Exploration of the bovine colostrum proteome and effects of heat treatment time on colostrum protein profile

Heat treatment of colostrum is performed on modern dairy farms to reduce pathogenic contamination before hand-feeding the colostrum to newborn calves; however, limited data are available concerning effects of heat treatment on biologically active proteins in colostrum. The objective of this exploratory study was to investigate effects of heat treatment and length of heat treatment on colostrum protein profile. Colostrum samples were collected from Holstein cows within 12 h after parturition and assigned to the following groups: heat treatment at 60°C for 0 (untreated control), 30, 60, or 90 min. Samples were fractionated using acid precipitation, followed by ultracentrifugation and ProteoMiner (Bio-Rad Laboratories, Hercules, CA) treatment, and tandem-mass tagging was used to comparatively assess the low abundance protein profile. A total of 162 proteins were identified with more than 2 peptides in the low abundance protein enriched fraction. Of these, 62 differed in abundance by more than 2-fold in heat treated samples compared with the unheated control. The majority of proteins affected by heat treatment were involved in immunity, enzyme function, and transport-related processes; affected proteins included lactadherin, chitinase-3-like protein 1, and complement component C9. These results provide a foundation for further research to determine optimum heat treatment practices to ensure newborn calves are fed colostrum-containing proteins with the highest nutritional and biological value.

Control of cell migration direction by inducing cell shape asymmetry with patterned topography

In this study, we explored the concept of introducing asymmetry to cell shapes by patterned cell culture substrates, and investigated the consequence of this induced asymmetry to cell migration behaviors. Three patterns, named "Squares", "Grating", and "Arcs" were fabricated, representing different levels of rotational asymmetry. Using time-lapse imaging, we systematically compared the motility and directionality of mouse osteoblastic cells MC3T3-E1 cultured on these patterns. Cells were found to move progressively faster on "Arcs" than on "Grating", and cells on "Squares" were the slowest, suggesting that cell motility correlates with the level of rotational asymmetry of the repeating units of the pattern. Among these three patterns, on the "Arcs" pattern, the least symmetrical one, cells not only moved with the highest velocity but also the strongest directional persistence. Although this enhanced motility was not associated with the detected number of focal adhesion sites in the cells, the pattern asymmetry was reflected in the asymmetrical cell spreading. Cells on the "Arcs" pattern consistently displayed larger cytoplasmic protrusion on one side of the cell. This asymmetry in cell shape determined the direction and speed of cell migration. These observations suggest that topographical patterns that enhance the imbalance between the leading and trailing fronts of adherent cells will increase cell speed and control movement directions. Our discovery shows that complex cell behaviors such as the direction of cell movement are influenced by simple geometrical principles, which can be utilized as the design foundation for platforms that guide and sort cultured cells.

Potential-based methodology for active sound control in three dimensional settings

This paper extends a potential-based approach to active noise shielding with preservation of wanted sound in three-dimensional settings. The approach, which was described in a previous publication [Lim et al., J. Acoust. Soc. Am. 129(2), 717-725 (2011)], provides several significant advantages over conventional noise control methods. Most significantly, the methodology does not require any information including the characterization of sources, impedance boundary conditions and surrounding medium, and that the methodology automatically differentiates between the wanted and unwanted sound components. The previous publication proved the concept in one-dimensional conditions. In this paper, the approach for more realistic conditions is studied by numerical simulation and experimental validation in three-dimensional cases. The results provide a guideline to the implementation of the active shielding method with practical three-dimensional conditions. Through numerical simulation it is demonstrated that while leaving the wanted sound unchanged, the developed approach offers selective volumetric noise cancellation within a targeted domain. In addition, the method is implemented in a three-dimensional experiment with a white noise source in a semi-anechoic chamber. The experimental study identifies practical difficulties and limitations in the use of the approach for real applications.

Estradiol rapidly modulates odor responses in mouse vomeronasal sensory neurons

In rodents, many social behaviors are driven by the sense of smell. The vomeronasal organ (VNO), part of the accessory olfactory system mediates many of these chemically driven behaviors. The VNO is heavily vascularized, and is readily accessible to circulating peptide or steroid hormones. Potentially, this allows circulating hormones to alter behavior through modulating the output of the primary sensory neurons in the VNO, the vomeronasal sensory neurons (VSNs). Based on this, we hypothesized that steroid hormones, in particular 17β-estradiol, would modulate activity of VSNs. In this paper, we show that the estrogen receptors, GPR30 and ERα, were present in VSNs and that estradiol may be synthesized locally in the VNO. Our results also showed that 17β-estradiol decreased responses of isolated VSNs to dilute urine, a potent natural stimulus, with respect to current amplitudes and depolarization. Further, 17β-estradiol increased the latency of the first action potential (AP) and the AP amplitude. Additionally, calcium responses to sulfated steroids (present in the low molecular weight fraction of urine) that act as ligands for apical vomeronasal receptors were decreased by 17β-estradiol. In conclusion, we show that estradiol modulates odorant responses mediated by VSNs and hence paves the way for future studies to better understand the mechanisms by which odorant mediated behavior is altered by endocrine status of the animal.

Multi-domain active sound control and noise shielding

This paper describes an active sound control methodology based on difference potentials. The main feature of this methodology is its ability to automatically preserve "wanted" sound within a domain while cancelling "unwanted" noise from outside the domain. This method of preservation of the wanted sounds by active shielding control is demonstrated with various broadband and realistic sound sources such as human voice and music in multiple domains in a one-dimensional enclosure. Unlike many other conventional active control methods, the proposed approach does not require the explicit characterization of the wanted sound to be preserved. The controls are designed based on the measurements of the total field on the boundaries of the shielded domain only, which is allowed to be multiply connected. The method is tested in a variety of experimental cases. The typical attenuation of the unwanted noise is found to be about 20 dB over a large area of the shielded domain and the original wanted sound field is preserved with errors of around 1 dB and below through a broad frequency range up to 1 kHz.

Biochemical characterization of the cell-biomaterial interface by quantitative proteomics

Surface topography and texture of cell culture substrata can affect the differentiation and growth of adherent cells. The biochemical basis of the transduction of the physical and mechanical signals to cellular responses is not well understood. The lack of a systematic characterization of cell-biomaterial interaction is the major bottleneck. This study demonstrated the use of a novel subcellular fractionation method combined with quantitative MS-based proteomics to enable the robust and high-throughput analysis of proteins at the adherence interface of Madin-Darby canine kidney cells. This method revealed the enrichment of extracellular matrix proteins and membrane and stress fibers proteins at the adherence surface, whereas it shows depletion of extracellular matrix belonging to the cytoplasmic, nucleus, and lateral and apical membranes. The asymmetric distribution of proteins between apical and adherence sides was also profiled. Apart from classical proteins with clear involvement in cell-material interactions, proteins previously not known to be involved in cell attachment were also discovered.

MONITORING THE SEROLOGICAL PROTEOME: THE LATEST MODALITY IN PROSTATE CANCER DETECTION

PURPOSE

Various strategies have recently emerged to improve the diagnostic prediction of prostate cancer (CaP). One such strategy includes the mass profiling of serum protein fractions selectively adsorbed onto chemically modified probes. In the current study we further validated this approach, while offering a more versatile, less expensive and yet equally predictive alternative to existing technologies.

MATERIALS AND METHODS

A solid core lipophilic C-18 resin was used to extract and enrich the low molecular weight protein fraction from patient serum for further analysis by mass spectrometry. Mass spectra generated from a 48 patient training set were data mined using multivariate analysis to identify diagnostically significant protein peaks. These peaks were then used to test a blinded study set comprising 168 patients with common statistical algorithms and commercially available software packages.

RESULTS

A total of 36 peaks generated from the training set were used to test the combined set of 168 serum samples obtained from 98 healthy individuals and 70 patients with CaP. We report a sensitivity of 94.1% and a specificity of 99.0% with 1 false-positive, 4 false-negative and 5 nondiagnosed cases.

CONCLUSIONS

Our results further indicate that mass profiling of serological proteins provides a means for the accurate detection of CaP. In addition, our approach was found to be superior to chip based protocols, generating rich, sharp, highly reproducible spectra attainable in a high throughput manner and at minimal cost. This technique is also scaleable for subsequent protein characterization using multidimensional protein identification technologies. Finally, analyses of mass spectra with commercially available statistical applications was found to be highly effective in generating highly discriminatory m/z values for CaP diagnosis.

The immunostimulatory activity and stability of grass carp (Ctenopharyngodon idellus) roe lectin

A hexameric rhamnose-specific lectin with a molecular mass of 205kDa and exhibiting some N-terminal sequence similarity to other fish lectins was isolated from roe of the grass carp (Ctenopharyngodon idellus) by affinity chromatography on rhamnose-Sepharose and ion exchange chromatography by fast protein liquid chromatography on a Mono S column. The lectin exhibited mitogenic activity toward murine splenocytes with a potency lower than that of the plant lectin ConA. It exerted a stimulatory effect at a concentration of 10 micro g/ml on the phagocytic activity of seabream (Sparus sarba) macrophages. It was unstable toward heat (temperature > or =40 degrees C), acid (0.1M HCl), alkali (0.1M NaOH), trypsin and succinylation.

Purification and characterization of a rhamnose-binding lectin with immunoenhancing activity from grass carp (Ctenopharyngodon idellus) ovaries

A rhamnose-specific lectin was isolated from ovaries of the grass carp (Ctenopharyngodon idellus). The grass carp lectin possesses a molecular mass of 205 kDa. It is composed of six subunits each with a molecular mass of 35 kDa. The N-terminal amino acid sequence of the grass carp shows similarity to those of other fish species with 26-35% amino acid identity. It is mitogenic toward murine splenocytes and peritoneal exudate cells.

Reversible metabolism of drugs

Many drugs undergo reversible metabolism. The basis of our understanding of this process is the reversible metabolism of prednisone (PD)-prednisolone (PL). The pharmacokinetics of reversible metabolism requires the use of four area under the curve values integrated into four equations for clearance (CL). Other variables, such as linear versus non-linear disposition, can play important roles in reversible metabolism. Of recent interest is the reversible metabolism of haloperidol which consists of an interconversion process between the parent drug haloperidol (HL) and its reduced metabolite (RH). However, the interconversion of HL-RH differs from the PD-PL model in that, whereas PD and PL are both active, RH is considered to be a therapeutically inactive, possibly toxic, metabolite. This article reviews the pharmacodynamic and pharmacokinetic properties of HL and RH and the possible clinical effects that can result from this reversible metabolism.

Solenin, a novel protein with translation-inhibiting activity from the traditional Chinese medicinal fish, the sea dragon Solenognathus hardwickii

A single-chained protein designated solenin was isolated from Solenognathus hardwickii, a fish used as traditional Chinese medicinal material. Solenin was capable of inhibiting translation in a cell-free rabbit reticulocyte lysate system with an IC(50) of 2 microM and expressing a ribonuclease activity of 0.8U/mg toward yeast transfer RNA, but it lacked N-glycosidase activity characteristic of ribosome inactivating proteins Solenin exhibited a molecular weight of 18kDa and possessed an N-terminal sequence AHDAEVNEVKAQVAA. The protein was adsorbed on three types of chromatographic media: Affi-gel blue gel, CM-Sepharose and Mono S. It was devoid of antifungal and lectin activities.

Lack of CYP3A4 inhibition by grapefruit juice and ketoconazole upon clozapine administration in vivo

The drug-food and drug-drug interaction between grapefruit juice (GFJ) and ketoconazole (KETO) was evaluated in schizophrenic patients given a single dose of clozapine (CLZ). CLZ is metabolized primarily by CYP isozymes 3A4 and 1A2 to two principal metabolites, desmethylclozapine (DCLZ) and clozapine N-oxide (CNO). GFJ and KETO are well known potent CYP 3A4 inhibitors in the gastrointestinal tract and hepatic isozymes, respectively. Twenty-one schizophrenic patients participated in the co-administration of CLZ 50 mg and GFJ. After a one-week washout, five patients were given double the GFJ (HGFJ) dose for 7 consecutive days. In another group of five patients, ketoconazole (KETO) 400 mg was given for 7 consecutive days. At the end of the 7-day period for both groups, CLZ was coadministered with the HGFJ and KETO groups. CLZ, DCLZ and CNO were assayed by HPLC. GFJ, HGJF and ketoconazole failed to significantly change CLZ disposition. Metabolites DCLZ and CNO concentrations remained unchanged during the study. The only exception was decreased Cmax in DCLZ and CNO concentrations. These results indicate that CYP 3A4 inhibition may not be clinically significant compared to CYP 1A2, as previous studies show a dramatic increase in CLZ plasma concentrations with fluvoxamine (CYP 1A2 inhibitor). The reasons for the lack of drug-food and drug-drug interactions with CLZ and CYP 3A4 inhibitors can be explained by the higher Ki values for gastrointestinal and hepatic CYP 3A4 isozymes.

Isolation of a novel agglutinin with complex carbohydrate binding specificity from fresh fruiting bodies of the edible mushroom Lyophyllum shimeiji

A hemagglutinin, with a molecular weight of 30,000 and expressing hemagglutinating activity which could not be inhibited by simple sugars and glycoproteins, was isolated from fresh fruiting bodies of the edible mushroom Lyophyllum shimeiji. The protein was adsorbed on CM-Sepharose even in 20 mM ammonium acetate (pH 5.5) containing 1 M NaCl and was desorbed by 20 mM ammonium bicarbonate (pH 9). The hemagglutinating activity was subsequently adsorbed on Mono S in 20 mM ammonium acetate (pH 5.5) and was desorbed by a linear gradient of 0.2-0.5 M NaCl in ammonium acetate buffer. The hemagglutinin exhibited a novel N-terminal sequence not found in any lectin and hemagglutinin reported so far. It was devoid of antifungal activity.

Antiproliferative and antimitogenic activities in a peptide from puffball mushroom Calvatia caelata

A peptide with a molecular weight of 8 kDa and an N-terminal sequence closely resembling that of ubiquitin was isolated from fruiting bodies of the mosaic puffball mushroom Calvatia caelata. The peptide was purified using a protocol that involved ion-exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, and ion-exchange chromatography on Mono S. The peptide inhibited translation in the cell-free rabbit reticulocyte lysate system and exhibited N-glycosidase activity. It potently inhibited proliferation of spleen cells with an IC(50) of about 100 nM as indicated by the suppression of [methyl-(3)H]thymidine uptake. The viability of breast cancer cells was reduced to half at a ubiquitin concentration of about 100 nM.

A monomeric mannose-binding lectin from inner shoots of the edible chive (Allium tuberosum)

A mannose-binding lectin was isolated from the inner shoots of the chive Allium tuberosum. The procedure involved aqueous extraction, (NH4)2SO4 precipitation, dialysis to remove (NH4)2SO4, affinity chromatography on mannose-agarose, ion exchange chromatography on SP-Sepharose, gel filtration on Superdex 75, and ion exchange chromatography on Mono S. Lectin activity was adsorbed on mannose-agarose, SP-Sepharose, and Mono S. The lectin demonstrated a molecular weight of 13 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, indicating that it is a single-chain protein. N-terminal sequence analysis revealed its remarkable homology to Allium cepa lectin and similarity to a lesser extent to lectins from members of the Amaryllidaceae, Orchidaceae, and Liliaceae. The lectin manifested mitogenic activity in murine splenocytes and inhibitory activity against human immunodeficiency virus type 1 reverse transcriptase.

Branded versus generic clozapine: bioavailability comparison and interchangeability issues

Clozapine has been the treatment of choice for patients with refractory schizophrenia. Generic clozapine has recently become available, because of a waiver of the usual criteria for establishing bioequivalence. However, there are biopharmaceutical, bioavailability, and clinical concerns related to the generic formulation raised by both clinicians and academic researchers. We conducted a prospective, randomized, crossover study to evaluate steady-state pharmacokinetics, pharmacodynamics, and tolerability of generic clozapine (Zenith Goldline Pharmaceuticals) versus Clozaril (Novartis Pharmaceuticals) in schizophrenic patients. A preliminary report of the pertinent bioavailability results is presented here. Despite comparable mean plasma concentration-time curves, significant differences were found in the primary pharmacokinetic parameters of the 2 formulations in almost 40% of patients. Such intraindividual differences raise the issue of average bioequivalence versus individual bioequivalence and the implication for interchangeability of different clozapine formulations. The decision to switch a patient from branded to generic clozapine should be made on an individual basis with special emphasis on clinical outcome, and patients should be monitored closely during the transition.

A robust cysteine-deficient chitinase-like antifungal protein from inner shoots of the edible chive Allium tuberosum

From the inner shoots of the chive Allium tuberosum, a single-chained protein with a molecular weight of 36 kDa and an N-terminal sequence manifesting resemblance to chitinases but lacking in cysteine residues characteristic of a cysteine-rich domain present in chitinases of other Allium species, was purified. The isolation procedure entailed affinity chromatography on Affi-gel blue gel, ion-exchange chromatography on DEAE-cellulose and Mono S, and gel filtration on Superdex 75. The protein was unadsorbed on DEAE-cellulose and adsorbed on Affi-gel blue gel and Mono S. It exhibited antifungal activity against Rhizoctonia solani, Fusarium oxysporum, Coprinus comatus, Mycosphaerella arachidicola, and Botrytis cinerea. The IC(50) for its antifungal effect against Botrytis cinerea was 0.2 microM. The antifungal activity was stable after 1 h at pH 1.6 and 12.3, and up to 60 degrees C for 5 min. Incubation of the protein with trypsin or chymotrypsin at an enzyme:substrate ratio of 1:100 and pH 7.6 up to 150 min did not affect its antifungal activity. The protein did not exhibit antibacterial activity. The protein inhibited cell-free translation in a rabbit reticulocyte system with an IC(50) of 0.8 microM, but did not affect the proliferation of mouse splenocytes. It exerted some cytotoxic effect on breast cancer cells and was inhibitory toward HIV-1 reverse transcriptase.

Surface diffusion coefficients for room acoustics: free-field measures

A surface diffusion coefficient is needed in room acoustics to enable the quality of diffusing surfaces to be evaluated. It may also facilitate more accurate geometric room acoustic models. This paper concentrates on diffusion coefficients derived from free-field polar responses. An extensive set of two- and three-dimensional measurements and predictions was used to test the worth of different diffusion coefficient definitions. The merits and problems associated with these types of coefficients are discussed, and past parameters reviewed. Two new coefficients are described. The new measure based on the autocorrelation function is forwarded as the best free-field coefficient. The strengths and weaknesses of the coefficient are defined.

From a profiled diffuser to an optimized absorber

The quadratic residue diffuser was originally designed for enhanced scattering. Subsequently, however, it has been found that these diffusers can also be designed to produce exceptional absorption. This paper looks into the absorption mechanism of the one-dimensional quadratic residue diffuser. A theory for enhanced absorption is presented. Corresponding experiments have also been done to verify the theory. The usefulness of a resistive layer at the well openings has been verified. A numerical optimization was performed to obtain a better depth sequence. The results clearly show that by arranging the depths of the wells properly in one period, the absorption is considerably better than that of a quadratic residue diffuser.

The adaptive beam-tracing algorithm

The most popular models to predict sound propagation in architectural spaces involve the tracing of rays, images, or beams. Most current beam-tracing methods use conical or triangular beams that may produce overlaps and holes in the predicted sound field. Hence a new method has been developed whereby the shape of reflected beams is governed by the shape of reflecting surfaces so as to produce a geometrically perfect description of the sound propagation for halls with occluding surfaces. The method also facilitates the calculation of diffuse sound propagation by managing the energy transfer from a specular model to a diffuse model. This adaptive beam-tracing method compares well with other methods in terms of speed and accuracy.

Imaging membrane potential with voltage-sensitive dyes

Membrane potential can be measured optically using a variety of molecular probes. These measurements can be useful in studying function at the level of an individual cell, for determining how groups of neurons generate a behavior, and for studying the correlated behavior of populations of neurons. Examples of the three kinds of measurements are presented. The signals obtained from these measurements are generally small. Methodological considerations necessary to optimize the resulting signal-to-noise ratio are discussed.

Photoinduced dehydrogenation of defects in undoped a-si:H using positron annihilation spectroscopy

We report changes in variable-energy positron annihilation spectroscopy measurements on undoped hydrogenated amorphous silicon films after light soaking. The change, seen predominantly in the high momentum band of the annihilation radiation, is not reversed by thermal annealing. We suggest, following recent models of the Staebler-Wronski effect, that light exposure induces hydrogen trapped in vacancylike defects to become mobile in the Si network. The observations place constraints on models of hydrogen motion fitting macroscopic Staebler-Wronski effect kinetics and may help to achieve a definitive description of metastability in a-Si:H.

Odors elicit three different oscillations in the turtle olfactory bulb

We measured the spatiotemporal aspects of the odor-induced population response in the turtle olfactory bulb using a voltage-sensitive dye, RH414, and a 464-element photodiode array. In contrast with previous studies of population activity using local field potential recordings, we distinguished four signals in the response. The one called DC covered almost the entire area of the olfactory bulb; in addition, three oscillations, named rostral, middle, and caudal according to their locations, occurred over broad regions of the bulb. In a typical odor-induced response, the DC signal appeared almost immediately after the start of the stimulus, followed by the middle oscillation, the rostral oscillation, and last, the caudal oscillation. The initial frequencies of the three oscillations were 14.1, 13.0, and 6.6 Hz, respectively. When the rostral and caudal oscillations occurred together, their frequencies differed by a factor of 1.99 +/- 0.01. The following evidence suggests that the four signals are functionally independent: (1) in different animals some signals could be easily detected whereas others were undetectable; (2) the four signals had different latencies and frequencies; (3) the signals occurred in different locations and propagated in different directions; (4) the signals responded differently to changes in odor concentration; (5) the signals had different shapes; and (6) the rostral and caudal signals added in a simple, linear manner in regions where the location of the two signals overlapped. However, the finding that the frequency of the rostral oscillation is precisely two times that of the caudal oscillation suggests a significant relationship between the two. The location of the caudal oscillation in the bulb changed from cycle to cycle, implying that different groups of neurons are active in different cycles. This result is consistent with the earlier findings in the olfactory system of the locust (). Our results suggest an additional complexity of parallel processing of olfactory input by multiple functional population domains.

Clinical pharmacology of dopamine agonists

With the availability of newer dopamine agonists selective for dopamine (D2) receptor subtypes, medical management of Parkinson's disease has progressed substantially. These agents can decrease the frequency of ergot-related side effects and dyskinesias. Also, when given as adjunctive therapy with levodopa, they can allow the levodopa maintenance dosage to be reduced without loss of symptom control. Based on early clinical experience, dopamine agonists can also be prescribed as initial monotherapy and can delay therapy with levodopa. Their therapeutic roles will be defined further by long-term studies.

CYP2D6 inhibition by fluoxetine, paroxetine, sertraline, and venlafaxine in a crossover study: intraindividual variability and plasma concentration correlations

The authors report the CYP2D6 inhibitory effects of fluoxetine, paroxetine, sertraline, and venlafaxine in an open-label, multiple-dose, crossover design. Twelve CYP2D6 extensive metabolizers were phenotyped, using the dextromethorphan/dextrorphan (DM/DX) urinary ratio, before and after administration of fluoxetine 60 mg (loading dose strategy), paroxetine 20 mg, sertraline 100 mg, and venlafaxine 150 mg. Paroxetine, sertraline, and venlafaxine sequences were randomized with 2-week washouts between treatments; fluoxetine was the last antidepressant (AD) administered. Comparing within groups, baseline DM/DX ratios (0.017) were significantly lower than DM/DX ratios after treatment (DM/DXAD) with fluoxetine (0.313, p < 0.0001) and paroxetine (0.601, p < 0.0001) but not for sertraline (0.026, p = 0.066) or venlafaxine (0.023, p = 0.485). Between groups, DM/DXAD ratios were significantly higher for fluoxetine and paroxetine compared to sertraline and venlafaxine. No differences between DM/DXAD ratios were found for fluoxetine and paroxetine although more subjects phenocopied to PM status after receiving the latter (42% vs. 83%; chi 2 = 4.44, p = 0.049, df = 1). Similarly, no differences between DM/DXAD ratios were found for sertraline and venlafaxine. Of note, the DM/DXAD for 1 subject was much lower after treatment with paroxetine (0.058) compared to fluoxetine (0.490), while another subject exhibited a much lower ratio after treatment with fluoxetine (0.095) compared to paroxetine (0.397). Significant correlations between AD plasma concentration and DM/DXAD were found for paroxetine (r2 = 0.404, p = 0.026) and sertraline (r2 = 0.64, p = 0.002) but not fluoxetine or venlafaxine. In addition, DM/DXAD correlated with baseline isoenzyme activity for paroxetine, sertraline, and venlafaxine groups. These results demonstrate the potent, but variable, CYP2D6 inhibition of fluoxetine and paroxetine compared to sertraline and venlafaxine. CYP2D6 inhibition may be related, in part, to dose, plasma concentration, and baseline isoenzyme activity, and these correlations merit further investigation.

CYP2D6 status of extensive metabolizers after multiple-dose fluoxetine, fluvoxamine, paroxetine, or sertraline

The aim of this study was to evaluate the CYP2D6 inhibitory effects of four selective rerotonin re-uptake inhibitors (SSRIs). Thirty-one healthy subjects were phenotyped as extensive metabolizers using the dextromethorphan/dextrorphan (DM/DX) urinary ratio as a marker for CYP2D6 activity before and after 8 days of administration of fluoxetine 60 mg (loading dose strategy), fluvoxamine 100 mg, paroxetine 20 mg, or sertraline 100 mg in a parallel-group design. Statistical analysis was performed on log-transformed DM/DX ratios because of variability within and between treatment groups. DM/DX ratios before (DM/DX(BL)) and after (DM/DX(SSRI)) were compared within and between the four SSRI groups. DM/DX(BL) ratios were not significantly different between the four SSRI treatment groups. Comparing within groups, significant differences between DM/DX(BL) and DM/DX(SSRI) were found for the fluoxetine (p < 0.001; ratio values, 0.020 vs. 0.364) and paroxetine (p = 0.0005, ratio values 0.029 vs. 1.085) but not for the fluvoxamine or sertraline groups. Comparing between groups, significant differences in DM/DX(SSRI) ratios were found for fluoxetine versus sertraline (p = 0.0019, DM/DX = 0.364 vs. 0.057), fluoxetine versus fluvoxamine (p < 0.0001, DM/DX = 0.364 vs. 0.019), paroxetine versus sertraline (p = 0.0026, DM/DX = 1.085 vs. 0.057), and paroxetine versus fluvoxamine (p < 0.0001, DM/DX = 1.085 vs. 0.019). No significant differences were noted between the two potent CYP2D6 inhibitors, fluoxetine and paroxetine, or the two weakest inhibitors, fluvoxamine and sertraline. Five subjects in the fluoxetine and four subjects in the paroxetine groups changed to poor metabolizer phenotype (DM/DX > or = 0.3) after treatment. Although CYP2D6 inhibitory effects of fluvoxamine and sertraline did not yield significant differences from baseline, some subjects exhibited DM/DX ratio increases of 150 to 200%. One paroxetine-treated subject did not exhibit any CYP2D6 inhibition. SSRI dose and plasma concentration may be correlated with the extent of CYP2D6 inhibition and should be further investigated.

Reversible metabolism of clozapine and clozapine N-oxide in schizophrenic patients

1. To characterize the interconversion process between clozapine and its metabolite clozapine N-oxide (CNO), eight healthy male schizophrenics were administered a single dose of clozapine or CNO in a randomized crossover manner. 2. Using a general pharmacokinetic model for the interconversion process, the mean total clearances of clozapine and CNO were 28.45 L/hr and 45.30 L/hr, respectively. These values were similar to the values obtained by the usual model-independent method of pharmacokinetic analysis. 3. When administered clozapine, mean CNO plasma concentrations of 17.7 +/- 16.4 ng/ml were slightly lower than the other clozapine metabolite-desmethylclozapine (DCLOZ) plasma levels of 24.4 +/- 8.6 ng/ml at the 12 hour time point. When CNO was administered, plasma concentrations at the 12 hour time point of clozapine were twice the amount of CNO (28.1 +/- 8.9 ng/ml vs 14.4 +/- 8.8 ng/ml). 4. DCLOZ plasma concentrations were detected in all patients upon clozapine administration. Upon CNO administration, only one patient had detectable plasma DCLOZ levels. 5. The interconversion process of clozapine and CNO could partially account for the wide interpatient variability reported for clozapine plasma concentrations in schizophrenic patients.

Voltage-sensitive dyes for monitoring multineuronal activity in the intact central nervous system

Optical monitoring of activity provides new kinds of information about brain function. Two examples are discussed in this article. First, the spike activity of many individual neurons in small ganglia can be determined. Second, the spatiotemporal characteristics of coherent activity in the brain can be directly measured. This article discusses both general characteristics of optical measurements (sources of noise) as well as more methodological aspects related to voltage-sensitive dye measurements from the nervous system.

Principles of drug administration in renal insufficiency

Normal renal function is important for the excretion and metabolism of many drugs. Renal diseases which affect glomerular blood flow and filtration, tubular secretion, reabsorption and renal parenchymal mass alter drug clearances and lead to the need for alterations in dosage regimens to optimise therapeutic outcome and minimise the risk of toxicity. Renal disease is increasing and the cost of care has risen progressively over the past decade. Part of these costs is related to inappropriate drug therapy and excessive drug use. Although there are a variety of methods for evaluating the various aspects of renal function, the most practical and commonly used clinical measure of renal function is estimated creatinine clearance (CLCR) as a marker for glomerular filtration. This is useful since alterations in drug clearance are proportional to alterations in CLCR, and this relationship is used as the basis for changing doses and dosage intervals for drugs which are largely renally excreted. Two populations, neonates and the elderly, are at risk of inappropriate drug dosage due to physiological changes in renal function. Estimated CLCR may not be the best method of evaluating renal function in these patients, and dosage regimens should be carefully considered. Renal insufficiency and concurrent drug therapy used in these populations can either increase or decrease drug absorption, depending on the particular agent. Drug distribution may be altered in renal insufficiency due to pH-dependent protein binding and reduced protein (primarily albumin) levels. Interestingly, renal disease may affect hepatic as well as renal drug metabolism; the exact mechanisms for these changes are not well understood. The most important quantitative pharmacokinetic change is excretion. Glomerular filtration and tubular process may both be affected but not to the same extent, and the type of renal disease may differentially affect filtration and excretion. Drug removal by dialysis is dependent on a number of factors, including the characteristics of a particular drug and the type of dialysis and equipment used. Therapeutic outcomes may be evaluated using end-points such as plasma concentrations, patient outcomes such as reduction in fever or negative cultures, and system-wide changes such as drug-use or laboratory-use patterns.

Plasma alpha-one acid glycoprotein and haloperidol concentrations in schizophrenic patients

Thirty six schizophrenic patients were randomly assigned to placebo or haloperidol treatment for 6 weeks. Blood samples to measure plasma alpha-one acid glycoprotein (AAG), haloperidol and reduced haloperidol concentrations were obtained at baseline and weeks 2, 4, and 6. Blood samples were obtained 10-12 h after the evening dose and prior to the morning dose. Haloperidol and reduced haloperidol was assayed by HPLC with electrochemical detection. Plasma AAG levels were assayed by radial immunodiffusion. Patients were clinically assessed by the Brief Psychiatric Rating Scale (BPRS) and Abnormal Involuntary Movement Scale at baseline and weeks 2, 4, and 6. BPRS scores did not significantly decrease during placebo treatment, although a slight drop in plasma AAG levels was found. Haloperidol produced a significant decrease in BPRS scores and plasma AAG levels. Mean plasma haloperidol levels were 12.9 +/- 14.7 ng/ml at week 6. Significant correlations between decreasing BPRS scores and plasma AAG levels were not found with only a strong trend at week 2 (r = 0.445, p = 0.073). The role of AAG and psychotropic drug disposition in psychiatric patients requires further evaluation.

Lack of pharmacokinetic interaction between buspirone and haloperidol in patients with schizophrenia

The pharmacokinetic interaction between buspirone and haloperidol was evaluated in schizophrenic patients in two different groups. In both groups, haloperidol doses (10-40 mg/day) remained constant for 6 weeks before the addition of buspirone 10 mg three times daily. Serial blood samples were obtained from the 11 patients in group I at baseline (before addition of buspirone) and after administration for 24 hours. The pharmacokinetic parameters of haloperidol were determined alone and with coadministration of buspirone. In group II, buspirone 10 mg three times daily was added to treatment with haloperidol in 27 patients. Blood samples were obtained before addition of buspirone and at weeks 2 and 6 of treatment with buspirone. Samples were obtained 10 to 12 hours after administration of the evening dose and before the morning dose. Haloperidol and its metabolite, reduced haloperidol (RH), were assayed by means of high-performance liquid chromatography with electrochemical detection. Significant changes in the pharmacokinetic parameters of haloperidol were not found in group I; a mean increase in the half-life (t1/2) of haloperidol from 21.5 to 28.1 hours was observed, but this finding was not statistically significant. Under steady-state conditions, plasma levels of haloperidol in the patients in group II did not change significantly from baseline to week 6. Plasma concentrations of RH remained unaltered in both groups. The results indicate that coadministration of buspirone does not markedly affect the pharmacokinetics or plasma concentrations of haloperidol.

Conditioned enhancement of the early component of the rat eyeblink reflex

Conditioned enhancement of the rat eyeblink reflex was studied using as a response measure the electromyogram (EMG) in the orbicularis oculi (oo) muscle, which is responsible for the active force generating eyelid closure. During a reflex eyeblink, the EMG evidences both a short-latency (R1) and a long-latency (R2) component, mediated by different circuits. The R2 response exhibits several experience- or use-dependent modifications. We were interested in the modifiability of the neurophysiologically simpler R1 response. Experiments were designed to determine whether the R1 response can be enhanced by a conditioned stimulus (CS) that has been explicitly paired with an aversive unconditioned stimulus (US). The R1 response was elicited by electrical stimulation of the supraorbital branch of the trigeminal nerve. Following long-delay conditioning, the CS produced a significant R1 enhancement and latency decrease that were dependent upon explicit CS-US pairings. The CS by itself produced no significant EMG response, consistent with a modulatory rather than additive effect. This is the first demonstration that the R1 response can be associatively modulated. Based on other evidence, we hypothesize that the CS-produced enhancement results from a relatively direct projection from the amygdala to the R1 circuit. As an index of aversive conditioning, R1 enhancement may prove to be a useful expression system because it offers high temporal resolution and the underlying circuitry is relatively simple-the shortest path from the fifth nerve to the muscle consisting of only two central synapses.

Disposition of remoxipride in Chinese schizophrenic patients

The disposition of remoxipride was evaluated in 13 male chronic schizophrenic patients. A single 150 mg dose of remoxipride was administered and blood sampling performed over the following 48 hours. The mean (SD) oral clearance and half-life of remoxipride were 74.46 (25.9) ml/min and 5.46 (0.87) hours, respectively. The mean (SD) AUC for remoxipride was 25,320 (9,820) ng.h/ml. A wide interpatient variability was observed. Compared to Caucasian studies there were no significant differences in the disposition of remoxipride.

Serotonin selective reuptake inhibitor drug interactions and the cytochrome P450 system

The article focuses on the effects of the serotonin selective reuptake inhibitors (SSRIs) on specific drug metabolizing isoenzymes: CYP2D6, CYP3A3/4, CYP1A2, CYP2C9, and CYP2C19. Both in vitro and in vivo data regarding the inhibition potential of the SSRIs at each of these isoenzyme systems are reviewed. In general, the magnitude of the in vivo interactions between the SSRIs and substrates for these isoenzyme systems mirrors to a large extent their in vitro inhibitory potencies. However, in vitro work is limited owing to pharmacokinetic considerations, the effect of metabolites on the isoenzymes, and the likelihood that several isoenzymes are co-responsible for the metabolism of a substrate.

Cell type- and differentiation stage-dependent expression of PML domains in rat, detected by monoclonal antibody HIS55

Using mouse monoclonal antibody (mAb) HIS55, we identified a nuclear antigen (ag) that exhibited a staining pattern of discrete foci. Such foci could be detected in cells of many mammalian species. These nuclear foci were not associated with nuclear membrane, nucleoli, or mitotic chromosomes. In isolated rat liver nuclei, HeLa cells, and normal human and rat lymph nodes, staining of HIS55 colocalized with that of 5E10. 5E10 recognizes PML nuclear domains, multimolecular complexes of unknown function containing the product of PML gene and at least two other components. HIS55 foci were expressed widely in many tissues but the expression level varied in a cell type-specific manner, with the number of HIS55 nuclear foci ranging from 0 (as in neurons) to over 100 (as in megakaryocytes) and the size ranging from fine (as in cortical thymocytes) to very large (as in urethra epithelium). HIS55 ag expression level also varied among cells of the same lineage, as observed in embryonic development of rat and in the hemopoietic system of adult rat. The expression level of HIS55 foci roughly correlated with the overall rate of protein synthesis of cells, supporting a role of PML domains as transcription regulatory units. The expression of HIS55 foci, however, did not correlate with the growth index of cell populations. Our observations on normal tissues agreed with the hypothesis that PML domain expression is regulated by external, possibly site-dependent factors. We further supported this by demonstrating that PML domains in rat ventral prostate epithelia were upregulated upon castration.

Roxithromycin disposition in patients on continuous ambulatory peritoneal dialysis

Roxithromycin is a macrolide antibiotic with a spectrum of activity similar to erythromycin. Roxithromycin has been shown to have a favourable pharmacokinetic profile with more reliable absorption and higher, prolonged plasma and tissue concentrations compared with erythromycin. The pharmacokinetics and dialysis clearance of roxithromycin were studied in twelve patients with end-stage renal disease on continuous ambulatory perionteal dialysis. Following a single 300 mg oral dose, multiple blood, dialysate and urine samples were collected over 48 h and assayed for roxithromycin by a microbiological method. Peak plasma concentrations were attained between 0.5 and 5 h, and ranged from 2.3 to 6.8 mg/L. The mean elimination half-life was 20.6 +/- 8.7 h, compared with 10 to 14 h previously reported in healthy volunteers given a single 300 mg dose. Plasma clearance relative to bioavailability (Clp/F) ranged from 37.3 to 118.3 mL/min. The percentage of the dose recovered in the dialysate and net dialysis clearance were low, ranging from 1.0 to 3.1% and 0.9 to 1.8 mL/min, respectively. Only 1% of the dose was recovered in the urine. These results demonstrate that roxithromycin is not substantially removed by continuous ambulatory peritoneal dialysis, and its elimination is prolonged in renal failure, possibly due to impaired nonrenal elimination.

Disposition and covalent binding of ibuprofen and its acyl glucuronide in the elderly

Ibuprofen is an over-the-counter nonsteroidal anti-inflammatory drug with a low incidence of severe adverse reactions. It is metabolized by oxidation to carboxyibuprofen and hydroxyibuprofen and by conjugation to an acyl glucuronide. In vitro studies have indicated that ibuprofen glucuronide is labile and reactive, forming covalent adducts with proteins. To verify the formation of ibuprofen-protein adducts in vivo, the pharmacokinetics of ibuprofen glucuronide and its covalent binding to plasma proteins were studied in five elderly patients who received long-term administration of oral doses of ibuprofen. Plasma levels of ibuprofen glucuronide were low relative to those of ibuprofen; the ratio of area under the plasma concentration versus time curve for the glucuronide relative to the parent drug was only 4%. Covalent binding of ibuprofen to plasma protein was observed in all patients, correlating well with the area under the plasma concentration versus time curve of ibuprofen glucuronide (r = 0.966). Compared with reports for other nonsteroidal anti-inflammatory drugs that form acyl glucuronides, plasma levels of ibuprofen-protein adduct are low during long-term administration. The observed lower reactivity in vivo is probably attributable to the greater stability of ibuprofen glucuronide relative to other acyl glucuronides.

Intra- and interethnic variability in reduced haloperidol to haloperidol ratios

Steady-state haloperidol and reduced haloperidol concentrations were measured in 250 schizophrenic patients from 4 ethnic groups: 39 Blacks, 66 Caucasians, 82 Chinese, and 63 Mexican Americans. The distribution of the reduced haloperidol to haloperidol concentration (RH/HL) ratios was bimodal in all ethnic groups, with the antimode determined by probit plot as 0.46, 0.51, 0.36, and 0.76, respectively. With these antimodes, the proportion of patients with low RH/HL ratios were 41%, 42%, 73%, and 57% in the four ethnic groups, respectively. Compared with the other three ethnic groups, in the Chinese patients the ratio was lower. The mean RH/HL ratio in the Chinese was 0.34 compared with 0.81 to 0.87 in the non-Chinese groups. In 53 patients who were treated with two or more haloperidol dosage regimens, steady-state haloperidol and reduced haloperidol drug concentrations obtained from the different regimens were positively correlated with the haloperidol dose (R = .79 and R = .62, respectively). Our data suggest not only the existence of a bimodal distribution in the RH/HL ratio, but also that the antimode separating the low and high ratio subgroups is different among the various ethnic groups.

Antidepressant drug interactions and the cytochrome P450 system. The role of cytochrome P450 2D6

The selective serotonin reuptake inhibitors (SSRIs) and venlafaxine display the following rank order of in vitro potency against the cytochrome P450 (CYP) isoenzyme CYP2D6 as measured by their inhibition sparteine and/or dextromethorphan metabolism: paroxetine > fluoxetine identical to norfluoxetine > or = sertraline > or = fluvoxamine > venlafaxine. On this basis, paroxetine would appear to have the greatest and fluvoxamine and venlafaxine the least potential for drug interactions with CYP2D6-dependent drugs. In vivo, inhibitory potency is affected by the plasma concentration of the free (unbound) drug, a potentially important consideration since many CYP2D6-metabolised drugs exhibit nonlinear (saturable) kinetics, and by the presence of metabolites, which might accumulate and interact with the CYP system. Under steady-state conditions, paroxetine and fluoxetine are approximately clinically equipotent inhibitors of CYP2D6 in vivo (as determined through their effects on desipramine metabolism); sertraline, in contrast, shows lower steady-state plasma concentrations than fluoxetine and, hence, a less pronounced inhibition of CYP2D6. Of the drugs that are metabolised by CYP2D6, secondary amine tricyclic antidepressants, antipsychotics (e.g. phenothiazines, and risperidone), codeine, some antiarrhythmics (e.g. flecainide) and beta-blockers form the focus of clinical attention with regard to their potential interactions with the SSRIs. Coadministration of desipramine and fluoxetine (20 mg/day) at steady-state produced an approximately 4-fold elevation in peak plasma desipramine concentrations, while the long half-life of the active metabolite norfluoxetine was responsible for a significant and long lasting (approximately 3 weeks) elevation of plasma desipramine concentrations after discontinuation of fluoxetine. Similarly, coadministration of desipramine with paroxetine produced an approximately 3-fold increase in plasma desipramine concentration. In contrast, coadministration of desipramine and sertraline (50 mg/day) for 4 weeks resulted in a considerably more modest (approximately 30%) elevation in plasma desipramine concentrations. Coadministration of fluoxetine (60 mg/day, as a loading dose) [equivalent to serum concentrations obtained with 20 mg/day at steady-state] with imipramine or desipramine resulted in approximately 3- to 4-fold increases in plasma area under the curve (AUC) values for both imipramine and desipramine (illustrating a significant drug interaction potential at multiple isoenzymes). Consistent with its minimal in vitro effect on CYP2D6, fluvoxamine shows minimal in vivo pharmacokinetic interaction with desipramine, but does interact with imipramine (approximately 3- to 4-fold increase in AUC) through inhibition of CYP3A3/4, CYP1A2, and CYP2C19. Thus, the extent of the in vivo interaction between the SSRIs and tricyclic antidepressants mirrors to a large extent their in vitro inhibitory potencies against CYP2D6 and other isoenzyme systems, especially if one takes into account pharmacokinetic factors.

Rapid formation of clozapine in guinea-pigs and man following clozapine-N-oxide administration

Clozapine and its metabolite clozapine-N-oxide (0.5 mg/kg) were administered intraperitoneally to guinea-pigs. Significant amounts of clozapine were detected in plasma, liver, frontal cortex and caudate after clozapine-N-oxide administration. The amount of clozapine detected in plasma two hours post-administration of N-oxide was approximately 40% of the amount of clozapine after clozapine injection. Tissue concentrations of clozapine in liver, frontal cortex and caudate were greater than plasma concentrations. Clozapine concentrations were almost equivalent in the liver. Clozapine concentrations after N-oxide injection were approximately 40-50% lower compared to clozapine concentrations after clozapine administration in the frontal cortex and caudate. A single dose of clozapine-N-oxide was given to a schizophrenic patient. Clozapine plasma concentrations were detected after N-oxide administration. This study shows that clozapine is formed from its N-oxide metabolite and that a reversible metabolic pathway exists for clozapine and clozapine-N-oxide.

Disposition of clozapine and desmethylclozapine in schizophrenic patients

The disposition of the atypical clozapine and its desmethyl metabolite were evaluated in fourteen male chronic patients. A single 100 mg dose of clozapine was administered and blood sampling performed over the following 72 hours. The mean (SD) oral clearance and half-life of clozapine were 55.4 (29.7) L/hr and 13.7 (9.9) hours, respectively. The mean (SD) AUC for clozapine and desmethylclozapine was 2389.9 (1406) and 751.1 (622.9) ng.hr/mL, respectively. The elimination of the metabolite is rate limited by its formation from cloza-pine. A wide interpatient variability in clozapine and desmethylclozapine pharmacokinetics was observed.

Latent inhibition of the rat eyeblink response: effect of hippocampal aspiration lesions

The effect of hippocampal aspiration lesions on latent inhibition of eyeblink conditioning in the restrained rat preparation was examined. Rats received either sham, cortical control, or hippocampal aspiration lesions. Control animals, but not animals with hippocampal lesions, showed slower conditioning after being preexposed to the conditioned stimulus (latent inhibition). Together with previous results regarding the effect of hippocampal lesions in acquisition and extinction of delay conditioning, the present study suggests that the restrained rat preparation may serve as a reliable way of investigating hippocampal participation in different classical conditioning paradigms.

Hypoxia, arterial pH and theophylline disposition

Theophylline is a bronchodilator used extensively in the management of obstructive pulmonary disease. Factors implicated in altered theophylline clearance include smoking, age, concomitant drug intake, liver disease and left ventricular heart failure. However, evidence now suggests that theophylline clearance may be altered by changes in severity of the pulmonary obstruction, hypoxia and variation in arterial pH. The in vitro disposition of theophylline has been evaluated in isolated rat livers and mouse hepatocytes. In vivo studies have assessed the metabolism of theophylline under hypoxia in rats, rabbits and dogs. In isolated mouse hepatocytes and rat livers, low oxygen concentrations resulted in higher theophylline concentrations, a longer elimination half-life and a decrease in the production of the metabolite 1,3-dimethyl uric acid, suggesting impaired metabolism of theophylline. In rabbits, hypoxia, hypercapnia and respiratory acidosis decreased total body clearance and increased plasma theophylline concentrations. On the other hand, experiments involving dogs showed no significant changes in theophylline concentrations or pharmacokinetic parameters with hypoxia. At present, animal studies remain inconclusive. This can be attributed to the use of different animal models and variations in study methodology, including the extent and duration of hypoxia and acidaemia, concurrent acid-base disorders such as hypercapnia, as well as the severity of pulmonary obstruction. Human studies assessing alterations in theophylline disposition secondary to the hypoxia present in pulmonary disease are few and include mostly case reports and observational studies. There is evidence suggesting decreased theophylline clearance and protein binding during acute illness and some consensus can be achieved using case reports and controlled studies. There is additional evidence that drug clearance decreases with age and that elderly patients may have a decreased theophylline clearance at baseline. However, the most obvious markers appear to be the severity of pulmonary disease and the rate of change in the patient's condition. Caution should be exercised when administering theophylline to elderly patients with chronic obstructive pulmonary disease presenting with acute exacerbations of a concomitant respiratory illness, as these patients appear to be most likely to exhibit altered theophylline metabolism. Therefore, they would be at increased risk for toxicity should conventional dosages be used during an acute respiratory event.

High-performance liquid chromatography determination of dextromethorphan and dextrorphan for oxidation phenotyping by fluorescence and ultraviolet detection

To establish the usefulness of fluorescence detection to quantify urinary concentrations of dextromethorphan and dextrorphan for oxidation phenotyping, we determined the molar concentration ratio of dextromethorphan to dextrorphan in 38 subjects by UV and fluorescence detection. Dextromethorphan and dextrorphan concentrations were quantified after overnight hydrolysis of urine samples and organic solvent extraction with heptane and butanol. The compounds were separated by high-performance liquid chromatography using a phenyl column and a mobile phase consisting of acetonitrile and an aqueous mixture of 0.01 M heptane sulfonic acid and 0.01 M phosphate buffer. The eluents were detected in series by a UV detector (280 nm) and fluorescence detector (excitation 280 nm and emission 310 nm). The dextromethorphan to dextrorphan molar concentration ratio by UV and fluorescence detection was highly correlated (r = 0.997) and not statistically different (p = 0.1036). However, increased sensitivity with fluorescence detection enabled detection of lower dextromethorphan and dextrorphan concentrations when compared with UV detection. Fluorescence detection was able to detect dextromethorphan as low as 0.02 microgram/ml, which may be helpful in phenotyping individuals with extremely rapid metabolism of dextromethorphan. Fluorescence detection also produced chromatograms with significantly less interference and allows a more accurate quantitation of dextromethorphan and dextrorphan concentrations.

Prolonged haloperidol and reduced haloperidol plasma concentrations after decanoate withdrawal

Haloperidol and reduced haloperidol plasma concentrations were measured in twelve schizophrenic patients upon cessation of haloperidol decanoate (HLD) treatment. Each patient received HLD 100 mg every 4 weeks for five injections. After the fifth injection, HLD was discontinued. Haloperidol and reduced haloperidol plasma concentrations were obtained prior to cessation and at weeks 1, 3, 4, 5, 7, 9, 11, and 13 post-injection. Haloperidol and reduced haloperidol plasma concentrations were assayed by HPLC. Both haloperidol and reduced haloperidol plasma concentrations were detectable 13 weeks post HLD discontinuation. Maximal haloperidol plasma concentrations were observed at one week post cessation and gradually declined. The mean elimination half-life for haloperidol was 27.4 +/- 8.6 days (range 19.0-47.0 days). Reduced haloperidol plasma concentrations declined very slowly. Our results show that both haloperidol and reduced haloperidol plasma concentrations can remain for extended time periods after HLD is discontinued.