Coffee inhibition of CYP3A4 in vitro was not translated to a grapefruit-like pharmacokinetic interaction clinically.

Grapefruit can augment oral medication bioavailability through irreversible (mechanism-based) inhibition of intestinal CYP3A4. Supplementary data from our recent coffee-drug interaction clinical study showed some subjects had higher area under the plasma drug concentration - time curve (AUC) and plasma peak drug concentration (Cmax) of the CYP3A4 probe felodipine compared to aqueous control. It was hypothesized that coffee might interact like grapefruit in responsive individuals. Beans from six geographical locations were consistently brewed into coffee that was separated chromatographically to a methanolic fraction for in vitro inhibition testing of CYP3A4 metabolism of felodipine at 1% coffee strength. The effect of simultaneous incubation and 10-min preincubation with coffee fractions determined whether coffee had direct and mechanism-based inhibitory activity. A subsequent five-way randomized balanced controlled crossover clinical study evaluated the clinical pharmacokinetic interaction with single-dose felodipine. Grapefruit juice, water, or three of the in vitro tested coffees were ingested at 300 mL alone 1 h before and then with felodipine. In vitro, all six coffees decreased felodipine metabolism for both simultaneous and preincubation exposure compared to corresponding control. Five coffees demonstrated mechanism-based inhibition. Grapefruit increased felodipine AUC0-8 (25 vs. 13 ng.h/mL, P < 0.001) and Cmax (5.8 vs. 2.7 ng/mL, P < 0.001) and decreased dehydrofelodipine/felodipine AUC0-8 ratio (0.84 vs. 1.29, P < 0.001), while the three coffees caused no change in these parameters compared to water. Despite high in vitro potency of CYP3A4 inhibition, the coffees did not cause a clinical pharmacokinetic interaction possibly from insufficient amount of inhibitor(s) in coffee reaching intestinal CYP3A4 during the absorption phase of felodipine. The results of this study highlight the need for follow-up clinical testing when in vitro results indicate the possibility of an interaction.

Coffee-Antihypertensive Drug Interaction: A Hemodynamic and Pharmacokinetic Study With Felodipine.

OBJECTIVES: A period of abstinence from coffee to permit caffeine elimination appears to enable increased blood pressure on subsequent exposure. We hypothesized that this would offset the antihypertensive effect of the dihydropyridine calcium channel blocker felodipine. METHODS: A randomized, single-dose, crossover study assessed hemodynamic and pharmacokinetic effects following 2 days without coffee and caffeine-containing foods. Consistently brewed black coffee (2×300ml), felodipine maximum recommended dose (10mg), and coffee plus felodipine were tested in middle-aged normotensive subjects. RESULTS: Pretreatment plasma caffeine concentrations were unquantifiable. After coffee, blood pressure changes (mm Hg) averaged over study hours 1-4 were increased for brachial systolic (7.6, P < 0.001) and diastolic (4.9, P < 0.001) and aortic systolic (7.4, P < 0.001), pulse (3.0, P < 0.05) and augmentation (1.4, P < 0.05) relative to baseline. After coffee plus felodipine, they were higher for brachial systolic (4.0, P < 0.05) and diastolic (3.9, P < 0.001) and aortic systolic (4.6, P < 0.05) compared to felodipine alone. The pressor effects of coffee and its modulation by felodipine were variable among individuals. Coffee containing caffeine (127mg) caused maximum pressor effect. Caffeine and felodipine pharmacokinetics were similar for coffee and felodipine given alone or in combination indicating an interaction having a pharmacodynamic basis. Plasma felodipine concentration-diastolic blood pressure reduction relationship shifted with coffee such that doubling the felodipine concentration would eliminate the pressor effect. However, this may increase the risk of adverse drug events particularly during the timeframe without coffee. CONCLUSION: Intermittent coffee ingestion might complicate hypertension diagnosis and management for many individuals.

Optogenetic apoptosis: light-triggered cell death.

An optogenetic Bax has been designed that facilitates light-induced apoptosis. We demonstrate that mitochondrial recruitment of a genetically encoded light-responsive Bax results in the release of mitochondrial proteins, downstream caspase-3 cleavage, changes in cellular morphology, and ultimately cell death. Mutagenesis of a key phosphorylatable residue or modification of the C-terminus mitigates background (dark) levels of apoptosis that result from Bax overexpression. The mechanism of optogenetic Bax-mediated apoptosis was explored using a series of small molecules known to interfere with various steps in programmed cell death. Optogenetic Bax appears to form a mitochondrial apoptosis-induced channel analogous to that of endogenous Bax.

Enzymatic and non-enzymatic mechanisms of dimesna metabolism.

The chemical reduction of the disulfide homodimer dimesna to its constituent mesna moieties is essential for its mitigation of nephrotoxicity associated with cisplatin and ifosfamide anticancer therapies and enhancement of dialytic clearance of the cardiovascular risk factor homocysteine. The objective of this study was to investigate potential enzymatic and non-enzymatic mechanisms of intracellular dimesna reduction. Similar to endogenous intracellular disulfides, dimesna undergoes thiol-disulfide exchange with thiolate anion-forming sulfhydryl groups via the two-step SN2 reaction. Determination of equilibrium constants of dimesna reduction when mixed with cysteine or glutathione provided a mechanistic explanation for dramatic cysteine and homocysteine depletion, but sparing of the endogenous antioxidant glutathione, previously observed during mesna therapy. Dimesna was reduced by recombinant enzymes of the thioredoxin system; however, oxidation of NADPH by the glutaredoxin system was only observed in the presence of combined dimesna and reduced glutathione, suggesting formation of oxidized glutathione following an initial non-enzymatic reduction of dimesna. Production of mesna by enzymatic and non-enzymatic mechanisms in HeLa cell lysate following dimesna incubation was demonstrated by a loss in mesna production following protein denaturation and prediction of residual non-enzymatic mesna production by mathematical modeling of thiol-disulfide exchange reactions. Reaction modeling also revealed that mixed disulfides make up a significant proportion of intracellular thiols, supporting their role in providing additional nephroprotection, independent of direct platinum conjugation.

Hepatic organic anion transporting polypeptide transporter and thyroid hormone receptor interplay determines cholesterol and glucose homeostasis.

UNLABELLED: The role of organic anion transporting polypeptides (OATPs), particularly the members of OATP1B subfamily, in hepatocellular handling of endogenous and exogenous compounds is an important and emerging area of research. Using a mouse model lacking Slco1b2, the murine ortholog of the OATP1B subfamily, we have demonstrated previously that genetic ablation causes reduced hepatic clearance capacity for substrates. In this study, we focused on the physiological function of the hepatic OATP1B transporters. First, we studied the influence of the Oatp1b2 deletion on bile acid (BA) metabolism, showing that lack of the transporter results in a significantly reduced expression of Cyp7a1, the key enzyme of BA synthesis, resulting in elevated cholesterol levels after high dietary fat challenge. Furthermore, Slco1b2-/- mice exhibited delayed clearance after oral glucose challenge resulting from reduced hepatic glucose uptake. In addition to increased hepatic glycogen content, Slco1b2-/- mice exhibited reduced glucose output after pyruvate challenge. This is in accordance with reduced hepatic expression of phosphoenolpyruvate carboxykinase (PEPCK) in knockout mice. We show that this phenotype is due to the loss of liver-specific Oatp1b2-mediated hepatocellular thyroid hormone entry, which then leads to reduced transcriptional activation of target genes of hepatic thyroid hormone receptor (TR), including Cyp7a1 and Pepck but also Dio1 and Glut2. Importantly, we assessed human relevance using a cohort of archived human livers in which OATP1B1 expression was noted to be highly associated with TR target genes, especially for glucose facilitating transporter 2 (GLUT2). Furthermore, GLUT2 expression was significantly decreased in livers harboring a common genetic polymorphism in SLCO1B1. CONCLUSION: Our findings reveal that OATP1B-mediated hepatic thyroid hormone entry is a key determinant of cholesterol and glucose homeostasis.

Compensatory upregulation of the adenosine system following phenylephrine-induced hypertrophy in cultured rat ventricular myocytes.

Adenosine has been shown to exert direct antihypertrophic effects on the heart, and plasma adenosine levels have been shown to be elevated in patients with heart failure. It has therefore been proposed that endogenously synthesized adenosine may function as a cardiac antihypertrophic factor. The present study was aimed to determine whether the adenosine system is altered in a potential adaptive manner following phenylephrine-induced hypertrophy in cultured neonatal rat ventricular myocytes. Phenylephrine produced significant hypertrophy as determined by cell size and atrial natriuretic peptide gene expression, which was accompanied by significantly increased gene and protein expression of adenosine A(1), A(2a), and A(3) receptors. These effects and the hypertrophic response were prevented by the alpha(1)-adrenoceptor antagonist prazosin as well as pharmacological agonists for all adenosine receptor subtypes. The upregulation of adenosine receptors by phenylephrine was also abrogated by adenosine 5'-(alpha,beta-methylene)diphosphate, an inhibitor of ectosolic 5'-nucleotidase. Moreover, phenylephrine significantly increased production of adenosine from myocytes in the presence of a nucleoside transport and adenosine deaminase inhibitor, the combination of which abrogated the hypertrophic effect of phenylephrine. The latter effect was reversed by adenosine receptor antagonists. Phenylephrine also produced a significant upregulation in expression levels of equilibrative nucleoside transporter 1 although expression levels of equilibrative nucleoside transporter 2 were unaffected. Taken together, our results suggest an adaptive upregulation of the adenosine system to phenylephrine-induced cardiomyocyte hypertrophy that serves to limit the hypertrophic effect of alpha(1-)adrenoceptor activation.

Mesna for the treatment of hyperhomocysteinemia in hemodialysis patients.

BACKGROUND: Increased plasma total homocysteine (tHcy) is a risk factor for the development of atherosclerosis and thrombosis present in over 90% of patients with end-stage renal disease (ESRD). We hypothesized that 12 mg/kg intravenous mesna administered predialysis would cause a significant decrease in plasma tHcy compared to placebo. METHODS: Patients with ESRD were recruited for 1- and 4-week placebo-controlled, cross-over studies. Intravenous 12 mg/kg mesna or placebo was administered 3 times weekly predialysis. RESULTS: One week of 12 mg/kg intravenous mesna significantly decreased predialysis plasma tHcy by 12.8 +/- 7.8% (placebo 23.4 +/- 8.0 micromol/l vs. mesna 20.5 +/- 7.6 micromol/l, p = 0.0044). Four weeks of treatment yielded no significant decline in predialysis plasma tHcy (placebo 18.3 +/- 8.5 micromol/l vs. mesna 18.7 +/- 6.3 micromol/l, p = 0.41). CONCLUSIONS: Although 12 mg/kg mesna significantly enhances tHcy excretion, prolonged treatment causes no change in plasma tHcy.

Timolol concentrations in breast milk of a woman treated for glaucoma: calculation of neonatal exposure.

A 32-year-old lactating woman with open-angle glaucoma used timolol maleate 0.5% eye drops twice daily to her right eye for 6 months. Four milk samples were collected over a span of 6 days. Timolol maleate milk levels were examined by liquid chromatography tandem mass spectrometry and found to be at a mean of 0.12 ng/mL (range, 0 to 0.37 ng/mL). At this level, the theoretical maximum relative infant dose expressed as a percentage of the weight-adjusted maternal dose was 0.012%. As most glaucoma patients administer drops to both eyes, the dosage was duplicated to reflect the more pertinent calculated theoretical relative infant dose of 0.024%. This dose of timolol is unlikely to cause systemic side effects to the healthy breastfed infant.

Mesna for treatment of hyperhomocysteinemia in hemodialysis patients: a placebo-controlled, double-blind, randomized trial.

BACKGROUND AND OBJECTIVES: Increased plasma total homocysteine is a graded, independent risk factor for the development of atherosclerosis and thrombosis. More than 90% of patients with end-stage renal disease have hyperhomocysteinemia despite vitamin supplementation. It was shown in previous studies that a single intravenous dose of mesna 5 mg/kg caused a drop in plasma total homocysteine that was significantly lower than predialysis levels 2 d after dosing. It was hypothesized 5 mg/kg intravenous mesna administered thrice weekly, before dialysis, for 8 wk would cause a significant decrease in plasma total homocysteine compared with placebo. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients with end-stage renal disease were randomly assigned to receive either intravenous mesna 5 mg/kg or placebo thrice weekly before dialysis. Predialysis plasma total homocysteine concentrations at weeks 4 and 8 were compared between groups by paired t test. RESULTS: Mean total homocysteine at 8 wk in the placebo group was 24.9 micromol/L compared with 24.3 micromol/L in the mesna group (n = 22 [11 pairs]; mean difference 0.63). Interim analysis at 4 wk also showed no significant difference between mesna and placebo (n = 32 [16 pairs]; placebo 26.3 micromol/L, mesna 24.5 micromol/L; mean difference 1.88). Multivariable adjustments for baseline characteristics did not alter the analysis. Plasma mesna seemed to reach steady-state concentrations by 4 wk. CONCLUSIONS: It is concluded that 5 mg/kg mesna does not lower plasma total homocysteine in hemodialysis patients and that larger dosages may be required.

Mesna as a nonvitamin intervention to lower plasma total homocysteine concentration: implications for assessment of the homocysteine theory of atherosclerosis.

Elevated plasma total homocysteine is independently associated with atherosclerosis. Recent randomized trials show that vitamins lower total homocysteine but do not prevent cardiovascular events, suggesting the need for nonvitamin therapies to evaluate whether a causative relationship exists. Mesna (sodium 2-mercaptoethanesulfonate) is a thiol-containing drug capable of liberating homocysteine bound by disulfide bonds to proteins, facilitating its excretion. The effect of oral mesna on total homocysteine has not been evaluated and was the objective of this study. Eleven healthy volunteers received vehicle or 10 mg/kg mesna in random order, after which serial blood and urine samples were collected over 4 hours. Plasma total homocysteine decreased by 24.2% (P < .0001) following mesna. Urinary homocysteine excretion was significantly greater with mesna (3.9 +/- 2.4 mumol) compared to vehicle (0.4 +/- 0.1 mumol), P < .01. Oral mesna decreases plasma total homocysteine and is a potential nonvitamin treatment for assessing the homocysteine theory of atherosclerosis.

The effect of mesna on plasma total homocysteine concentration in hemodialysis patients.

BACKGROUND: Plasma total homocysteine (tHcy) level is an independent risk factor for the development of atherosclerosis. The degree of risk in most of the population is decreased by using dietary vitamin supplementation; however, more than 90% of patients with end-stage renal disease have increased tHcy levels despite supplementation. Only a small fraction of tHcy is removed by hemodialysis because of extensive disulfide bonding to albumin. The objective of this study is to determine whether a single intravenous dose of mesna, a thiol-containing drug analogue of taurine, facilitates tHcy clearance during hemodialysis. METHODS: Initial in vitro thiol exchange tests were performed with mesna in plasma from dialysis patients. Mesna, 300 micromol/L (49.2 mg/L), was incubated with plasma at 37 degrees C, and free homocysteine was measured at various times. In vivo, mesna activity was tested in 10 hemodialysis patients by administering 2.5 or 5.0 mg/kg of mesna intravenously at the beginning of a treatment cycle. Blood samples were drawn throughout dialysis, and plasma tHcy levels were compared with those obtained from a previous dialysis session in which mesna was not administered. RESULTS: In vitro, mesna liberated 36.5% +/- 2.5% of protein-bound homocysteine in 30 minutes. In vivo, a single 2.5-mg/kg dose of mesna was ineffective; however, at 5.0 mg/kg, it caused a 55.2% +/- 3.9% decrease in plasma tHcy levels postdialysis compared with a 34.2% +/- 5.3% decrease with dialysis alone (P < 0.001). CONCLUSION: Intravenous mesna causes a rapid decrease in plasma tHcy levels during hemodialysis.

In vivo inhibition of growth of human tumor lines by flavonoid fractions from cranberry extract.

Edible fruits and berries may serve as sources for novel anticancer agents, given that extracts of these foods have demonstrated cytotoxic activity against tumor cell lines. Semipurified, flavonoid-rich extracts of cranberry (Vaccinia macrocarpa) were shown previously to arrest proliferation of tumor cells and induce apoptosis. However, the ability of cranberry flavonoids to inhibit tumor growth in vivo has not been reported other than in a preliminary report. As model systems for testing this activity, human tumor cell lines representative of three malignancies were chosen: glioblastoma multiforme (U87), colon carcinoma (HT-29), and androgen-independent prostate carcinoma (DU145). A flavonoid-rich fraction 6 (Fr6) and a more purified proanthocyanidin (PAC)-rich fraction were isolated from cranberry presscake and whole cranberry, respectively, by column chromatography. Fr6 and PAC each significantly slowed the growth of explant tumors of U87 in vivo, and PAC inhibited growth of HT-29 and DU145 explants (P < 0.05), inducing complete regression of two DU145 tumor explants. Flow cytometric analyses of in vitro-treated U87 cells indicated that Fr6 and PAC could arrest cells in G1 phase of the cell cycle (P < 0.05) and also induce cell death within 24 to 48 h of exposure (P < 0.05). These results indicate the presence of a potential anticancer constituent in the flavonoid-containing fractions from cranberry extracts.

Reinstalling antitumor immunity by inhibiting tumor-derived immunosuppressive molecule IDO through RNA interference.

Tumor-derived immune suppression is a major impediment to successful immune/gene cancer therapy. In the present study, we describe a novel strategy to disrupt tumor-derived immune suppression by silencing a tolerogenic molecule of tumor origin, IDO, using small interfering RNA (siRNA). Silencing of IDO in B16F10 cells in vitro using IDO-siRNA prevented catabolism of tryptophan and inhibited apoptosis of T cells. IDO-siRNA treatment of B16F10 cells in vitro inhibited subsequent growth, tumor formation, and the size of tumor formed, by those cells when transplanted into host mice. In vivo treatment of B16F10 tumor-bearing mice successfully postponed tumor formation time and significantly decreased tumor size. Furthermore, in vivo IDO-siRNA treatment resulted in recovery of T cells responses and enhancement of tumor-specific killing. Thus, silencing IDO may break tumor-derived immune suppression. These data indicate that RNA interference has potential to enhance cancer therapy by reinstalling anticancer immunity.

Thiol exchange: an in vitro assay that predicts the efficacy of novel homocysteine lowering therapies.

Elevated plasma total homocysteine (tHcy) is a risk factor for atherosclerosis. Hcy is 70-80% bound to albumin as a disulfide. Recent trials have evaluated ability of thiol-containing drugs to exchange with protein bound Hcy and consequently increase its renal clearance. The objective of this study was to develop an in vitro assay to predict the efficacy of thiol-containing drugs to lower tHcy in the clinical setting. The assay was used to test the effects of N-acetylcysteine (NAC), mesna, captopril, dimercaptosuccinic acid (DMSA), and penicillamine. Hcy was added in vitro to plasma of healthy subjects (n = 6) and equilibrated. Concentrations of thiol exchange agent were added and incubated at 37 degrees C. Aliquots were removed at selected intervals and free Hcy determined. Mesna, captopril, and NAC caused a concentration-dependent increase in free Hcy. Three-hundred micromolar mesna and captopril had a greater effect than equimolar NAC, increasing free Hcy by 33.9 +/- 5.0% and 32.0 +/- 2.6%, respectively compared to 22.3 +/- 2.4% for NAC, p < 0.001. Our in vitro results indicate that mesna, captopril, and NAC effectively exchange with covalently bound Hcy. This assay can act as screening tool for novel tHcy lowering therapies and should spare the expense of negative trials.

Dimercaptosuccinic acid for the treatment of hyperhomocysteinemia in hemodialysis patients: a placebo-controlled, double-blind, randomized trial.

BACKGROUND: Elevated total homocysteine (tHcy) levels may represent a potentially modifiable risk factor for cardiovascular disease in hemodialysis patients. Current therapies, including multivitamins, have been ineffective at normalizing homocysteine levels in this population; hence, new therapies are needed. There is increasing interest in the use of thiol pharmaceutical agents to displace homocysteine from albumin and improve its dialyzability. We designed a randomized, double-blind, placebo-controlled trial to determine the effect of prolonged administration of oral dimercaptosuccinic acid (DMSA) on plasma tHcy levels in vitamin-replete hemodialysis patients. METHODS: Forty-four long-term stable dialysis patients were treated for a minimum of 4 weeks with a standard multivitamin, ensuring a vitamin-replete state, then matched on the basis of tHcy levels and randomly assigned as pairs to the administration of DMSA, 2.5 mg/kg/d, or identical placebo for 8 weeks. Multivitamins were continued for the duration of the trial. RESULTS: Thirty-eight subjects (including 16 pairs) completed the trial. All important determinants of homocysteine level were balanced, and the only significant baseline difference was weight (P = 0.02). At 8 weeks, by paired analysis, there was no statistically significant difference in tHcy levels between the placebo and DMSA groups, at 21.2 micromol/L (2.87 mg/L) and 22.6 micromol/L (3.06 mg/L), respectively (mean difference, -1.4; 95% confidence interval, -5.3 to 2.5; P = 0.45). The same was true for unpaired and multivariable analyses. CONCLUSION: This randomized placebo-controlled trial found that prolonged oral administration of the thiol DMSA had no impact on tHcy levels in hemodialysis patients. Additional strategies to test the homocysteine hypothesis in this population require investigation.

A flavonoid fraction from cranberry extract inhibits proliferation of human tumor cell lines.

In light of the continuing need for effective anticancer agents, and the association of fruit and vegetable consumption with reduced cancer risk, edible plants are increasingly being considered as sources of anticancer drugs. Cranberry presscake (the material remaining after squeezing juice from the berries), when fed to mice bearing human breast tumor MDA-MB-435 cells, was shown previously to decrease the growth and metastasis of tumors. Therefore, further studies were undertaken to isolate the components of cranberry that contributed to this anticancer activity, and determine the mechanisms by which they inhibited proliferation. Using standard chromatographic techniques, a warm-water extract of cranberry presscake was fractionated, and an acidified methanol eluate (Fraction 6, or Fr6) containing flavonoids demonstrated antiproliferative activity. The extract inhibited proliferation of 8 human tumor cell lines of multiple origins. The androgen-dependent prostate cell line LNCaP was the most sensitive of those tested (10 mg/L Fr6 inhibited its growth by 50%), and the estrogen-independent breast line MDA-MB-435 and the androgen-independent prostate line DU145 were the least sensitive (250 mg/L Fr6 inhibited their growth by 50%). Other human tumor lines originating from breast (MCF-7), skin (SK-MEL-5), colon (HT-29), lung (DMS114), and brain (U87) had intermediate sensitivity to Fr6. Using flow cytometric analyses of DNA distribution (cell cycle) and annexin V-positivity (apoptosis), Fr6 was shown in MDA-MB-435 cells to block cell cycle progression (P < 0.05) and induce cells to undergo apoptosis (P < 0.05) in a dose-dependent manner. Fr6 is potentially a source of a novel anticancer agent.

Autonomic signs and dosing during the initial stages of clozapine therapy.

BACKGROUND: Recent reports implicate clozapine in heart rate variability, QTc prolongation, torsade de pointes and sudden death at therapeutic doses, even in physically healthy patients. This study aims to examine whether autonomic (vital) signs are correlated with clozapine dose titration and blood levels of clozapine and nor-clozapine during clozapine therapy. MATERIAL/METHODS: Thirty-seven consecutive patients with diagnosis of schizophrenia treated with clozapine were included in this prospective longitudinal study. The study was restricted to only the first 8 weeks of treatment. After obtaining informed consent, serum concentrations of clozapine and nor-clozapine were determined weekly at trough, as doses were administered q12h and adjusted according to clinical guidelines for clozapine use. Autonomic signs including BP (supine and erect), pulse (supine and erect) and temperature were monitored daily each morning before and one hour after the morning's dose of clozapine was administered. RESULTS: We calculated analyses of covariance (ANCOVAs) to evaluate the changes in vital signs parameters, from baseline to week 8, with clozapine variables as covariates (i.e, the dose of clozapine, as well as the levels of serum clozapine and nor-clozapine). The blood pressure and pulse did not change significantly (p<0.01) from baseline to weeks 8. The temperature was inversely related to clozapine dose (p<0.003). Higher nor-clozapine to clozapine ratios were associated with higher BP measures (p=0.002). The magnitude of these relationships is weak (r<0.30). CONCLUSIONS: There is a tendency to autonomic dysregulation during clozapine use. This has cardiac function implications, justifying cautious dose adjustment with frequent monitoring of vital signs.

Monitoring clozapine: are fingerprick blood and plasma clozapine levels equivalent to arm venipuncture blood and plasma levels?

The objective of this pilot study was to determine whether fingerprick blood and plasma clozapine levels were equivalent to arm venipuncture blood and plasma levels for the purpose of therapeutic monitoring. A convenient sample of 10 outpatients from the Elgin Program of Assertive Community Treatment Team (PACT) participated in the study. Blood samples were obtained simultaneously from both the arm and finger in patients at steady state to measure clozapine levels. Each site provided a blood and plasma clozapine level, and they were compared. Clozapine levels from arm and finger sites were found to be equivalent in both blood and plasma. Although plasma clozapine levels were consistently greater than those in whole blood by a mean value of 27%, the plasma therapeutic threshold level (350-400 micro g/L) was considered an adequate target for monitoring. A fingerprick blood sample of 50 micro L was sufficient to measure clozapine levels accurately at steady state. We therefore concluded that fingerprick blood testing is as effective as the traditional arm venipuncture method in obtaining accurate clozapine levels. This procedure may provide certain benefits for the seriously mentally ill.

Relative bioavailability and antioxidant potential of two coenzyme q10 preparations.

Coenzyme Q10 (CoQ10) is synthesized by the human body and found in certain foods. Daily supplementation of CoQ10 could protect against heart disease but the bioavailability of CoQ10 supplements depends on the formulation taken. We compared the bioavailability and antioxidant properties of two commercial CoQ10 formulations, a commercial grade CoQ10 powder (commercial grade CoQ) and a new BT-CoQ10 BIO-TRANSFORMED (BT-CoQ10) obtained by fermentation of a soy-based, CoQ10-rich media with baker's yeast. Eleven healthy individuals participated in a randomized two-way crossover trial, with a 3-week washout period. Capsules containing 300 mg of either BT-CoQ10 or commercial grade CoQ10 were given daily for 1 week and multiple blood samples were taken for CoQ10, glutathione and glutathione peroxidase (GPx) determination. In 3 subjects, baseline plasma CoQ10 levels were lower prior to BT than prior to commercial grade CoQ treatment. In the remaining participants, ingestion of BT vs. commercial grade CoQ significantly increased maximum plasma CoQ10 concentration (+126%, p = 0.04) and tended to increase CoQ10 area under the curve from 0 to 24 h (+160%, p = 0.07). One week of treatment with each formulation increased plasma CoQ10 but did not alter plasma glutathione or GPx activity. The enhanced bioavailability of the BT product might be due to its predominantly reduced, hydrophilic membrane-complex form.

Relation of blood counts during clozapine treatment to serum concentrations of clozapine and nor-clozapine.

OBJECTIVE: To determine the relation between serum clozapine and nor-clozapine levels and blood cell counts during clozapine treatment. METHOD: We undertook a prospective longitudinal study of 37 consecutive patients with a diagnosis of schizophrenia treated with clozapine. We obtained informed consent and then determined serum concentrations of clozapine and nor-clozapine weekly. Clozapine was administered daily in divided doses given every 12 hours and adjusted according to clinical guidelines for its use. Samples for serum concentrations were taken at steady state, immediately before the next morning's dose, for 4 to 8 weeks. Complete blood counts (CBC), weight, and vital signs (that is, blood pressure, pulse, and temperature) were also monitored weekly before the morning's dose of clozapine was administered. RESULTS: Analyses of variance showed no significant changes over the 8-week treatment course in the observed mean white blood count (WBC), red blood count (RBC), neutrophils, and lymphocytes counts, or in the hemoglobin and hematocrit. Only a few weak correlations (r < 0.21) were found between these hematological parameters and the measures of serum clozapine and nor-clozapine. CONCLUSIONS: The mechanism of clozapine-induced hematotoxicity at the therapeutic dosage range is probably not by direct toxicity of clozapine or nor-clozapine to the blood cells or their precursors. The formation of the cytotoxic nitrenium compound from clozapine by neutrophils may be necessary.