The absorption of oral drug in the intestine is an important factor to determine the drug bioavailability. There are many intestinal transporters mediating drug absorption, distribution, excretion and drug-drug interaction. Understanding the transport mechanism can improve the effectiveness and safety of drug and guide clinical rational use of drugs. The in vivo and in vitro methods are used to predict the transport mechanism of drugs by intestinal transporters in the intestine. The purposes of this article are to introduce the main transporters in the intestinal tract, to explain the transport mechanism and to summarize the advantages and disadvantages of the research methods of them.

With the wide application of Chinese herbal medicine, herb-drug interaction (HDI) has become increasingly prominent. Metabolic enzymes and transporters are the main targets of HDI, because the changes in expression and function of enzymes and transporters can influence the disposition of drugs. Metabolic enzymes are responsible for the metabolic clearance of drugs, including cytochrome P450 (CYP), UDP-glucuronyl transferase (UGT) and sulfotransferases (SULT); transporters widely expressed in the intestine, kidney, liver and brain are involved in the oral absorption, distribution and excretion of drugs. Pueraria, ginkgo, ginseng, St. John's wort and other Chinese herbal medicine often induce a HDI because those herbal medicines combined with chemical medicine are widely used in clinic. The components of herb medicines mentioned above are prone to interact with enzymes and transporters, which often induce a HDI. This paper reviews the advances in the study of enzymes and transporters-mediated pharmacokinetic mechanism of HDI.

Drug-drug interaction (DDI) is referred as the changes of physical and chemical properties, as well as the pharmacokinetics or pharmacodynamics of drugs administered simultaneously or consecutively. The clinical results for drug-drug interaction could be divided into good clinical efficacy and adverse interaction. With the kinds of drugs increasing every year, new drug resistances spring up frequently. This phenomenon makes drug combination increased so that the drug interaction, especially the adverse interaction emerged. The mechanisms of in vivo drug-drug interaction are relevant to a number of factors, including drug-metabolizing enzyme systems and membrane transporters. Recent studies have revealed the important role played by transporters in drug absorption, distribution, metabolism and elimination. In order to avoid severe side effects mediated by transporters and to promote rational combination in clinics, the mechanisms of intestinal absorption and renal excretion mediated by transporters are reviewed.

Multidrug regimens and corresponding drug interactions cause many adverse reactions and treatment failures. Drug efflux transporters: P-glycoprotein (P-gp), multidrug resistance associated protein (MRP) and breast cancer resistance protein (BCRP) in conjunction with metabolizing enzymes (cytochrome P450, CYP450) are major factors in such interaction. In recent years, a large number of studies have shown that P-gp plays a role in the oxidative metabolism of its substrates that are also substrates of CYP3A4. Combined actions of P-gp and CYP3A could account in some part for the low oral bioavailability determined for many of these dual substrates. P-gp along with efflux transporters (MRP and BCRP) having overlapping substrate specificity plays critical role in drug disposition. The relationship between MRP or BCRP and CYP3A is similar to that between P-gp and CYP3A. In this paper, we summarize the classification of efflux transporters, the main metabolizing enzymes CYP3A, clinical significance interactions mediated by efflux transporters and CYP450 enzymes and in vitro studies.

Drug transporters are functional membrane proteins located in various tissues, which play vital roles in absorption, distribution and excretion of drugs, especially those located in intestine, liver and kidney. The expression and function of transporters will alter in diseases state, which affects the therapeutic effects of drugs by altering their pharmacokinetics. In this review, we focus on the alterations in related transporters and the effect on the drug therapy in common intestinal diseases, liver diseases, kidney diseases and diabetes mellitus.

Metformin is the most commonly prescibed drug for type 2 diabetes mellitus as it is inexpensive, safe, and efficient in ameliorating hyperglycemia and hyperinsulinemia. Numerous epidemiological studies indicate that diabetic population is not only at increased risk of cardiovascular complications, but also at substantially higher risk of many forms of malignancies. Meanwhile, epidemiological and clinical observation studies have shown that metformin use reduces risk of cancer in patients with type 2 diabetes mellitus and improves prognosis and survival rate of the cancer patients. Furthermore, metformin has been used for cancer therapy in clinical trials. Thus, metformin is emerging as a new cancer therapy or adjuvant anticancer drugs. This review summarizes recent progress in studies of metformin use and its molecular mechanism.

H+/oligopeptide cotransporter PEPT1 mainly located at the brush border membrane of intestinal epithelium cell. transports dipeptide/tripeptide which is the degradation products of protein in digestive tract. Peptide-like drugs such as ?-lactam antibiotics,angiotensin-converting enzyme inhibitor (ACEI) and non-peptide drugs valaciclovir also can be transported and uptaked by PEPT1. PEPT1 is important for maintaining the homeostasis and the absorption of drugs in gastrointestinal tract. With the further research of PEPT1 gene, protein structure, and functional activity, we have known the factors about regulation of PEPT1 expression in membrane, their functional activities and substrate affinities. Some associated mechanism of regulation have been studied. As the wide substrate specificities of PEPT1, it becomes the target molecular on drug development and implication for drug delivery. Studies about interactions of PEPT1 with drugs are important for knowing the interactions of drugs, evaluating bioavailability of drug by intestinal absorption, researching the target treatment in anti-tumor drugs and individualization administration.

OBJECTIVE:To explore the effect of clinical pharmacist intervention on the rational use of Alanyl-glutamine injection.METHODS:Referring to package inserts of Alanyl-glutamine injection,Clinical Pharmacy Consensus of Parenteral Nutrition,ASPEN Nutrition Therapy Guidelines for Critically Ill Patients,related domestic and foreign literatures,evaluation criteria for Alanyl-glutamine injection rational use was formulated.After collecting Alanyl-glutamine injection cases (497 cases) in the second quarter of 2015 and those cases (385 cases) in the second quarter of 2016,rational use of Alanyl-glutamine injection were analyzed comparatively before and after intervention.RESULTS:The utilization rate and irrational rate of Alanyl-glutamine injection were 4.6％ and 52.9％ before intervention as well as 2.9％ and 10.9％ after intervention,with statistical significance (P＜0.05).There was statistical significance in hyper-indication,excessive concentration of drug liquid,excessive supply of amino acid,irrational compatibility and solvent selection,long treatment course before and after intervention (P＜0.05).CONCLUSIONS:Clinical pharmacists reduce irrational rate of drug use and guarantee safe and effective drug use through formulating evaluation criteria for Alanyl-glutamine injection rational use and providing pharmaceutical intervention on rational use of Alanyl-glutamine injection.

0.05).The bioequivalence of test tablets was (105.7?13.9)%.CONCLUSION:The results of statistics analysis show that the test and reference tablets were bioequivalent.

Objective To analyze the clinical characteristics,diagnosis,differential diagnosis and treatment of gastrointestinal schwannoma.Methods Clinical data of 3 patients with gastrointestinal schwannoma were collected and retrospectively analyzed.Results Gastrointestinal bleeding or melena,anemia and epigastric pain were the most common presenting symptoms.The symptoms,physical signs and auxitiary examinations (such as X-ray,ultrasonography and gastrointestinal endoscopy) of gastrointestinal schwannoma had no value in differentiation.In all the 3 patients definite diagnosis was achieved only by postoperative pathology.Conclusion Gastrointestinal schwannoma are derived from the Schwann cells of nerves in gastrointestinal wall and are usually benign.Benign schwannomas can only be distinguished from the malignant ones on the basis of histological and immunohistochemical criteria.Surgical resection is the most effective treatment.