Prolonged use of opiate agonists commonly results in constipation, particularly with codeine, meperidine, methadone, and morphine however meperidine appears to cause less constipation than the others. Hyperamylasemia, secondary to drug-induced spasm of the sphincter of Oddi, has been associated with various opiate agonists. While serum amylase and lipase concentrations can rise as a result of biliary obstruction or spasm, overt pancreatitis is rare with opiate analgesics. Gastritis and hepatotoxicity are also relatively rare with these agents. Diaphoresis and flushing may be associated with hydrocodone, meperidine, methadone, or morphine.
Opiate agonists can cause cardiovascular adverse reactions.
These reactions include sinus bradycardia, sinus tachycardia, palpitations, hypertension, hypotension, orthostatic hypotension, and syncope. Anticholinergic effects occur with meperidine but are infrequent. Opiate agonists present the potential for abuse although the true risk of this phenomenon is extremely low. Patients with chronic pain may be inclined to misuse these drugs. Mild physiological dependence, however, can occur commonly during therapy with opiate agonists and abrupt discontinuation of the drug in these patients can provoke a withdrawal syndrome.