Glipizide: an oral hypoglycemic drug

Effects of CYP2C9*3 and *13 alleles on the pharmacokinetics and pharmacodynamics of glipizide in healthy Korean subjects

Glipizide is a second-generation sulfonylurea antidiabetic drug. It is principally metabolized to inactive metabolites by genetically polymorphic CYP2C9 enzyme. In this study, we investigated the effects of CYP2C9*3 and *13 variant alleles on the pharmacokinetics and pharmacodynamics of glipizide. Twenty-four healthy Korean volunteers (11 subjects with CYP2C9*1/*1, 8 subjects with CYP2C9*1/*3, and 5 subjects with CYP2C9*1/*13) were recruited for this study. They were administered a single oral dose of glipizide 5 mg. The plasma concentration of glipizide was quantified for pharmacokinetic analysis and plasma glucose and insulin concentrations were measured as pharmacodynamic parameters. The results represented that CYP2C9*3 and *13 alleles significantly affected the pharmacokinetics of glipizide. In subjects with CYP2C9*1/*3 and CYP2C9*1/*13 genotypes, the mean AUC_0-∞ were increased by 44.8% and 58.2%, respectively (both P < 0.001), compared to those of subjects with CYP2C9*1/*1 genotype, while effects of glipizide on plasma glucose and insulin levels were not significantly different between CYP2C9 genotype groups. In conclusion, individuals carrying the defective CYP2C9*3 and CYP2C9*13 alleles have markedly elevated plasma concentrations of glipizide compared with CYP2C9*1/*1 wild-type.

Metabolic-Hydroxy and Carboxy Functionalization of Alkyl Moieties in Drug Molecules: Prediction of Structure Influence and Pharmacologic Activity

Alkyl moieties-open chain or cyclic, linear, or branched-are common in drug molecules. The hydrophobicity of alkyl moieties in drug molecules is modified by metabolic hydroxy functionalization via free-radical intermediates to give primary, secondary, or tertiary alcohols depending on the class of the substrate carbon. The hydroxymethyl groups resulting from the functionalization of methyl groups are mostly oxidized further to carboxyl groups to give carboxy metabolites. As observed from the surveyed cases in this review, hydroxy functionalization leads to loss, attenuation, or retention of pharmacologic activity with respect to the parent drug. On the other hand, carboxy functionalization leads to a loss of activity with the exception of only a few cases in which activity is retained. The exceptions are those groups in which the carboxy functionalization occurs at a position distant from a well-defined primary pharmacophore. Some hydroxy metabolites, which are equiactive with their parent drugs, have been developed into ester prodrugs while carboxy metabolites, which are equiactive to their parent drugs, have been developed into drugs as per se. In this review, we present and discuss the above state of affairs for a variety of drug classes, using selected drug members to show the effect on pharmacologic activity as well as dependence of the metabolic change on drug molecular structure. The review provides a basis for informed predictions of (i) structural features required for metabolic hydroxy and carboxy functionalization of alkyl moieties in existing or planned small drug molecules, and (ii) pharmacologic activity of the metabolites resulting from hydroxy and/or carboxy functionalization of alkyl moieties.

Effect of Aqueous Extract of Azadirachta indica Leaves on Pharmacokineics and Pharmacodynamics of Glipizide

BACKGROUND

Polypharmacy, that is, two (or more) drugs administered together, may cause chemical or pharmacological interactions. Such interactions may alter the effect of either agent, leading to decrease or increase effectiveness of the drugs, which may cause adverse effects. The co-intake of complementary and alternative medicines with therapeutic medicine are supposed to influence pharmacodynamics or pharmacokinetics of the latter.

OBJECTIVE

This study was conducted to determine the interaction of glipizide (GZ) with an aqueous extract of Azadirachta indica (AZI) leaves.

METHOD

The pharmacokinetics and pharmacodynamics of glipizide was evaluated in High Fat diet (HFD) and streptozotocin induced diabetic Sprague-Dawley rats. Two doses of the AZI leaf extract (250 and 500 mg/kg) were administered alone or in combination with GZ (5 mg/kg) and serum glucose during oral glucose tolerance test, AST, ALT, and ALP levels were as estimated. In vitro CYP3A activity of AZI at 50 µg and 100 µg was assessed using liver microsomes.

RESULTS

In the glucose tolerance test, AZI and GZ showed a hypoglycemic effect. However, the hypoglycemic effect was lower when AZI was administered in combination with GZ compared with GZ alone. AZI at 100 µg has shown significant potentiation of CYP3A activity. AZI (500 mg/kg) pretreatment significantly decreased AUC and increased Tmax to 8 h.

CONCLUSION

This indicated that the pharmacokinetics and pharmacodynamics of GZ altered by AZI might be due to the induction of CYP3A activity. In conclusion, AZI can decrease the bioavailability of GZ, and hence, it should be cautiously used.

Comparative placental transport of oral hypoglycemic agents in humans: a model of human placental drug transfer

OBJECTIVE

This study compares the human placental transport of glyburide, glipizide, chlorpropamide, and tolbutamide.

STUDY DESIGN

The recirculating single cotyledon human placenta model tested maternal-to-fetal transport in term placentas perfused immediately after delivery. Drug levels were measured by high-performance liquid chromatography and liquid scintillation spectrometry, and transport rates were calculated by comparing maternal and fetal concentrations.

RESULTS

The transport of these substances differed significantly over a tenfold range (analysis of variance, p < 0.0008). A significant association exists by multiple linear regression between drug transfer and molecular weight, dissociation constant, and the octanol-water partition coefficient (R2 = 0.91, p < 0.0001).

CONCLUSIONS

There is significant variability in human placental transfer rates of the oral hypoglycemics, which strongly correlates with molecular properties. These data suggest that less fetal exposure may occur with second-generation sulfonylureas and anticipate that regression models may be useful in selecting agents that minimize placental transport to the fetus.