Biomedical subjects
Publications and source records attributed to G Bianchetti.
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The distribution and kinetics of D,L-propranolol in rat brain were examined after an intravenous injection of the drug. Measurements in brain areas and blood were performed by means of a sensitive and specific gas liquid chromatographic method. The disappearance rate in cortical areas paralleled that in blood. However D,L-propranolol decreased at a slower rate in hypothalamic and medullary nuclei. Since propranolol is believed to have central hypotensive effects, its retention by certain central nuclei involved in blood pressure regulation is of interest.
Plasma levels of haloperidol were monitored in children and teenagers suffering from psychotic episodes and/or abnormal movements (tics and Gilles de la Tourette's syndrome). Steady-state concentrations of haloperidol ranged from 0.7 to 19 ng/ml without any apparent relationship with the administered dose (15--285 micrograms/kg/day) and a 15-fold variability was observed for the same daily dosage. On the contrary, a significant (p < 0.02) relationship was found between the age of the patients and the plasma concentrations to dose ratios, lower values being present in younger patients. Side effects too appeared to be related to plasma levels, with a significant increase (p < 0.01) in incidence for concentrations over 6 ng/ml. In most of the cases suffering from tics and Gilles de la Tourette's syndrome, a positive response was associated with plasma levels of 1--4 ng/ml, while no relationship could be established for the psychotic group. The relevance of monitoring plasma drug levels when prescribing haloperidol in pediatrics is discussed.
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A sensitive gas-chromatographic method for quantitative analysis of haloperidol in human plasma is described. The use of nitrogen-phosphorus selective detection reduces the time required for analysis. Azaperone is used as the internal reference standard. The method is suitable for the determination of haloperidol plasma levels in patients treated with doses ranging from 1.2 to 200 mg/day. No interference from drugs needed in the associated antipsychotic therapy has been found. The simplicity, specificity and sensitivity of the method make it suitable for routine analysis of haloperidol plasma levels in psychotic patients undergoing chronic treatment.
A procedure is described for the determination of tiflorex and its metabolite nortiflorex in biological specimens. The compounds are converted into their trichoroacetyl derivatives, which are separated on a glass column packed with 3% OV-17 on Gas-Chrom Q, and measured with an electron-capture detector. The mechanism was investigated by gas chromatography-mass spectrometry. The method is rapid, sensitive for concentrations of 1 ng/ml and has been used to measure tiflorex and its metabolite in rat plasma after intravenous administration and in human volunteers after administration by the oral route.
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Heart-rate, arterial pressure, and plasmarenin activity were determined in six normal subjects at rest and after an injection of 8 microgram isoprenaline with and without prior propranolol administered orally in a dose of 5 mg 8-hourly for a total of five doses. After propranolol, resting heart-rate, systolic pressure, and plasma-renin activity all fell significantly (P less than 0.05 to less than 0.001). When the isoprenaline-induced changes of heart-rate, diastolic pressure, and plasma renin activity without propranolol were compared to those with propranolol, these responses were greatly diminished (P less than 0.01 to less than 0.001). The percent blockade by propranolol of the isoprenaline-induced changes ranged from 65% for diastolic pressure to 77% for heart rate and 78% for plasma-renin activity. Propranolol levels determined by conventional fluorometry were below accurate detection limits, whereas those determined by gas-liquid chromatography ranged from 2.3 to 8.5 ng/ml. These findings, which demonstrate beta-blockade with low-dose propranolol, are not consistent with the existence of a postulated threshold for the hepatic "first-pass effect" in man, which is said to require saturation by single doses of 30 mg or more before propranolol enters the systemic circulation.
Low-molecular weight dialysable peptides, obtained by plasmin degradation of purified bovine fibrinogen preparations, have been shown to increase the chronotropic activity of isolated rat atria. This effect was dose dependent and was inhibited by inhibitors of glycolysis (NaF and 2-deoxy-D-glucose), but not by an inhibitor of oxidative phosphorylation (2, 4-dinitrophenol). Propranolol, a beta-blocking agent, was also ineffective. Fibrinogen-derived peptides increased both cAMP levels and phosphorylase alpha activity in stimulated atria. The increase of these parameters was transitory and appeared to precede the occurrence of the positive chronotropic effect. In the test situation used, the biochemical and functional modifications induced by fibrinogen-derived peptides were similar to those induced by glucagon.
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