Enantioselective disposition of clenbuterol in rats.

Clenbuterol is a long-acting ß2-adrenoceptor agonist and bronchodilator that is used for the treatment of asthma, but the desired activities reside almost exclusively in the (-)-R-enantiomer. This study examined enantioselectivity in the disposition of clenbuterol following administration of clenbuterol racemate to rats. Concentrations of clenbuterol enantiomers in plasma, urine and bile were determined by LC-MS/MS assay with a Chirobiotic T column. This method was confirmed to show high sensitivity, specificity and precision, and clenbuterol enantiomers in 0.1 ml volumes of plasma were precisely quantified at concentrations as low as 0.25 ng/ml. The pharmacokinetic profiles of clenbuterol enantiomers following intravenous and intraduodenal administration of clenbuterol racemate (2 mg/kg) in rats were significantly different. The distribution volume of (-)-R-clenbuterol (9.17 l/kg) was significantly higher than that of (+)-S-clenbuterol (4.14 l/kg). The total body clearance of (-)-R-clenbuterol (13.5 ml/min/kg) was significantly higher than that of the (+)-S-enantiomer (11.5 ml/min/kg). An in situ absorption study in jejunal loops showed no difference in the residual amount between the (-)-R- and (+)-S-enantiomers. Urinary clearance was the same for the two enantiomers, but biliary excretion of (-)-R-clenbuterol was higher than that of the (+)-S-enantiomer. The fractions of free (non-protein-bound) (-)-R- and (+)-S-clenbuterol in rat plasma were 48.8% and 33.1%, respectively. These results indicated that there are differences in the distribution and excretion of the clenbuterol enantiomers, and these may be predominantly due to enantioselective protein binding.

Gosha-jinki-gan reduced oxaliplatin-induced hypersensitivity to cold sensation and its effect would be related to suppression of the expression of TRPM8 and TRPA1 in rats.

Peripheral neuropathy is a common side effect of the chemotherapeutic agent oxaliplatin (Oxp), and is associated with hypersensitivity to cold sensation in the acute stage. Recently, gosha-jinki-gan (GJG), a Japanese herbal medicine, was reported to improve Oxp-induced cold hypersensitivity. However, the mechanism for this effect was not elucidated. We hypothesized that the effect of GJG on Oxp-induced cold hypersensitivity may be associated with the expression of the transient receptor potential melastatin 8 (TRPM8) and transient receptor potential ankyrin 1 (TRPA1) channels, which are cold-gated ion channels. To assess this hypothesis, we examined alteration of the withdrawal response to cold stimulation following coadministration of GJG and Oxp in rats, and the relationship between this altered withdrawal response and the expression of TRPM8 and TRPA1 mRNA in the dorsal root ganglia (DRG). Assessment of cold hypersensitivity was performed at 4 and 10°C using a cold plate. Compared with Oxp administration alone, coadministration of GJG (oral dose: 1 g/kg/day for 12 days) and Oxp (intraperitoneal dose: 4 mg/kg twice a week) significantly reduced the withdrawal response to cold stimulation. On the 12th day of drug administration, the L4-L6 DRG were removed and the expression of TRPM8 and TRPA1 mRNA was determined using RT-PCR. The expression of TRPM8 and TRPA1 in the DRG of rats that were coadministered GJG and Oxp decreased significantly compared with that in the rats administered Oxp alone. These results suggest that coadministration of GJG may improve Oxp-induced cold hypersensitivity by suppressing the overexpression of TRPM8 and TRPA1 mRNA.

[Face-to-face questionnaire survey on the use of multiple antipsychotics and the manifestation of side effects in outpatients with schizophrenia].

We investigated the use of multiple antipsychotics and the manifestation of side effects in outpatients with schizophrenia and compared the results of patients who received 1 antipsychotic (monotherapy) with those of patients who received more than 1 antipsychotic (multidrug therapy). To achieve this, we visited 8 community life-support centers and conducted a face-to-face questionnaire survey with 47 outpatients. Sixteen (34%) of these patients had received monotherapy and 31 (66%), multidrug therapy. Complaints involving the central nervous system, anticholinergic symptoms, metabolic symptoms (weight gain, increase in blood glucose, etc.), and extrapyramidal symptoms were seen across the patients. The average incidence of side effects was 2.2 per person in the monotherapy group and 4.8 in the multidrug-therapy group. The number of nonantipsychotic drugs used concomitantly in the monotherapy group was also smaller than that used in the multidrug-therapy group (2.3 and 5.0 per person, respectively). Further, we analyzed the 47 patients as described above; 20 patients received typical antipsychotics (TA group), 10 patients received atypical antipsychotics (AA group), and 17 patients received both typical and atypical antipsychotics (MIX group). The average incidence of side effects in the TA, AA, and MIX groups was 2.8, 3.2, and 5.5 per person, respectively, and the number of nonantipsychotic drugs used concomitantly was 2.2, 3.2, and 6.1, respectively. On the basis of our results, it can be suggested that monotherapy with an atypical antipsychotic can reduce both the number of nonantipsychotic drugs used concomitantly and the average incidence of side effects.

Effects of anti-malarial drugs on the electrocardiographic QT interval modelled in the isolated perfused guinea pig heart system.

BACKGROUND: Concern over the potential cardiotoxicity of anti-malarial drugs inducing a prolonged electrocardiographic QT interval has resulted in the almost complete withdrawal from the market of one anti-malarial drug - halofantrine. The effects on the QT interval of four anti-malarial drugs were examined, using the guinea pig heart. METHODS: The guinea pig heart was isolated, mounted on a Langendorff apparatus, and was then perfused with pyruvate-added Klebs-Henseleit solutions containing graded concentrations of the four agents such as quinidine (0.15 - 1.2 µM), quinine (0.3 - 2.4 µM), halofantrine (0.1 - 2.0 µM) and mefloquine (0.1 - 2.0 µM). The heart rate-corrected QaTc intervals were measured to evaluate drug-induced QT prolongation effects. RESULTS: Quinidine, quinine, and halofantrine prolonged the QaTc interval in a dose-dependent manner, whereas no such effect was found with mefloquine. The EC50 values for the QaTc prolongation effects, the concentration that gives a half-maximum effect, were quinidine < quinine ≈ halofantrine. CONCLUSIONS: In this study, an isolated, perfused guinea pig heart system was constructed to assess the cardiotoxic potential of anti-malarial drugs. This isolated perfused guinea pig heart system could be used to test newly developed anti-malarial drugs for their inherent QT lengthening potential. More information is required on the potential variation in unbound drug concentrations in humans, and their role in cardiotoxicity.

Influence of single-nucleotide polymorphisms in the multidrug resistance-1 gene on the cellular export of nelfinavir and its clinical implication for highly active antiretroviral therapy.

Protease inhibitors (PIs) such as nelfinavir (NFV) suppress HIV replication. PIs are substrates of P-glycoprotein (P-gp), the product of the multidrug-resistance-1 (MDR1) gene. Three single-nucleotide polymorphisms (SNPs) are present in exons of the MDR1 gene: MDR1 1236, MDR1 2677 and MDR1 3435. We speculated that these genetic polymorphisms affected PI concentration in the cell. To verify this hypothesis, we first genotyped these SNPs in 79 Japanese patients by the SNaPshot method and found incomplete linkage disequilibrium between the SNPs. Because the SNP at MDR1 3435 has been reported to be associated with P-gp expression, we evaluated the effect of that SNP on the export of NFV from HIV-positive patients' lymphoblastoid cell lines by measuring time-dependent decrease in the amount of intracellular NFV by high-performance liquid chromatography. We found the intracellular concentration of NFV in lymphoblastoid cell lines (LCLs) with the homozygous T/T genotype at MDR1 3435 were higher than that with C/C genotype with statistical significance. This suggests that the activity of P-gp in patients' LCL cells with the MDR1 3435 T/T genotype was lower. In a retrospective study we evaluated the effect of the SNPs on CD4 cell count recovery in response to antiretroviral treatment with PIs, and obtained statistically significant evidence that suggested marginal association of the SNP at MDR1 1236 but not at MDR1 2677 or MDR1 3435. As in vitro results were not consistent with the clinical evaluation, clinical importance of MDR1 genotyping for antiretroviral therapy remains to be investigated in a larger, case-controlled study.

Inhibitory effect of erythromycin on potassium currents in rat ventricular myocytes in comparison with disopyramide.

Disopyramide, a class Ia antiarrhythmic agent, has been reported to induce torsades de pointes (TdP) associated with excessive QT prolongation in electrocardiogram (ECG), especially when concomitantly administered with erythromycin, a macrolide antibiotic agent. In this study, we have evaluated the effects of erythromycin on action potential duration (APD) and potassium currents in rat ventricular myocytes in comparison with disopyramide. We have evaluated the relationship between in-vitro potassium current inhibition and in-vivo QT prolongation observed in a previous study. Action potentials and membrane potassium currents, including delayed rectifier current (I(K)) and transient outward current (I(to)), were recorded using a whole-cell patch clamp method in enzymatically-dissociated ventricular cells. Erythromycin and disopyramide prolonged APD in a concentration-dependent manner. Disopyramide (10-100 microM) and erythromycin (100 microM) led to increases in the APD at 90% repolarization level. Disopyramide reduced I(K) (IC50 = 37.2 +/- 0.17 microM) and I(to) (IC50 = 20.9 +/- 0.13 microM) while erythromycin reduced I(K) (IC50 = 60.1 +/- 0.29 microM) but not I(to). The observed prolongation of APD might be ascribed to the inhibition of potassium currents. Erythromycin produced the prolongation of APD and the inhibition of potassium currents with a lag time after addition of the drugs, which suggested that erythromycin might not reach potassium channels from outside the ventricular cells. The potency of disopyramide was almost equivalent under in-vitro and in-vivo conditions. However, potency of erythromycin in-vitro was far weaker than that in-vivo reported in a previous study, presumably due to a difference in the uptake of erythromycin into ventricular myocytes between in-vivo and in-vitro conditions. Therefore, when drug-induced risks of QT prolongation are to be evaluated, the difference of potencies between in-vitro and in-vivo should be taken into consideration.

Pharmacokinetic and pharmacodynamic analyses, based on dopamine D2-receptor occupancy of bromocriptine, of bromocriptine-induced contralateral rotations in unilaterally 6-OHDA-lesioned rats.

Bromocriptine is a selective agonist for dopamine D2-receptors and is used in the treatment of Parkinson's disease. In this study, we performed pharmacokinetic and pharmacodynamic (PK/PD) analyses of the antiparkinsonian effect of bromocriptine and evaluated drug-induced contralateral rotations in rats in which unilateral striatal lesions had been generated by microinjection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. The plasma concentration (Cp) and D2 receptor occupancy (Phi(D2)) were quantitated by HPLC and with an in vivo back-titration method using [(3)H]-raclopride, respectively. Bromocriptine induced contralateral rotations (E(rot)) in a dose-dependent manner following intraperitoneal administration in an animal model of Parkinson's disease. The Cp of bromocriptine peaked at 15-30 min after the administration and decreased time-dependently, whereas the Phi(D2) of bromocriptine increased gradually for 180 min after administration. The relationship between Cp and E(rot) exhibited an anticlockwise hysteresis, whereas the relationship between Phi(D2) and E(rot) showed a linear correlation. These results suggest that in vivo Phi(D2) is a good pharmacological indicator of the effect of a D2 agonist.

Recommendations for the treatment of fungal pneumonias.

Incidences of fungal pneumonias have increased in immunocompromised patients with HIV infection or receiving bone marrow replacement or solid organ transplantation. Fungal pneumonias including aspergillosis, cryptococcosis, candidiasis, coccidioidomycosis, histoplasmosis and blastomycosis are one of the major causes of morbidity and mortality among the immunosuppressed hosts. Therefore, clinicians should consider the most appropriate and aggressive treatment of fungal pneumonias in this population. This report outlines the state of the art in the treatment of fungal pneumonias and discusses recent advances in antifungal therapy. Practice guidelines for the treatment with commonly used antifungal agents including amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine, are very useful for clinicians to manage the diseases appropriately. Echinocandins and second-generation triazoles will hopefully help clinicians to overcome the limitations of the current therapy.

[Evaluation of the permeability of corticosteroid in hairless mouse and hairless micropig skin from admixture of commercially available corticosteroid ointments and/or creams].

Yucatan hairless micropig (YHMP) skin has been shown to have histology and physiologic properties similar to human skin. To assess the relationship between the permeability of corticosteroid ointments and five types of commonly used admixtures of corticosteroid through hairless mice (HM) or YHMP skin and the clinical effects in humans, we conduct by in vitro experiments using HM and YHMP skin. The permeability of corticosteroid in admixtures with urea or heparinoid ointments across HM or YHMP skin was 1.5-4-fold greater than that of corticosteroid ointments alone. HM skin was found to have faster permeability than YHMP skin, but otherwise was similar to YHMP skin. These experiments demonstrated a close relationship between the permeability of HM or YHMP skin and vasoconstrictor activity in humans. These results suggest that the in vitro permeability of corticosteroid measurements across HM skin could be a useful, rapid, and easy method for assessing the vasoconstrictor activity of topical corticosteroids and the admixtures of commercially available ointments and/or creams in humans.

[Effect of grapefruit pulp on the pharmacokinetics of the dihydropyridine calcium antagonists nifedipine and nisoldipine].

The effect of the intake of 200 g of grapefruit pulp (corresponding to one grapefruit) on the pharmacokinetics of the calcium antagonists nifedipine (NF) and nisoldipine (NS) were investigated in 8 healthy Japanese male volunteers. A crossover design was used for the study: group I did not ingest any grapefruit (control group); group II ingested grapefruit 1 h after drug administration; and group III ingested grapefruit 1 h before drug administration. The intake of grapefruit pulp increased the plasma concentrations of both NF and NS, an effect that has previously been reported with grapefruit juice. The increase was most marked when grapefruit was eaten before drug administration. For both NF and NS, subjects who ingested grapefruit 1 h before drug administration exhibited a greater Cmax and AUC0-24 than did subjects in the control group. For NF, the Cmax was 1.4 times higher and the AUC0-24 1.3 times larger in group III than in group I. For NS, the Cmax was 1.5 times higher and the AUC0-24 1.3 times larger in group III than in group I. The increase in the AUC0-24 was significant for both drugs (p < 0.05). The finding that the ratios of Cmax and AUC0-24 for unchanged drug and metabolites did not vary greatly among the three groups for either drug suggests that the increase in serum concentration produced by grapefruit intake may be due to other factors than an inhibitory effect on drug metabolism. Also, the increases in Cmax and AUC0-24 of NS produced by grapefruit intake were smaller than those produced by grapefruit juice intake, indicating that grapefruit pulp and juice have different effects on the pharmacokinetics.

[Effect of admixture of commercially available corticosteroid ointments and/or creams on vasoconstrictor activity].

A commonly used admixture of commercially available ointments and/or creams was selected from the prescribed sheets in our hospital, and questionnaire to dermatologists. To assess the relationship between permeability of corticosteroid through murine skin and clinical effects in human, we attempted to investigate the vasoconstrictor activity of these admixtures of topical corticosteroid by double-blind controlled study. Test samples were occluded at random on the back of 20 healthy volunteers for 4 hours. The vasoconstrictor activity of corticosteroid creams (Lidomex) alone was significantly large as compared with that of ointments alone. The vasoconstrictor activity of corticosteroid in the admixture of Lidomex ointment and urea ointments or heparinoid ointment was 1.5-2 fold significantly larger than that from ointments alone. The extent of the stability of the emulsion after mixing was related to the vasoconstrictor activity. These experiments demonstrated a close relationship between the vasoconstrictor activity of human skin and permeability of hairless mice skin. These results suggested that the vasoconstrictor activity of topical corticosteroids mixed with commercially available ointments and/or creams depends upon their physicochemical characteristics.