Plasma concentrations and sedative effects of a dexmedetomidine, midazolam, and butorphanol combination after transnasal administration in healthy rabbits.

Plasma concentrations of dexmedetomidine (D = 0.1 mg/kg), midazolam (M = 2 mg/kg), and butorphanol (B = 0.4 mg/kg) were analyzed by liquid chromatography-mass spectrometry (LC-MS/MS) after their simultaneous (DMB) transnasal (TN) administration to healthy rabbits. Time-dependent changes in sedation and antinociception were evaluated by measuring a sedation score based on rabbit's posture, loss of the righting, palpebral and pedal withdrawal reflexes and by instrumental monitoring of rectal temperature, heart rate, arterial blood pressure, pulse-oximetry, and capnometry. The peak plasma concentration (Cmax ) of each drug was reached within 5 min (Tmax ) from DMB-TN administration along with deep sedation and analgesia. Such effects subsided after 45 min into a moderate sedation and analgesia lasting for additional 15 min. All rabbits awakened spontaneously and uneventfully 90 min after DMB-TN administration. During the anesthetic procedure, arterial blood pressure markedly decreased and respiratory depression ensued requiring oxygen supplementation. The results of this study show that all three molecules of the DMB combination were absorbed through the TN route, inducing deep sedation and analgesia suitable for minor surgical procedures. Such combination should be used with caution in rabbits bearing cardiovascular or respiratory diseases because of its ability to induce hypotension and respiratory depression.

Prolactin hyperresponsiveness to D-fenfluramine in drug-free schizophrenic patients: a placebo-controlled study.

BACKGROUND: Functional alterations in the central serotonergic system have been reported in schizophrenia but no conclusive data have been provided. In the present study, we investigated the prolactin (PRL) response to the selective serotonin (5-HT) releasing agent D-fenfluramine in both patients with schizophrenia and matched healthy subjects. METHODS: Sixteen drug-free schizophrenics and 16 healthy subjects were randomized in a double-blind neuroendocrine test to D-fenfluramine (30 mg p.o.) or placebo. Blood PRL and cortisol concentrations were determined by radioimmunoassay, while plasma levels of D-fenfluramine were measured by mass spectrometry. RESULTS: In schizophrenic patients, baseline plasma PRL levels were not different from controls, whereas plasma cortisol concentrations were significantly increased (p < .03). The PRL response to D-fenfluramine was significantly enhanced in patients as compared to matched control subjects (p < .005). Schizophrenics meeting Kane's criteria for previous nonresponse to typical neuroleptics exhibited a PRL response to D-fenfluramine significantly higher than non-drug-resistant patients (p < .04). No significant difference in plasma D-fenfluramine concentrations was observed between schizophrenic and healthy subjects. CONCLUSIONS: These findings suggest a serotonergic hypersensitivity in chronic schizophrenia. This alteration seems to be peculiar to those patients refractory to typical neuroleptics.

Suppression of nocturnal plasma melatonin levels by evening administration of sodium valproate in healthy humans.

To investigate the role of gamma-aminobutyric acid (GABA) in the modulation of human melatonin production, we studied the effects of the acute administration of the GABAergic drug, sodium valproate (VAL), on nocturnal blood melatonin levels in healthy subjects. To this purpose, 4 healthy men and 3 healthy women, aged 24-33 years, underwent three experimental sessions in which they received orally 400 mg VAL, 800 mg VAL, or placebo, in random order, according to a double-blind design. The drug administration was done at 19:00 hours; thereafter, blood samples were collected over the night, in dark conditions with the help of a red light. As compared to placebo, VAL, at the dosage of both 400 and 800 mg, significantly suppressed nocturnal blood melatonin levels, the higher dose being slightly more effective than the lower one. The maximum suppression coincided with the highest plasma levels of valproic acid. These findings support the view that endogenous GABA may participate in the modulation of the activity of the human pineal gland.

A new method for the determination in blood and urine of a novel triazolobenzodiazepine (estazolam) by HPLC.

In this study the authors report a new method to determine estazolam in blood and urine by high pressure liquid chromatography (HPLC). This compound is a triazolobenzodiazepine and shows an interesting psychopharmacological activity. The extraction from biological fluids was carried out using a mixture of ethylenechloride, methylenechloride, and ethylacetate (1:1:8). The HPLC analysis was carried out with a C18 column, using methanol:phosphate buffer (pH 7.5, 0.011M):acetonitrile (65:33:2) as mobile phase. The detector was set at lambda = 240 nm. The method shows good repeatability and a linear response in the range of 0.6 to 10 micrograms estazolam/mL both in serum and urine. A case of non-lethal acute intoxication in which the method was applied is also reported.