The aim of this study was to assess whether intravenous dexamethasone was noninferior to perineural dexamethasone as an adjuvant to ropivacaine for a combination of saphenous and sciatic nerve blocks in patients undergoing foot and ankle surgery.This was a prospective, blinded, randomized noninferiority study. Seventy-five patients, aged 18-75 years, with an American Society of Anesthesiologists (ASA) physical status I-III who underwent foot and ankle surgery were involved. Patients scheduled for ultrasound-guided popliteal sciatic nerve block and saphenous nerve block were randomized to receive 0.375% ropivacaine with 7.5 mg of dexamethasone perineurally (Dex-PN), 10 mg of dexamethasone intravenously (Dex-IV) or neither (Placebo). The primary outcome was the duration of analgesia. The major secondary outcomes were the composite pain intensity and opioid consumption score at 0-48 h intervals after anesthesia.The mean analgesic duration was 26.2 h in the Dex-IV group and 27.9 h in the Dex-PN group (duration difference, -1.7; 95% CI, -3.8 to 0.43; P = 0.117), and both durations were significantly longer than that in the placebo group (17.6 h, P < 0.001). Conditions for establishing non-inferiority were met.Our findings indicate that a single 10-mg intravenous dose of dexamethasone was noninferior to the combined dose of ropivacaine plus deaxmethasone in terms of duration of analgesia for foot and ankle surgery.© 2024 The Authors.