Highly sensitive and specific gas chromatographic-tandem mass spectrometric method for the determination of trace amounts of antipyrine metabolites in biological material

New spectral resolution techniques for resolving and determining the components in binary fixed-dose combinations

Four spectrophotometric approaches were performed to determine a binary combination of Phenazone and Benzocaine in pure powder form and in pharmaceutical formations. This investigation submits the application of four techniques contingent on the presence of the extended area of the spectra of one compound in the binary mixture, these methods include Absorptivity Centering (a-centering), Absorbance Subtraction (AS), Amplitude Modulation (AM) and Concentration Value (CV). The linearity range for the above-mentioned approaches was found to be 3.0-15.0 μg/mL for Benzocaine in a-centering method and 3.0-30.0 μg/mL for Benzocaine and Phenazone in other advanced methods. The four techniques were evaluated as per ICH criteria and were successfully utilized for the determination of Phenazone and Benzocaine existing in pharmaceutical formulations. All results gained by the submitted approaches were statistically compared with a previously published method, and no important differences were detected.

Titanium nanoparticles (TiO2)/graphene oxide nanosheets (GO): an electrochemical sensing platform for the sensitive and simultaneous determination of benzocaine in the presence of antipyrine

An effective electrochemical sensing platform for the simultaneous determination of benzocaine (BEN) and antipyrine (ANT).

Antipyrine as a probe for human oxidative drug metabolism: identification of the cytochrome P450 enzymes catalyzing 4-hydroxyantipyrine, 3-hydroxymethylantipyrine, and norantipyrine formation

BACKGROUND AND OBJECTIVE

Antipyrine has been widely used as a probe drug for human oxidative drug metabolism. To evaluate the role of antipyrine as a model drug, we have identified the cytochrome P450 enzymes involved in 4-hydroxyantipyrine, 3-hydroxymethylantipyrine, and norantipyrine formation.

METHODS

We used the following methods for this study: (1) determination of enzyme kinetics for antipyrine metabolite formation in human liver microsomes, (2) inhibition studies with antibodies and inhibitors, and (3) formation of metabolites by stable expressed human P450 enzymes.

RESULTS

Antipyrine biotransformation could be described by Michaelis-Menten kinetics: norantipyrine: maximum rate of metabolite formation (Vmax), 0.91 +/- 0.04 nmol . mg-1 . min-1; Michaelis-Menten constant (Km), 19.0 +/- 0.8 mmol/L; 4-hydroxyantipyrine: Vmax, 1.54 +/- 0.08 nmol . mg-1 . min-1;Km,39.6 +/- 2.5 mmol/L. Antibodies against CYP3A4 inhibited the formation of 4-hydroxyantipyrine by 25% to 65%. LKM-2 antibodies (anti-CYP2C) caused a 75% to 100% inhibition of norantipyrine and a 58% to 80% inhibition of 3-hydroxymethylantipyrine formation. Sulfaphenazole inhibited the formation of 3-hydroxymethylantipyrine and norantipyrine by about 50%. Furafylline and fluvoxamine inhibited norantipyrine, 4-hydroxyantipyrine, and 3-hydroxymethylantipyrine formation by about 30%, 30%, and 50%, respectively. Ketoconazole reduced formation of norantipyrine, 3-hydroxymethylantipyrine, and 4-hydroxyantipyrine by up to 80%. Formation in stable expressed enzymes indicated involvement of CYP1A2, CYP2B6, CYP2C, and CYP3A4 in metabolite formation.

CONCLUSION

Antipyrine metabolites are formed by at least six hepatic cytochrome P450 enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C18, and CYP3A4). 4-Hydroxylation is mainly catalyzed by CYP3A4 and, to a lesser extent, by CYP1A2. The CYP2C subfamily contains the predominant enzymes for norantipyrine formation, and CYP1A2 is also involved. Formation of 3-hydroxymethylantipyrine is mediated by CYP1A2 and CYP2C9. Because several cytochrome P450 enzymes are involved in the formation of each metabolite, antipyrine is not well suited as a probe for distinct human cytochrome P450 enzymes.