Methotrexate Increases Serum Calcium Levels in Patients with Rheumatoid Arthritis: A Retrospective Study at a Referral Hospital in Indonesia.

Background: Rheumatoid arthritis (RA) is a significant issue, particularly in bone health problems, because it can prolong diseases like secondary osteoporosis. Subsequently, the anchor of drug therapy for RA is methotrexate (MTX), which also has the potential to reduce the risk of secondary osteoporosis. Objective: This study aims to examine the effect of MTX on calcium levels, an important parameter for monitoring bone health and the risk of secondary osteoporosis in patients with RA. Methods: A retrospective study was carried out by collecting data from the medical records of patients, which included demographic and patient characteristics, treatment data (drug and dosage), duration of treatment, and calcium levels. All patients were diagnosed with RA and fell within the age range of 18 to 59 years. Additionally, the effectiveness of MTX therapy was compared with other treatments, categorizing patient data accordingly. Statistical analyses, such as χ2 and ordinal regression, using IBM-SPSS Statistics version 25 (IBM-SPSS Inc, Armonk, New York) were used to establish associations between MTX treatment and calcium levels, reporting odds ratio and 95% CI values. Results: The data consisted of 123 patients with RA, comprising 99 who had a history of MTX use for more than 6 months and 24 who either did not use MTX or used it for <6 months. The majority of patients were women and their ages ranged between 40 and 59 years. MTX monotherapy was the most used with a dose range of 7.5 to 15 mg. Furthermore, this study observed that patients treated with MTX between 7.5 and 15 mg have lower serum calcium levels than those who received 17.5 to 25 mg (P = 0.022; odds ratio = 5.663; 95% CI, 0.251-3.218). Most patients with RA using MTX maintained normal calcium levels. No significant differences were observed between single MTX therapy and combination therapy. Conclusions: Although further investigation is needed, this study showed the potential properties of MTX in maintaining patients' serum calcium levels, which may help to reduce the risk of secondary osteoporosis in patients with RA.