Synergistic electrocatalytic activity of In2O3@FMWCNTs nanocomposite for electrochemical quantification of dobutamine in clinical patient blood and in injection dosage form.

Dobutamine (DBT) is a sympathomimetic amine drug that was designed as an inotropic agent for use in congestive heart failure. Hence, there was an impetus to develop a rapid and accurate method for monitoring the concentration of DBT within clinical samples. To address this critical need, a novel In2O3 and functionalized multi-walled carbon nanotubes nanocomposite (In2O3@FMWCNTs) was successfully prepared and applied in an electrochemical sensor to detect DBT. The resulting sensor displayed electrocatalytic toward the oxidation of DBT, which attributed to the synergistic effect of In2O3 and FMWCNTs. Electrochemical impedance spectroscopy (EIS) studies revealed that the smaller charge transfer resistance value (Rct) was observed at In2O3@FMWCNTs modified glassy carbon spherical (GCS) paste electrode (PE) as compared to that of In2O3NPs/GCSPE, FMWCNTs/GCSPE and GCSPE, which authenticates its good conductivity. Furthermore, the calculated value of standard rate constant (ks) for the modified electrode demonstrates the fast electron transfer between DBT and the electrode surface. The fabricated electrochemical sensor indicated high selectivity and sensitivity for DBT determination over the oxidation of uric acid and ascorbic acid. The limit of detection of DBT at In2O3@FMWCNTs/GCSPE was found to be 1.42 × 10-10 M. The proposed sensor is effectively used for the detection of DBT in biological fluids, clinical patient blood and in injection dosage form.

Coupling reaction and complex formation for the spectrophotometric determination of physiologically active catecholamines in bulk, pharmaceutical preparations and urine samples of schizophrenic patients.

A simple and sensitive spectrophotometric method for the determination of three catecholamines namely dopamine hydrochloride (DO.HCl), dobutamine hydrochloride (DOB.HCl) and vanillymandelic acid (VMA), in both pure form or in their commercially available pharmaceutical formulations or urine samples of schizopherinic patients is described. The method is based on the reaction of diazotized 4-aminoantipyrine (4-AAP) with catecholamines in a basic medium (pH = 10-11) to yield pink-coloured products having absorption maxima at 500, 505 and 480 nm for DO.HCl, VMA and DOB.HCl, respectively. Before carrying out Beer's Law, different experimental conditions, such as time, temperature, sequence of addition, and pH are optimized. The coloured species obeyed Beer's Law in the range of 47.4-417.2, 59.45-445.9 and 67.57-405.4 mg/L for DO.HCl, VMA and DOB.HCl, respectively. The molar absorptivity values as obtained from Beer's Law data were found to be 2.979 x 10(4), 4.39 x 10(4) and 1.036 x 10(4) L mol(-1) cm(-1), while Sandell's sensitivity values were observed to be 3 x 10(-3), 4.4 x 10(-3) and 1.3 x 10(-3) microg cm(2-) for DO.HCl, VMA and DOB.HCl, respectively. Common excipients did not interfere with the proposed method. The results of the proposed method compare favourably with those of official methods. The proposed method offers simplicity, reliability, rapidity, and accuracy compared to the existing methods.

Comparison of electrospray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization in the identification of apomorphine, dobutamine, and entacapone phase II metabolites in biological samples.

The applicability of different ionization techniques, electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and a novel atmospheric pressure photoionization (APPI), were tested for the identification of the phase II metabolites of apomorphine, dobutamine, and entacapone in rat urine and in vitro incubation mixtures (rat hepatocytes and human liver microsomes). ESI proved to be the most suitable ionization method; it enabled detection of 22 conjugates, whereas APCI and APPI showed only 12 and 14 conjugates, respectively. Methyl conjugates were detected with all ionization methods. Glucuronide conjugates were ionized most efficiently with ESI. Only some of the glucuronides detected with ESI were detected with APCI and APPI. Sulfate conjugates were detected only with ESI. MS/MS experiments showed that the site of glucuronidation or sulfation could not be determined, since the primary cleavage was a loss of the conjugate group (glucuronic acid or SO3), and no site-characteristic product ions were formed. However, it may be possible to determine the site of methylation, since methylated products are more stable than glucuronides or sulfates. Furthermore, the loss of CH3 is not necessarily the primary cleavage, and site characteristic products may be formed. Identification and comparison of conjugates formed from the current model drugs were successfully analyzed in different biological specimens of common interest to biomedical research. A fairly good relation was obtained between the data from in vivo and in vitro models of drug metabolism.

3-O-methyldobutamine, a major metabolite of dobutamine in humans.

Dobutamine is a synthetic ionotropic catecholamine commonly used to treat heart failure and shock. The catabolic fate of dobutamine in humans has yet to be reported, although formation of 3-O-methyldobutamine represents the principal pathway of dobutamine disposition in the dog. Herein, we describe the isolation and identification of 3-O-methyldobutamine in the urine of children receiving infusions of racemic dobutamine. In a 9-year-old child with heart failure approximately 80% of dobutamine administered intravenously at steady state was detected in the urine. Forty-seven percent of infused dobutamine was identified as 3-O-methyldobutamine and its acid-hydrolyzed derivatives, the latter mostly conjugated with sulfate (33%). Thirty-two percent consisted of acid-hydrolyzed dobutamine metabolites, primarily conjugated with sulfate (16%). Sonicates of human blood mononuclear cells catalyzed the formation of 3-O-methyldobutamine from dobutamine and S-adenosylmethionine in vitro. These findings indicate that formation of 3-O-methyldobutamine constitutes a major pathway of dobutamine metabolism in humans.

Sulfoconjugation and renal excretion contribute to the interpatient variation of exogenous catecholamine clearance in critically ill children.

OBJECTIVE: To delineate the contributions of sulfoconjugation, renal excretion, and patient age to the wide interpatient variability in exogenous dobutamine and dopamine plasma clearance. DESIGN: Simultaneous plasma free and sulfoconjugated dobutamine and/or dopamine, respective urine free catecholamine, and serum creatinine were determined on stable critically ill children receiving unchanged continuous infusions of dobutamine and/or dopamine for at least 1 hr. Free dobutamine and dopamine clearance rates were calculated. SETTING: Pediatric and neonatal intensive care units in university settings. PATIENTS: Forty-seven stable critically ill neonates and children. INTERVENTIONS: Continuous infusions of dobutamine and/or dopamine: nine patients received dopamine only, 27 patients received dobutamine only, and 11 patients received both simultaneously. MEASUREMENTS AND MAIN RESULTS: Fractions of plasma dobutamine and dopamine sulfoconjugated were 0.73 +/- 0.05 and 0.76 +/- 0.05, respectively. Free plasma dobutamine and dopamine clearances were 102 +/- 15 mL/kg/min and 250 +/- 38 mL/kg/min, respectively. Linear regression analyses demonstrated relationships of the fraction of plasma dobutamine and dopamine sulfoconjugated to the respective free plasma clearances (r2 = .30, p < .01, and r2 = 0.29, p < .01, respectively), and, more impressively, to the natural logarithm of the respective free plasma clearances (r2 = 0.58, p < .001, and r2 = 0.39, p < .01). Patients with serum creatinine concentrations >2 mg/dL had lower free plasma dobutamine and dopamine clearance rates than those patients with serum creatinine of <2 mg/dL (6 +/- 1 vs. 107 +/- 15 mL/kg/min for dobutamine and 40 +/- 38 vs. 270 +/- 39 mL/kg/min for dopamine, respectively, p < .05 for both by Mann-Whitney U test). No relationship was noted between free catecholamine clearance and age. CONCLUSION: Sulfoconjugation and renal excretion are important determinants of the wide interpatient variability in plasma free dobutamine and dopamine clearance rates.

Simultaneous determination of catecholamines and dobutamine in human plasma and urine by high-performance liquid chromatography with fluorimetric detection.

We report a reliable fluorimetric assay for the simultaneous determination of norepinephrine, epinephrine, dopamine and dobutamine in human plasma and urine, based on liquid-liquid extraction and derivatization with the fluorogenic agent 1,2-diphenylethylenediamine prior to chromatography. The method is sensitive (detection limit 0.3-0.8 pg injected) and reproducible (coefficients of variation 1-10%), and shows good accuracy (93-98%). The method should also be used when one only wants to measure the concentrations of the natural catecholamines, in order to avoid interference by metabolites of dobutamine and by the late-eluting dobutamine itself.