pushing for early biologic use and others advocating for the cheaper conventional combination first.
Infection Risk and Screening
All DMARDs suppress parts of the immune system, so all of them raise infection risk to some degree. The practical question is how much and what kind. Biologics carry a modestly higher risk of serious infections compared to conventional DMARDs. JAK inhibitors have a similar overall risk of serious infection to biologics, with one notable exception: they come with a substantially increased risk of herpes zoster (shingles), especially in patients also taking glucocorticoids.11PubMed Central. Risk for infections with glucocorticoids and DMARDs in patients with rheumatoid arthritis
An important practical detail: high-dose glucocorticoids (steroids like prednisone) carry the greatest infection risk of all, including the risk of opportunistic infections that healthy immune systems would normally handle easily. Even low-dose glucocorticoids increase infection risk at a level comparable to biologics.12PubMed Central. Risk for infections with glucocorticoids and DMARDs in patients with rheumatoid arthritis This means patients who are using prednisone “just to get by” while waiting for their DMARD to kick in may actually be taking on more infection risk than the DMARD itself would cause.
Before starting biologic or targeted synthetic DMARDs, screening for latent tuberculosis and hepatitis B is standard practice, and the 2022 EULAR recommendations suggest considering the same screening even before conventional DMARDs and glucocorticoids.13Annals of the Rheumatic Diseases. 2022 EULAR recommendations for screening and prophylaxis of chronic and opportunistic infections in adults with autoimmune inflammatory rheumatic diseases For hepatitis B, the concern is viral reactivation during immune suppression, and patients who test positive for certain hepatitis B markers need periodic monitoring even if they have no active infection.14RMD Open. Systematic literature review informing the 2022 EULAR recommendations for screening and prophylaxis of chronic and opportunistic infections in adults with autoimmune inflammatory rheumatic diseases
When Biologics Stop Working
A frustrating reality with biologic DMARDs is that many patients eventually lose their response. When researchers tracked the reasons people with rheumatoid arthritis discontinued biologics, the most common was inadequate response (about 43%), followed by loss of efficacy over time (about 26%), and side effects (about 14%).15PubMed Central. Reasons for multiple biologic and targeted synthetic DMARD switching and characteristics of treatment refractory rheumatoid arthritis So some patients never respond well in the first place, and others respond initially but gradually lose the benefit.
One major driver of this loss is the body’s own immune response against the drug. Because biologics are large foreign proteins, the immune system can generate anti-drug antibodies that neutralize the medication. In a study tracking this problem across multiple biologics, patients who developed persistent anti-drug antibodies had only about a 46% chance of responding to treatment at 12 months, compared to 83% for patients who did not develop those antibodies.16JAMA Network Open. Response to Biologic Drugs in Patients With Rheumatoid Arthritis and Antidrug Antibodies TNF inhibitors are the most common culprits, partly because they are the most widely used biologics and partly because of their molecular characteristics.17PubMed Central. Anti-Drug Antibodies in the Biological Therapy of Autoimmune Rheumatic Diseases This is one of the reasons methotrexate is so often co-prescribed with biologics: by suppressing the immune system slightly, methotrexate reduces the formation of anti-drug antibodies.
When a biologic fails, there are two strategies. “Cycling” means switching to another drug within the same class, like moving from one TNF inhibitor to a different TNF inhibitor. “Swapping” means changing to a drug with a completely different mechanism, like moving from a TNF inhibitor to an IL-6 inhibitor or a JAK inhibitor. Research suggests swapping is the better bet: one study found that cycling doubled the risk of subsequent treatment failure compared to swapping.18PubMed Central. Primary non-response in inflammatory arthritis treated with biologics and targeted therapies in daily clinical practice If the immune system failed to respond to one TNF blocker, it may well fail to respond to a different one that works the same way.
Biosimilars and What They Mean for Patients
As the original biologic DMARDs have lost patent protection, biosimilars have entered the market at lower prices. A biosimilar is not a generic in the traditional sense. Because biologics are made from living cells, no two manufacturing processes produce exactly identical molecules. Biosimilars are instead shown to be highly similar to the original drug with no clinically meaningful differences. This distinction causes understandable anxiety among patients who are switched from a brand-name biologic to a biosimilar.
The evidence on switching is reassuring. A systematic review of available switching data found no major issues with efficacy, safety, or immunogenicity when patients moved from a reference biologic to its biosimilar.19PubMed Central. The Efficacy, Safety, and Immunogenicity of Switching Between Reference Biopharmaceuticals and Biosimilars: A Systematic Review A network meta-analysis of TNF inhibitor biosimilars in rheumatoid arthritis specifically found that switching produced equivalent results on standard measures of treatment response and disability, and the rates of side effects, discontinuation, and anti-drug antibodies were comparable between groups.20Scientific Reports. Impact of switching between reference biologics and biosimilars of tumour necrosis factor inhibitors for rheumatoid arthritis: a systematic review and network meta-analysis If your insurer or rheumatologist suggests switching to a biosimilar, the evidence does not support resisting that change on efficacy grounds.
Vaccines and DMARDs
If you are on a DMARD, vaccine effectiveness is a practical concern. The answer depends heavily on which drug you are taking. A meta-analysis found that methotrexate reduces the immune response to pneumococcal vaccines and may impair the response to influenza vaccines. Rituximab, the B-cell depleting biologic, reduces the response to both. But anti-TNF biologics did not significantly impair vaccine responses in the same analysis.21PubMed. Effect of methotrexate, anti-tumor necrosis factor α, and rituximab on the immune response to influenza and pneumococcal vaccines in patients with rheumatoid arthritis: a systematic review and meta-analysis
The practical takeaway is that rheumatologists often recommend timing vaccinations strategically, particularly with rituximab, where vaccines ideally should be given before the next infusion cycle, when B-cell counts have partially recovered. For methotrexate, some guidelines suggest holding the drug for a week or two around vaccination to improve the immune response, though this decision involves balancing the risk of a brief disease flare against the benefit of better vaccine protection. Live vaccines are generally contraindicated on any immunosuppressive DMARD, which means patients need inactivated alternatives where available.
Surgery and DMARD Timing
Patients on DMARDs who need surgery face a balancing act: stopping the drug too early risks a disease flare, but continuing it through surgery may impair wound healing or raise infection risk. Updated German rheumatology recommendations give a practical framework. Conventional DMARDs like methotrexate can usually be continued, though high methotrexate doses may be reduced to 15 mg per week or less. Leflunomide may need a washout in patients at high infection risk. For biologics, surgery is best scheduled at the end of a treatment interval, when drug levels are at their lowest. JAK inhibitors should be paused for three to four days before major procedures. In all cases, restarting treatment as soon as wound healing allows is a priority.22PubMed. Perioperative management of patients with inflammatory rheumatic diseases: Updated recommendations of the German Society for Rheumatology
Pregnancy and DMARDs
For people of childbearing age, DMARD safety during pregnancy is a high-stakes question. The evidence base is uneven. There is moderate evidence supporting relatively consistent recommendations for conventional DMARDs in pregnancy, but the guidance for biologics and JAK inhibitors is much thinner and varies between guidelines.23PubMed Central. Recommendations for the Use of Disease-Modifying Antirheumatic Drugs in Pregnancy and Reproductive Health for Patients With Rheumatic Disease: A Scoping Review Methotrexate and leflunomide are clearly contraindicated in pregnancy due to established risks of birth defects. Hydroxychloroquine and sulfasalazine are generally considered compatible with pregnancy and are the conventional DMARDs most commonly continued. Among biologics, certain TNF inhibitors like certolizumab (which does not cross the placenta efficiently) are often favored when biologic therapy is needed during pregnancy, though the decisions are individualized and evolving.
Cost, Access, and Insurance Barriers
The cost gap between DMARD categories is enormous. A month of methotrexate can cost under $50, while a month of a biologic or JAK inhibitor can run $3,000 to $6,000 or more before insurance. Biosimilars have brought prices down somewhat, but they remain far more expensive than conventional synthetics.
Insurance design directly affects outcomes. A study of patients with rheumatoid or psoriatic arthritis found that those whose plans required step therapy, meaning they had to try and fail a cheaper drug before the insurer would cover a biologic, had lower odds of treatment effectiveness. The reduction was about 19% for rheumatoid arthritis and 27% for psoriatic arthritis, driven largely by lower medication adherence when administrative barriers delayed access.24PubMed Central. Impact of Plan-Level Access Restrictions on Effectiveness of Biologics Among Patients with Rheumatoid or Psoriatic Arthritis In other words, making patients jump through hoops did not save the system money in a clinically neutral way; it actually made treatment less likely to work. For Medicare beneficiaries specifically, biologic costs are often shifted heavily to the patient, putting these drugs out of financial reach for some.25PubMed. Impact of Medicare Part D on access to and cost sharing for specialty biologic medications for beneficiaries with rheumatoid arthritis
Predicting Who Will Respond
One of the most frustrating aspects of DMARD therapy is that the choice of drug is still largely trial and error. Only about 50 to 60% of patients with psoriatic arthritis show a satisfactory response to their first-line DMARD.26PubMed. Emerging molecular biomarkers for predicting therapy response in psoriatic arthritis: A review of literature In rheumatoid arthritis, the numbers are not much better. Researchers are working to develop biomarkers that could predict before treatment begins which patients will respond to which drugs.
The most promising recent work involves analyzing tissue from the synovial lining of the joint. In one randomized trial, detailed molecular analysis of biopsies from 164 patients allowed researchers to predict in advance who would respond to rituximab versus tocilizumab, two biologics that target different parts of the immune system.27PubMed Central. Toward pre-treatment prediction of biologic DMARD response in RA Blood-based biomarkers, including inflammatory markers, autoantibodies, and genetic signatures, are also under investigation, though none has yet become reliable enough for routine clinical use.28PubMed Central. Biomarkers to Predict DMARDs Efficacy and Adverse Effect in Rheumatoid Arthritis For now, picking the right DMARD remains a process of informed guessing followed by systematic adjustment, which is exactly why the treat-to-target approach with regular reassessment exists.
A Brief History of How DMARDs Emerged
The concept of modifying the disease course rather than just treating pain is relatively recent in the long history of arthritis care. Gold salts, first used for rheumatoid arthritis in 1929, were among the earliest DMARDs. About half of patients initially achieved remission on gold therapy, but the drug fell out of favor because of serious side effects.29Reumatologia. Evolving strategies in the treatment of rheumatoid arthritis: a historical perspective Methotrexate, repurposed from cancer treatment, became the standard in the 1980s and 1990s. The first biologic DMARDs arrived around the turn of the millennium, and JAK inhibitors followed in the 2010s. Each wave added options, but none has made the earlier drugs obsolete: methotrexate remains the backbone of treatment for most patients starting therapy today.
Mortality and Long-Term Safety
Whether newer DMARDs affect lifespan is an understandable concern for patients who may take these drugs for decades. A systematic review and meta-analysis comparing mortality in patients on biologic or targeted synthetic DMARDs versus those on conventional DMARDs found no significant overall increase in death rates. About 2.7% of patients on biologics or targeted synthetics died during study follow-up periods, compared to about 2.9% on conventional DMARDs. However, when the researchers looked specifically at anti-TNF users, there was a modest but statistically significant increase in mortality risk compared to non-biologic users.30PubMed Central. Biologic DMARDs and targeted synthetic DMARDs and the risk of all-cause mortality in rheumatoid arthritis: A systematic review and meta-analysis This finding deserves some context: the patients placed on anti-TNF therapy often have more severe disease to begin with, making direct comparisons tricky. Still, the overall picture is that modern DMARDs do not appear to carry a large mortality penalty, and for many patients the risk of uncontrolled disease almost certainly outweighs the risk of treatment.