Question explored with the scientific record
Est-ce que les injections de METHOTREXATE sont dangereuses pour la santé?
Methotrexate is a potent chemotherapy and immunosuppressant drug. Its risks are well documented and dose-dependent. The question is whether the injection route adds specific dangers beyond the oral form.
The evidence retrieved here is almost entirely about using methotrexate injections to treat ectopic pregnancies and certain cancers [1, 2, 3, 4, 5, 6, 9, 10, 12, 13, 18]. That is a very different context from using it for rheumatoid arthritis or psoriasis. In those pregnancy cases, the dose is often a single, targeted injection into the gestational sac, not a weekly systemic injection. The risks reported in those studies are mostly about treatment failure (about 11.5% needed surgery [1]) and the underlying condition, not the injection itself.
For systemic use in autoimmune disease, the evidence here is thin. One meta-analysis from 1992 found methotrexate had a favorable balance of efficacy and toxicity among second-line rheumatoid arthritis drugs [16], but that is old and does not compare injection to oral. A 2025 study on elderly rheumatoid arthritis patients used methotrexate injections plus adalimumab and reported more injection-site reactions (15 vs 2) and more total adverse events (82 vs 65) than methotrexate alone [21]. That tells you the injection site itself can be a problem, but it does not separate methotrexate risk from adalimumab risk.
The specific dangers of methotrexate injections come down to three things. First, the drug itself is toxic to the liver, bone marrow, and lungs, and can cause birth defects. Second, the injection route can cause local skin reactions, pain, and rarely infection at the site. Third, the biggest danger is dosing error: methotrexate is taken once a week for autoimmune conditions, but if taken daily by mistake, it can be fatal. The injection form does not change that risk profile much compared to pills, but it does bypass the gut, which can help people who get nausea from the oral form.
My call: methotrexate injections carry the same serious systemic risks as the oral drug, plus local injection-site reactions. The evidence here does not show that the injection route is more dangerous than the oral route for the same dose, but it also does not include a direct comparison. The real danger is the drug itself, not the needle.
Confidence: moderate. The evidence here is mostly about a different use (ectopic pregnancy) and does not directly compare injection to oral safety for chronic autoimmune therapy.
Sources used 13
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Local Methotrexate Injection as the First-line Treatment for Cesarean Scar Pregnancy: Review of the Literature
This study reviews the outcomes of ultrasound-guided local methotrexate injection as a first-line treatment for cesarean scar pregnancy, finding a success rate of 73.9% after a single injection and an accumulated success rate of 88.5% with additional treatments.
DOI: 10.1016/j.jmig.2015.04.008 -
P06.18: Ectopic pregnancy treated with ultrasound-guided local methotrexate injection
This study evaluates the effectiveness of ultrasound-guided local methotrexate injection for treating ectopic pregnancies, highlighting its advantages over traditional surgical methods and its implications for preserving fertility.
DOI: 10.1002/uog.7095 -
Combined use of uterine artery embolization and local methotrexate injection in interstitial ectopic pregnancies with poor prognosis
This study reports three successful cases of interstitial pregnancies treated with a combination of uterine artery embolization and local methotrexate injection, demonstrating the safety and effectiveness of this approach while preserving ovarian reserve.
DOI: 10.1016/j.fertnstert.2009.03.087 -
EP24.23: Caesarean scar pregnancy: a case report
An intact advanced cervical pregnancy in a 30-year-old woman was diagnosed and managed with laparoscopic dissection, ultrasound-guided potassium chloride injection into the gestational sac, and systemic methotrexate with serial beta-hCG monitoring, resulting in complete resorpti…
DOI: 10.1002/uog.18718 -
ULTRASTRUCTURE OF LIVER IN INHERITED DISORDERS OF FAT OXIDATION
This study presents a new outpatient treatment for ectopic pregnancy involving transvaginal aspiration followed by methotrexate injection, demonstrating its effectiveness and minimal side effects in a case of a left ampullar tubal pregnancy after IVF.
DOI: 10.1016/s0140-6736(87)91752-1 -
Successful management of a triplet heterotopic caesarean scar pregnancy after in vitro fertilization-embryo transfer
This case report details the successful management of a triplet heterotopic caesarean scar pregnancy following in vitro fertilization-embryo transfer, highlighting the use of potassium chloride and methotrexate injections for selective embryo reduction while preserving an intrau…
DOI: 10.1016/j.fertnstert.2010.05.025 -
Delayed diagnosis of a cesarean scar pregnancy: a case report
A single-case report of delayed cesarean scar pregnancy diagnosed at 11 weeks 6 days, treated with local methotrexate injection followed by open laparotomy to remove the gestational sac and trophoblastic tissue, with favorable maternal outcome and emphasis on early diagnosis and…
DOI: 10.1186/s13256-019-1983-1 -
Ectopic Pregnancy in a Caesarean Scar: A Case Report
This case report discusses a rare instance of ectopic pregnancy in a Caesarean scar, highlighting the successful management of the condition through local injection of methotrexate after systemic treatment failed.
DOI: 10.1016/s1701-2163(16)30392-9 -
Conservative approach in unruptured cornual pregnancy with a live fetus
This study presents a case of a 35-year-old woman with an unruptured cornual pregnancy and a live fetus, treated conservatively using transabdominal potassium chloride injection and systemic methotrexate, demonstrating the potential for successful management in similar cases des…
DOI: 10.1016/s0020-7292(97)00133-1 -
Nonsurgical management of unruptured tubal pregnancy with intra-amniotic methotrexate: preliminary report of two cases
This study presents two cases of unruptured tubal pregnancy successfully managed through the aspiration of the pregnancy sac and the injection of methotrexate, demonstrating a potential nonsurgical treatment approach.
DOI: 10.1016/s0015-0282(16)60026-2 -
Use of short‐term efficacy/toxicity tradeoffs to select second‐line drugs in rheumatoid arthritis. A metaanalysis of published clinical trials
This study evaluates the efficacy and toxicity tradeoffs of second-line drugs used in rheumatoid arthritis through a meta-analysis of published clinical trials, concluding that methotrexate and antimalarial drugs offer the best balance of efficacy and safety.
DOI: 10.1002/art.1780351003 -
Intraventricular methotrexate as part of primary therapy for children with infant and/or metastatic medulloblastoma: Feasibility, acute toxicity and evidence for efficacy
A large multicenter prospective study (HIT2000) evaluating intraventricular methotrexate as part of primary therapy for infants and/or metastatic medulloblastoma in children, showing feasible administration with acceptable acute toxicity and suggesting a dose-dependent improveme…
DOI: 10.1016/j.ejca.2015.08.009 -
Long-term efficacy of adalimumab in elderly patients with rheumatoid arthritis and associated risk factors
ADA plus MTX yields superior long-term disease control and functional outcomes compared with MTX alone in elderly rheumatoid arthritis, with identifiable baseline predictors of efficacy and acceptable safety over 24 months.
DOI: 10.62347/wdog7321