Subhash C. Jamdar

Determination of cocaine, norcocaine, benzoylecgonine and ecgonine methyl ester in rat plasma by high-performance liquid chromatography with ultraviolet detection

An isocratic high-performance liquid chromatographic method with ultraviolet detection at 235 nm is described for the determination of cocaine and its metabolites benzoylecgonine, norcocaine and ecgonine methyl ester in rat plasma, collected during toxicity studies. Following simultaneous solid-phase extraction of all analytes and the internal standard tropacocaine, cocaine, benzoylecgonine and norcocaine were separated on a C18 column. Ecgonine methyl ester and cocaine were separated on coupled cyanopropyl and silica columns, following derivatization of ecgonine methyl ester to p-fluorococaine. The extraction efficiencies of these compounds from plasma ranged from 78 to 87%, while the limits of detection ranged from 35 to 90 ng/ml. The assay was linear from 300 to 5000 ng/ml, and the within-day precision 2 to 8% over this concentration range.

Consequences of Electroencephalographic-suppressive Doses of Propofol in Conjunction with Deep Hypothermic Circulatory Arrest

Background Some patients who undergo cerebral aneurysm surgery require cardiopulmonary bypass and deep hypothermic circulatory arrest. During bypass, these patients often are given large doses of a supplemental anesthetic agent in the hope that additional cerebral protection will be provided. Pharmacologic brain protection, however, has been associated with undesirable side effects. These side effects were evaluated in patients who received large doses of propofol. Methods Thirteen neurosurgical patients underwent cardiopulmonary bypass and deep hypothermic circulatory arrest to facilitate clip application to a giant or otherwise high-risk cerebral aneurysm. Electroencephalographic burst suppression was established before bypass with an infusion of propofol, and the infusion was continued until the end of surgery. Hemodynamic and echocardiographic measurements were made before and during the prebypass propofol infusion and again after bypass. Emergence time also was determined. Results Prebypass propofol at 243 plus/minus 57 micro gram *symbol* kg sup -1 *symbol* min sup -1 decreased vascular resistance from 34 plus/minus 8 to 27 plus/minus 8 units without changing heart rate, arterial or filling pressures, cardiac index, stroke volume, or ejection fraction. Propofol blood concentration was 8 plus/minus 2 micro gram/ml. Myocardial wall motion appeared hyperdynamic at the end of cardiopulmonary bypass, and all patients were weaned therefrom without inotropic support. After bypass, vascular resistance decreased further, and cardiovascular performance was improved compared to baseline values. Nine of the 13 patients emerged from anesthesia and were able to follow commands at 3.1 plus/minus 1.4 h. Three others had strokes and a fourth had cerebral swelling. Conclusions Propofol infused at a rate sufficient to suppress the electroencephalogram does not depress the heart or excessively prolong emergence from anesthesia after cardiopulmonary bypass and deep hypothermic circulatory arrest.

Cocaine, norcocaine, ecgonine methylester and benzoylecgonine pharmacokinetics in the rat

Abstract We have compared the pharmacokinetics of bolus dose cocaine administration with that of its three most important metabolites; norcocaine, ecgonine methylester, and benzoylecgonine and assessed whether kinetics are dose dependent at two equimolar doses equivalent to cocaine hydrochloride 2.5 and 5 mg kg respectively. Forty-nine male Sprague-Dawley rats were randomly divided into 8 groups to receive iv either high (14.7 umol kg ) (HI) or low (7.3 umol kg ) (LO) bolus doses of cocaine or one of its metabolites. Arterial blood samples for cocaine and metabolite analysis were taken repetitively over the next 3 h. Equimolar bolus doses of these congeners showed biexponential plasma concentration decay curves which were fitted to a two compartment model and subjected to noncompartmental analysis. The plasma concentration time profiles were significantly different for the HI and LO doses administered for each congener. The elimination half-lives of cocaine and norcocaine were similar (28–33 min), that for ecgonine methylester (60–71 min) was approximately twice this and for benzoylecgonine was 40–44 min. Cocaine clearance (155–158 ml/kg/min) was found to be in the range found in other rat studies. Ecgonine methylester clearance and benzoylecgonine clearance were found to be one quarter and one eighth of this value respectively. The pharmacokinetic profile of these congeners was not dose dependent when the two doses administered were compared.

Triacylglycerol biosynthetic enzymes in lean and obese Zucker rats

In the present investigation, we have compared the potential of triacylglycerol formation from sn-glycerol-3-phosphate (GP) and 2-monoacylglycerol (MG) in liver, adipose tissue and intestine from lean and obese Zucker rats. Microsomal fractions were used to measure the sn-glycerol-3-phosphate acyltransferase (GPAT), diacylglycerol acyltransferase (DGAT) and monoacylglycerol acyltransferase (MGAT) activities and homogenates were used to measure NEM-sensitive and NEM-insensitive phosphatidate phosphohydrolase (PPH) activities. In adipose tissue and liver, the GP pathway served as the major route of glycerolipid formation, with adipose tissue being 5-20-fold more active. The activities of the GP pathway enzymes increased further in response to obesity, with some degree of organ specificity. In adipose tissue of obese rats, the activities of all the pathway enzymes increased; whereas, in liver and intestine, this response was limited to PPH and GPAT, respectively. In contrast with the GP pathway enzymes, obesity in Zucker rats was not associated with alterations in the acylation of 2-monoacylglycerol. Comparison of the activities of MGAT in different intestinal segments indicated that the MG pathway was most active in the jejunum and least active in the ileum and that this pattern did not change in response to obesity. These measurements of the individual enzyme reactions provide evidence that the entire process of esterification via sn-glycerol-3-phosphate is accelerated in the various organs from obese rats and that this perturbation in lipid metabolism may contribute significantly to the increased deposition of body fat noted in this animal model.

Properties of monoglycerol acyltransferase in rat adipocytes.

Previous studies by Coleman and Haynes (1986, J. Biol. Chem. 261, 224-228) indicated the presence of two different tissue specific monoacylglycerol acyltransferases (MGAT) in intestinal mucosa and suckling rat liver. The evidence was based upon the differential responses of these two isoenzymes to various treatments including, the effects of temperature, proteolysis, protein modification reagents, detergents, and divalent cations. In the present investigation, we have used some of these criteria to determine the identity of adipose enzyme with the MGAT present in liver and intestinal microsomes. The properties of adipose and intestinal enzymes were similar in several respects, but differed from the liver enzyme. This suggests the possibility that MGAT activities from adipose and intestine may be mediated by the same enzyme protein, whereas the liver MGAT may be a separate isoenzyme as proposed earlier. The most distinguishing feature of the liver enzyme was its ability to sustain both high temperature (52 degrees C) and resist proteolysis. However, when disrupted microsomal preparations were used, the liver enzyme was both thermolabile and protease sensitive, as observed for the intestinal and adipose MGAT. Possibly, the location of liver MGAT within the membranes may be responsible for such unique properties of liver MGAT.

Pharmacokinetics and pharmacodynamics of pipecuronium bromide (Arduan) in elderly surgical patients

The neuromuscular response to pipecuronium bromide (Arduan), 70 μg/kg, was studied in 20 elderly (>70 yr) and 10 younger Patients (<60 Yr) during nitrous oxide, fentanyl, and droperidol anesthesia. The adductor Pollicis response to single 0.2-ms suparamaximal pulses was recorded. Although all younger patients were completely paralyzed, 2 of 20 elderly patients did not attain paralysis. Onset time in the elderly was prolonged (6.9 ± 2.6 vs 4.3 ± 1.5 min, P < 0.02). Spontaneous recovery was similar in both groups, with 75% recovery occurring at 133 ± 52 min in the elderly and 146 ± 46 min in the younger patients. The pharmacokinetic variables were similar for the two groups, and pharmacodynamic analysis revealed a similar sensitivity at the neuromuscular junction. The pharmacologic actions of pipecuronium in otherwise healthy patients do not differ between young and elderly adults.

Cardiac performance preserved despite thiopental loading.

BackgroundSome cerebral artery aneurysms require cardiopulmonary bypass and deep hypothermic circulatory arrest to be clipped safely. During bypass these neurosurgical patients often are given large doses of thiopental in the hope that additional cerebral protection will be provided. However, thiopental loading during bypass has been associated with subsequent cardiac dysfunction in patients with heart disease. This study was undertaken to determine how patients without concomitant heart disease would respond to thiopental loading. MethodsTwenty-four neurosurgical patients with giant cerebral aneurysms and little or no cardiac disease were anesthetized with fentanyl, nitrous oxide, and isoflurane. Thiopental was titrated to achieve electroencephalographic burst-suppression before bypass, and the infusion was continued until after separation. Prebypass hemodynamic and echocardiographic measurements were obtained during a stable baseline and 15 min after thiopental loading began. They were repeated after bypass. ResultsPrebypass thiopental loading increased heart rate from 61 ± 11 to 72 ± 13 beats/min and decreased stroke volume from 43 ± 10 to 38 ± 8 ml. beat−1. m-2, but arterial and filling pressures, vascular resistance, cardiac index, and ejection fraction remained the same. Before bypass, thiopental plasma concentration measured 28 ± 8

The role of catecholamines in cocaine toxicity: A model for cocaine “sudden death”

mUg/ml. Loading continued for 2–3 h until after bypass was terminated, and the overall infusion rate was 18 ± 5 mg. kg−1. h−1. All patients were easily separated from bypass without inotropic support. Following bypass, vascular resistance was decreased; heart rate, filling pressures, and cardiac index were increased; stroke volume had returned to its baseline; and ejection fraction was unchanged. ConclusionsIt was concluded that if preoperative ventricular function is good, thiopental loading to electroencephalographic burst-suppression causes negligible cardiac impairment and does not impede separation from cardiopulmonary bypass.

Aging alters the pharmacokinetics of pyridostigmine

Sudden death associated with cocaine abuse is preceded by a state of agitated delirium. We postulated that release of catecholamines associated with this stress enhanced toxicity from cocaine. Thus we investigated the effect of catecholamine infusion [(epinephrine (7.25 ugml-1), norepinephrine (4.4 ugml-1) and dopamine (8.0 ugml-1), infused at 6 ml h-1] on the toxicity from concomitant infusion of cocaine (1 mg-kg-1 min-1). Two groups of rats were studied in order to isolate distinct toxicity endpoints: convulsions and respiratory arrest in conscious, and, circulatory arrest in anesthetized and ventilated rats. Catecholamines were administered at either full or 1/2 strength to establish a dose response effect on cocaine toxicity. Catecholamine infusion in a dose dependent fashion provoked earlier convulsions and respiratory arrest in conscious rats and circulatory arrest in anesthetized and ventilated rats. Despite lower cocaine cumulative dose administration, rats receiving catecholamines had similar plasma cocaine concentrations at the onset of convulsions and respiratory arrest compared to those with cocaine infusion alone. The data suggest that catecholamines enhance the convulsive, respiratory and circulatory toxicity of cocaine by a pharmacokinetic interaction.

Glycerolipid biosynthesis in rat adipose tissue 12. Properties of Mg2+-dependent and -independent phosphatidate phosphohydrolase

The duration of the antagonism to neuromuscular blockade produced by pyridostigmine is prolonged in elderly patients, and a pharmacokinetic explanation was sought.Ten elderly (71-85 yr) and 10 younger (21-51 yr) patients were anesthetized with thiopental, nitrous oxide, and isoflurane and paralyzed with a combination of d-tubocurarine and pancuronium. When twitch height returned to 5% of baseline, pyridostigmine 0.25 mg/kg was administered and blood samples were collected intermittently for 6 h. Pyridostigmine plasma concentrations were determined by radioimmunoassay and after an hour were always greater in the elderly than in the younger patients. In both groups, plasma pyridostigmine decrement curves were best described by triexponential equations. Pharmacokinetic analysis revealed that plasma clearance in the elderly group was significantly decreased compared to that in the younger group (6.7 +/- 2.2 vs 9.5 +/- 2.7 mL centered dot kg-1 centered dot min-1, P < 0.05). Elimination half-lives and volumes of distribution were not significantly different between groups. We conclude that a possible explanation for the prolonged duration of action of pyridostigmine in the elderly is its slow plasma clearance. (Anesth Analg 1995;81:773-6)