Background:As percutaneous coronary intervention (PCI) technologies conferincreasing patient advantage, the use of iodinated contrast media for diagnostic and interventional procedures is increased. Although contrast media obstacles are transient and mild, contrast-induced nephropathy(CIN)negativelyaffects long-term patient mortality. PCI createsa high-risk condition for the incidence of CIN even in patients with a normal renal function. Pentoxifylline (PTX) with a variety of mechanisms may prevent CIN.We soughtto assess the positive effect of PTX administration at the beginningprior to contrast media use to 24 hours after PCI to prevent CIN inpatients withSTEMI.Methods:In this double-blind, single-center,clinical trial, we randomly assigned 296 consecutive patients to the control group (n=148) without PTX and the case group (n=148) with PTX 400mg/tid at the time of hospitalization to 24 hours after the procedure. Serum creatinine was measured before and 48 hours after the procedure. The occurrence of CIN within48 hours was our end point. CIN was defined as a 0.5 mg/dLincrease or more in serum creatinine or a 25% increase or more above baseline serum creatinine.Results:A total of 296 patients were enrolled in this trial and were randomly assigned to receive either primary PCI plus PTX or only primary PCI. Out of 148 patients who receivedPTX,only 12.2% were seen to have CIN incidence (>0.5mg/dLor a 25% increase intheCr level);however,the difference between the 2groups regarding CIN was not significant (P=0.4). Out of the 296 patients,only 20 were found to havechronic kidney disease (CKD)(CKD wasdefined as baseline Cr>1.5);and of those patients,3(15%) showed CIN incidence. Nevertheless,the difference between the 2groupsregarding CIN incidence was not significant (P=0.7). The regression test showed that between all confounding factors in the 2groups of PTXpositive and negative, sex and ejection fractionhad positive effectsonthe rise in theCr level and,consequently,theincidence of CIN (95% CI: 1.60 to 30.85; P=0.01 and95%CI:0.92 to 1; P=0.05). Conclusions:Administration of oral PTX to patients with increased risk for CIN scheduled for primary PCI may not reduce the Cr level and thus the occurrence of CIN. Given thehigher prevalence of hypotension inthepatients without PTX, higher prevalence of CKD in the patients without PTX,and absence of significant difference between the 2groups regarding the incidence of CIN, PTX had nopreventive effect onCIN occurrence in STEMI. Among all factors influencingCIN occurrence,sex and ejection fraction hadpositive effects on the rise in the Cr level.(Iranian Heart Journal 2015; 16(4): 28-34)