Propofol is commonly used in anesthesia practice according to its rapid and smooth induction, short duration, and low incidence of postoperative nausea and vomiting. However, discomfort from pain on propofol injection still be a problem.1-4 The incidence of this pain in adults ranged from 28 to 90% and its pain severity was moderate (average numeric rating scale (NRS) was 5.6±2.3).5-7 The mechanism of propofol injection pain was hypothesized that propofol likely irritates the innermost layer of vessels that causes directly stimulating free nerve ending and indirectly releasing of mediators and results in pain on injection.6-8 Several methods were used for alleviating propofol injection pain such as pretreatment of intravenous lidocaine with or without tourniquet, lidocaine mixed with propofol, and pretreatment with opioids, non-steroidal anti-inflammatory drugs, ketamine, or metoclopramide.6-9 Pre-treatment of lidocaine is a common technique to prevent propofol pain because of its local anesthetic effect on the vein and ease to application.7-9 Pretreatment of 30 to 60 mg of intravenous lidocaine with tourniquet was presumed to reduce this pain.9-11 However, appropriate dosages and methods of lidocaine administration were inconclusive and the efficacy of lidocaine administration on propofol injection pain was still varied. From earlier study, 20 mg of Hyoscine N-butylbromide (HBB) significantly alleviated propofol pain on injection when compared to placebo.12 HBB, a quaternary ammonium derivative which an anticholinergic drug, bound to peripheral anti-muscarinic receptors which are located notably in smooth muscle cells of gastrointestinal tract and blood vessels.13,14 It is used for relief abdominal, ureteric colic, labor pain, and prevent spasms of the gastrointestinal tract prior to invasive radiologic and diagnostic procedures, such as endoscopic retrograde cholangiopancreatography (ERCP) and colonoscopy.13-16 Common adverse effects of HBB were tachycardia, dry mouth, and blurred vision.14 This study was intended to compare the efficacy between pretreatment of HBB and lidocaine in adjunction with tourniquet to alleviate propofol pain on injection.