A review of the pharmacokinetic implications of schistosomiasis.

Schistosomiasis is a common parasitic disease, with over 230 million people requiring treatment annually. The worldwide increase in medication access poses risks for patients living in regions endemic for schistosomiasis because of the potential impact of pharmacokinetic changes on clinical outcomes. Thus, the objective of this review is to summarize and evaluate the published literature reporting pharmacokinetic parameters of medications in patients with schistosomiasis and to assess associated clinical implications. Thirteen articles that described the pharmacokinetics of a total of 9 different medications (cefoperazone, propranolol, praziquantel, theophylline, metronidazole, acetaminophen/paracetamol, antipyrine, oxamniquine, and oral contraceptives) in patients with schistosomiasis were included in the review. The major finding is that pharmacokinetic changes occur in patients infected with schistosomiasis but to varying degrees depending on the extent of disease (e.g., varying stages of fibrosis, with or without signs and/or symptoms of liver disease) and medication being administered. Affected patients may consequently be at risk of adverse clinical outcomes. In general, drugs with high extraction ratios demonstrate increased bioavailability in patients with schistosomiasis compared to controls. For example, propranolol and praziquantel, respectively, show an association with increased clinical and toxic effects in patients with schistosomiasis. Conversely, the pharmacokinetics of low hepatic clearance drugs (such as metronidazole and oxamniquine) are largely unchanged unless patients present with liver disease (as in the case of antipyrine, the prototypical low clearance drug). Limitations of studies included the very small numbers of patients, being primarily single-dose studies, and the high inter-individual variability. Future clinical studies should include pharmacokinetic outcomes to further clarify dosing and administration strategies for target medications, especially those that primarily undergo metabolism and are associated with significant adverse effects. Until the results of these future studies are available, clinicians should be acutely aware of complications from schistosomiasis and carefully screen patients for signs and symptoms of liver disease prior to prescribing, dispensing, or administering potentially harmful medications.