Pharmacokinetic profiles of metamizole (dipyrone) active metabolites in goats and its residues in milk.

Metamizole (dipyrone, MET) is a nonopioid analgesic drug commonly used in human and veterinary medicine. The aim of this study was to assess two major active metabolites of MET, 4-methylaminoantipyrin (MAA) and 4-aminoantipyrin (AA), in goat plasma after intravenous (IV) and intramuscular (IM) administration. In addition, metabolite concentration in milk was monitored after IM injection. Six healthy female goats received MET at a dose of 25 mg/kg by IV and IM routes in a crossover design study. The blood and milk samples were analyzed using HPLC coupled with ultraviolet detector and the plasma vs concentration curves analyzed by a noncompartmental model. In the goat, the MET rapidly converted into MAA and the mean maximum concentration was 183.97 µg/ml (at 0.08 hr) and 51.94 µg/ml (at 0.70 hr) after IV and IM administration, respectively. The area under the curve and mean residual time values were higher in the IM than the IV administered goats. The average concentration of AA was lower than MAA in both groups. Over 1 µg/ml of MAA was found in the milk (at 48 hr) after MET IM administration. In conclusion, IM is considered to be a better administration route in terms of its complete absorption with long persistence in the plasma. However, this therapeutic option should be considered in light of the likelihood of there being milk residue.

Optimization of dispersive liquid-liquid microextraction for preconcentration and spectrophotometric determination of phenols in Chabahar Bay seawater after derivatization with 4-aminoantipyrine.

We have optimized dispersive liquid-liquid microextraction to preconcentrate trace phenolic compounds after derivatization with 4-aminoantipyrine in artificial sea water for spectrophotometric determination. Factors such as reaction time (7.5 min), pH (9.5), solvent (chloroform), dispersing solvent (ethanol), and volume ratio of dispersing to organic phase (11:1) were optimized. Under optimum conditions, the limit of detection was 0.18 µg/L and the linearity range 1-900 µg/L. The relative standard deviation and enrichment factor were 6% (n=7) and 920, respectively. The results demonstrate the efficiency of coupling the 5530 APHA standard for derivation and dispersive liquid-liquid microextraction of phenolic compounds from seawater samples. Using this method, total phenol content in seawater from several locations in Chabahar Bay (southeast Iran) was estimated at 27.8-74.8 µg/L.

Graphene matrix for signal enhancement in ambient plasma assisted laser desorption ionization mass spectrometry.

In this work, the signal intensity of ambient plasma assisted laser desorption ionization mass spectrometry (PALDI-MS) was significantly increased with graphene as matrix. The graphene functions as a substrate to trap analytes, absorb energy from the visible laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. The desorbed analytes are further ionized by helium plasma and analyzed by MS. Compared with a traditional organic matrix, α-cyano-4-hydroxycinnamic acid (CHCA), graphene exhibited much higher desorption efficiency for most of the compounds benefitting from the strong optical absorption at 532nm. The performance has been confirmed by the facile analysis of more than forty compounds with various structures. Additionally, this method was successfully applied to distinguish three kinds of Chinese tea leaves by detecting the endogenous caffeine and theanine, which proved the utility, facility and convenience of this method for rapid screening of main components in real samples.

Validation of a new high-performance liquid chromatography assay for nizatidine.

An expedient high-performance liquid chromatography (HPLC) assay for nizatidine measurement in human plasma was developed and validated. After deproteinization of 200 microL of plasma by filtration, nizatidine and 4-amino-antipyrine (internal standard) were separated (capacity ratio 3.0 and 6.63, respectively) on Nova-Pak C18 cartridge at room temperature (RT), and detected spectrophotometrically at 320 nm. The mobile phase, 0.02 mol/L disodium hydrogen phosphate, acetonitrile, methanol, and triethylamine (80:10:10:0.05 vol/vol), was delivered at 1.5 mL/min. Calibration curves were linear (r2 > or = 0.999) in the range 0.02 to 5 microg/mL, detection and quantification limits were 0.01 and 0.02 microg/mL, respectively, intra-run and inter-run coefficients of variation were < or = 3.5% and < or = 4.2%, respectively, and recovery was >90%. Nizatidine was stable for at least 4 hours at RT, 12 weeks at -20 degrees C, and 3 freeze-thaw cycles in plasma; 16 hours at RT and 48 hours at -20 degrees C in deproteinized plasma; and 6 hours at RT and 3 weeks at -20 degrees C in water.

Spectrophotometric determination of ritodrine and isoxsuprine hydrochlorides using 4-aminoantipyrine.

A simple, accurate, and rapid method for the quantitative determination of ritodrine hydrochloride (RTH) and isoxsuprine hydrochloride (ISH) in both pure and dosage forms, is described. The method is based on the development of pink colored product as a result of the condensation of 4-aminoantipyrine with phenols in the presence of an alkaline oxidizing agent. The resulting products are measured at 510 nm for both drugs, with molar absorptivities of 0.98 x 10(4) and 1.20 x 10(4) L/mol x cm for RTH and ISH, respectively. A study of the effect of commonly associated excipients revealed that they did not cause interference.

Evaluation and comparison of colorimetric, radiometric and high performance liquid chromatographic assays for aminopyrine-N-demethylation by rat liver microsomes.

Aminopyrine (DMAP) is metabolized by two successive N-demethylations to monomethyl-4-aminoantipyrine (MMAP) and 4-aminoantipyrine (AAP). Separation and quantification of DMAP and its metabolites in microsomal incubation mixtures by h.p.l.c. showed that other reactions also occur. In the radiometric method where [Me2-14C]DMAP is used as substrate, [14C]formaldehyde is formed during the N-demethylation. However since commercial [14C]DMAP, is not completely double labelled, and both MMAP and AAP are formed, it is impossible to calculate the formaldehyde formation accurately from the specific activity of [14C]DMAP. Moreover, it was shown that DMAP, AAP and particularly MMAP may all develop considerable colour intensity with the Nash reagent, which is used to determine formaldehyde. Despite this difficulty, DMAP may still be used as a model substrate in vitro, with the Nash assay being used to determine formaldehyde if low substrate concentrations and a short incubation time are used. Thus the interference of DMAP or its metabolites with the Nash assay is negligible. As the same Km and Vmax values were obtained from both the radiometric and the relatively precise colorimetric assay it is suggested that there is little wrong with either method, at least under our experimental conditions. The h.p.l.c. method however, underestimates formaldehyde formation, probably because metabolites other than MMAP and AAP are formed. The latter method however may be used to analyse the aminopyrine metabolism in more detail.

Radioimmunoassay for pyrazolone derivatives.

The determination of pyrazolone derivatives by radioimmunoassay has been reported. Anti-antipyrine antisera were obtained by repeated immunization of rabbits with 4-azoantipyrine-conjugated bovine serum albumin. The level at least as low as 1.0 ng of antipyrine could be detected by this procedure. Various substituents on the carbon 4 position of the pyrazolone ring as well as the lack of methyl group on the nitrogen 2 position decreased the affinity for the antibody, and the antibody showed no cross-reaction with any pyrazolidine derivatives.