Higher body mass index is associated with a lower iloprost infusion rate tolerance and higher iloprost-related adverse events in patients with systemic sclerosis

Background: Systemic sclerosis (SSc) is an autoimmune disease characterized by vasospasm and microvascular involvement. Iloprost (ILO), a prostaglandin analogous, is used for the treatment of SSc-related Raynaud's phenomenon and digital ulcers. The suggested dose is 0.5-2 ng/kg/min for 6-8 h, and the maximum dose is decided upon the patient's tolerance. Objectives: This study aims to analyze ILO infusion tolerance and possible predictive factors in patients with SSc. Design: This is a retrospective observational study. Method: We evaluated 113 patients with SSc beginning ILO intravenous (IV) infusion treatment between 2004 and 2021. We assessed the maximum tolerated ILO IV infusion rate, the incidence of adverse events (AEs), and the need for symptomatic therapy during the dose-finding sessions. We collected relevant demographic and medical and employed generalized linear models to assess possible predictors of maximum tolerated ILO infusion rate and AEs and logistic regression to assess predictors of AEs. Results: The median ILO infusion rate at the end of the dose-finding process was 0.88 ng/kg/min [interquartile range (IQR) = 0.37]. We found a significant inverse correlation between ILO infusion rate and body mass index (BMI) at the beginning of treatment. BMI was negatively associated with ILO infusion rate (β = -0.21, p = 0.02) after correction for relevant confounding factors. Overweight patients (BMI >26) presented a 13-fold increased risk of developing AEs during ILO titration [adjusted odds ratio = 13.979, 95% confidence interval (CI) = 2.359-82.845]. AEs during ILO titration occurred in 47.8% of patients, of whom 22.2% presented hypotension. Other AEs were headache, nausea, vomiting, diarrhea, and edema. Symptomatic therapy was needed in half of the patients at least once. Conclusion: This study showed that higher BMI was statistically associated with lower ILO infusion rate tolerance and higher AEs rate, underlying a possible BMI-dependent endothelial dysfunction. Individual ILO regimens still need to be tailored to the patient. Plain language summary: Introduction: Systemic sclerosis is a rare a rheumatic disease characterized by skin thickening, vasospasm, and digital ulcers (DUs), as well as other organs involvement. Iloprost, which is administered as intravenous infusion, is one of the main treatments for this disease, and it is effective in reducing vasospasm and the frequency of DUs. Even if there is a suggested dose range, the exact dose must be tailored on each patient, because the tolerance to the drug is variable. Tolerance is limited by dose-dependent unwanted effects, as headache, low blood pressure, dizziness, and sickness. This study aimed to identify possible predictors of such tolerance.Materials and Methods: We collected data from our patients with systemic sclerosis beginning the treatment with iloprost between January 2004 and November 2021 at our hospital facility in Verona, Italy, and analyzed different factors that could be associated with a better tolerance, as age, sex, disease duration, smoking habit, body mass index (a measure of body fatness), blood pressure, concomitant medications, and different patterns of the disease.Results: We found that a higher body mass index was associated with lower iloprost tolerance and higher adverse events rate in patients with systemic sclerosis, while we did not find a correlation with other factors. We believe overweight and obese patients (who have a higher body mass index) have a defect in the vasodilatation mechanism and can therefore be more susceptible to the effect of this medication.Conclusions: While preliminary, our results could provide a good starting point to develop a predictive tool to limit adverse events during this therapy.