3 The pharmacology of the cytochrome P450 enzyme system

Genotoxic and biochemical effects of atrazine and Roundup(®), alone and in combination, on the Asian clam Corbicula fluminea

The present study aimed to evaluate biochemical and genotoxic effects of the herbicides atrazine (ATZ) and Roundup(®) (RD) separately, as well as their mixture, on the freshwater clam Corbicula fluminea after 96 h exposure. Animals were exposed to 2 and 10 ppb of ATZ (ATZ2 and ATZ10), 2 and 10 ppm of RD (RD2 and RD10) and the following mixtures: 2 ppb ATZ+2ppm RD (AR2) and 10 ppb ATZ+10 ppm RD (AR10). Activities of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR), as well as the multixenobiotic resistance mechanism (MXR), reduced glutathione concentrations (GSH) and lipid peroxidation (LPO) were measured in gills and digestive gland. DNA damage was determined in clams hemocytes through the comet assay. The gills were more susceptible to the action of the herbicides and the results showed that ATZ2 and ATZ10 caused a significant reduction in EROD and the mixture leads to a significant decrease in EROD and MXR. No significant change in the biotransformation parameters was observed in the digestive gland. Regarding the primary antioxidant defenses, SOD activity increased in the gills of clams exposed to ATZ10 and RD10 and in the digestive gland of animals exposed to RD2 and RD10, CAT activity was significantly reduced only in digestive gland of clams exposed RD10 while GPX increased in the gills after exposure to ATZ2 and RD10. The exposure to RD10 caused a significant increase in LPO in both gills and digestive gland. While the exposure to ATZ and RD separately did not increase DNA damage, the exposure to AR2 and AR10 caused a significant increase in the occurrence of DNA damage. In conclusion, this study showed that both herbicides applied alone caused effects on C. fluminea; ATZ interfered mostly in biotransformation while RD interfered mainly in antioxidant defenses leading to lipid peroxidation. The herbicides mixture showed antagonistic effects on the gills EROD and on lipid peroxidation in gills and digestive gland and synergistic effects on the gills MXR and on DNA damage in the hemocytes.

[Clinically relevant pharmacokinetic drug interactions in the intensive care unit: an overview]

Critically ill patients in the intensive care unit (ICU) are predisposed to pharmacokinetic drug interactions because of the complexity of the drug regimens received in the intensive care setting. Drugs may affect the absorption, distribution, metabolism and/or elimination of an object drug and consequently alter the intended pharmacologic response and potentially lead to an adverse event. The paper presents an overview of pharmacokinetic drug-drug interactions which can occur with commonly used drugs in the ICU and outlines the underlying types and mechanisms.

[Drug interactions and the anesthesiologist]

Modern anesthesiology employs the combined administration of several drugs belonging to different pharmacological classes. Additionally, anesthesiologists are facing the challenge of polypharmacy regimens utilized by patients considered for surgical treatment When drugs are combined, the pharmacological effect may considerably differ from the individually expected properties. This may be beneficial or potentially lead to adverse drug reactions harming the patient. The incidence of drug interaction increases exponentially with the number of drugs administered. Depending on the mechanism involved, drug interactions can be classified as pharmaceutical, pharmacodynamic, or pharmacokinetic. Although there are enormous possibilities for adverse drug reactions nd the complexity is hard to identify, prediction of drug interaction is possible. Besides recognizing the general risk factors, fundamental knowledge of basic and clinical pharmacology is important to prevent serious or fatal drug interactions before they occur.