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Biomedical subjects

G Bianchetti

Publications and source records attributed to G Bianchetti.

At least 73 records · Page 4Linked to original sources
PubMed1980

Pharmacokinetics of indomethacin in the premature infant.

Indomethacin (I) pharmacokinetics was evaluated in 6 premature infants who received the drug for treatment of patent ductus arteriosus. Administered by oral or rectal route, I (0.2 mg/kg/24 h X 3) was promptly absorbed with peak plasma concentrations attained within 1 and 3 h. The elimination of I appeared to follow two compartment open model kinetics, with terminal plasma half-lives ranging from 30 to 90 h. Apparent plasma clearance values were between 0.076 and 0.335 ml/min/kg. Ductal closure was observed in 4 of the 6 infants. Data point to a possible relationship between therapeutic effects and I plasma concentrations.

Creatinine↗
PubMed1980

Kinetics of distribution of di-propranolol in various organs and discrete brain areas of the rat.

The kinetics of distribution of di-propranolol (P) to various organs and tissues were studied in the rat after an i.v. dose of 2 mg/kg. The disposition of the drug can be adequately described by a two-compartment open model with a distribution half-life of 4.8 min, a terminal blood half-life of 63 min and an apparent volume of distribution beta of 8.5 liters/kg. Higher tissue concentrations were found to be present in heart, brain and kidney. Although the disappearance rate of P from abdominal aorta, muscles, adipose tissue and whole brain paralleled that of blood, the elimination rate constant for atria and kidney was significantly reduced suggesting a specific binding of P. After an i.v. dose of 5 mg/kg, P distributed rapidly to various brain areas following a vascularity pattern with higher concentrations in cortical areas of earlier times. An equilibrium between various brain areas was observed at 2 to 3 hr after dosing. There was a parallel decay of P concentrations in the blood and in cortical areas, whereas the elimination constants were significantly reduced for hypothealamic nuclei and the medulla (C1 and C2), suggesting again a specific binding. The data show that distribution, uptake and tissue binding of P in various peripheral organs and discrete brain areas is not a uniform process and they could give a partial explanation on the discrepancies observed clinically between the pharmacodynamics and pharmacokinetics. The data also suggest the possibility of specific P binding sites in heart, kidney and brain which could be of relevance for its mode of action.

Animals↗
PubMed1980

Influence of route of administration on haloperidol plasma levels in psychotic patients.

Haloperidol plasma concentrations were determined in psychotic patients to whom the drug was given by three different routes of administration (i. v. perfusion, intramuscularly and orally). When measured 15 hours after the last administration, a significant difference (p < 0,001) was found in the steady state plasma concentration between the oral and the i.m. route. The values were higher after intramuscular administration and were subject to less interindividual fluctuation than after the oral. The reduction in plasma levels after oral administration in respect to i.m. were in accordance with the bioavailability of haloperidol. The opportunity of switching from oral to intramuscular treatment is discussed.

Administration, Oral↗
PubMed1979

Brain distribution of propranolol in the rat.

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.

Animals↗
PubMed1979

Haloperidol plasma level monitoring in pediatric patients.

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.

Adolescent↗
PubMed1978

Rapid and sensitive method for determination of haloperidol in human samples using nitrogen-phosphorus selective detection.

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.

Chromatography, Gas↗
PubMed1978

Quantitative determination of tiflorex in human fluids using electron-capture detection.

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.

Animals↗
PubMed1978

Beta-blockade and blood-levels after low-dose oral propranolol: The hepatic "first-pass" threshold revisited.

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.

Administration, Oral↗
PubMed1977

Plasma concentrations and cardiotoxic effects of desipramine and protriptyline in the rat.

1 Desipramine and protriptyline were administered to anaesthetized rats by two consecutive intravenous infusions in order to obtain a peak level (first infusion) followed by lower steady state concentrations (second infusion) (Wagner, 1974). Theoretical plasma level time courses were confirmed experimentally.2 Desipramine and protriptyline were measured in atria and ventricles. Increasing infusion rates led to proportional increases in plasma and atrial concentrations. The tissue/medium ratio ranged from 57 to 21 for desipramine and from 43 to 11 for protriptyline according to the time of determination during infusions.3 Heart rate changes, deviation of the electrical axis of the heart and prolongation of atrioventricular conduction were recorded at fixed times during infusion.4 Positive chronotropic effects were noted at plasma concentrations ranging from 0.035 to 0.1 mug/ml for desipramine and from 0.04 to 1.2 mug/ml for protriptyline. At higher plasma concentrations the positive chronotropic effect decreased and bradycardia developed. Both drugs induced right rotation of the electrical axis of the heart. Threshold plasma levels giving 40 degrees rotation were 1.35 mug/ml (desipramine) and 1.75 mug/ml (protriptyline). Atrioventricular conduction was prolonged at threshold plasma concentrations of 2.2 mug/ml for desipramine and 3.6 mug/ml for protriptyline.5 Desipramine is more cardiotoxic than protriptyline. This difference is discussed in relation to the plasma and heart concentration of the two drugs.

Animals↗
PubMed1976

Gas chromatographic determination of acenocoumarin in human plasma.

A method based on solvent extraction, formation of a fluorinated derivative and quantitation by gas-liquid chromatography with electron-capture detection has been developed for the determination of acenocoumarin in plasma. The specificity and sensitivity of the procedure appear to be satisfactory for drug level measurements in human plasma. Its relative simplicity permits its use in routine analysis.

Acenocoumarol↗