525 different drugs that can, as an adverse reaction, induce acute pancreatitis are listed in a WHO database. Compared to other causes drugs represent a relatively rare cause of pancreatitis. They should be considered as a triggering event in patients with no other identifiable cause of the disease, who takes medications that have been shown to induce pancreatitis. The prevalence of drug-induced pancreatitis is still unclear because most incidences have been documented only as isolated case reports. The overall incidence probably ranges from between 0.1 and 2% of pancreatitis cases. For only very few substances evidence from controlled trials has been obtained. Epidemiologic data suggest the risk of pancreatitis is highest for mesalazine (HR 3.5,) azathioprine (HR 2,5) and simvastatine (HR 1,8). Even when a definite association has been demonstrated it is often impossible to determine whether the drug, or the underlying condition for which the drug was taken has conferred the risk of pancreatitis (e.g. azathioprine and Crohns disease or pentamidine and HIV). Knowledge about the underlying pathophysiologic mechanisms as well as evidence for a direct causality often remains sparse. For only 31 drugs a definite causality has been established. The most frequently reported are mesalazine (nine cases in total, three cases with re-exposure), azathioprine (five cases in total, two cases with re-exposure) and simvastatin (one case in total, this one with re-exposure). As cause-effect relationship is generally accepted when symptoms re-occur upon re-challenge. Available data from case control studies suggest that even drugs with solid evidence for an association with pancreatitis only rarely cause the disease. Even when pancreatitis is induced as an adverse drug event the disease course is usually mild or even subclinical.
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