Hepatobiliary scans using Tc-IDA are reliable in making the diagnosis of acute cholecystitis. Commonly, opioid drugs are administered in patients with acute cholecystitis to relieve pain. Opioid drugs cause biliary sphincter spasm. Whether these drugs adversely affect hepatobiliary scans is unknown. We studied 13 healthy volunteer subjects, performing three hepatobiliary scans in each one. Scans were performed without opioid drugs and 30 minutes after intramuscularly administered meperidine, morphine, hydroxyzine, hydroxyzine plus meperidine, butorphanol, and nalbuphine. Opioid drugs markedly delayed clearance of Tc-IDA from the common bile duct, simulating common bile duct obstruction. Hydroxyzine alone caused an insignificant delay. We have concluded that opioid drugs cause bile duct obstruction in healthy persons. If opioid drugs are administered before a diagnostic hepatobiliary scan, delayed clearance of Tc-IDA from the common bile duct might lead to an erroneous diagnosis and indicate a potentially unnecessary common bile duct exploration. Opioid drugs should not be administered for several hours before a diagnostic hepatobiliary scan.