Potential of pranlukast and zafirlukast in the inhibition of human liver cytochrome P450 enzymes

1. The potential of zafirlukast to inhibit several human cytochrome P450 enzymes is well known. However, pranlukast, a structural analogue of zafirlukast, has not been studied. Accordingly, the inhibitory potential of pranlukast was evaluated and compared with that of zafirlukast, a known CYP2C9 inhibitor, in in vitro microsomal incubation studies. 2. Both pranlukast and zafirlukast showed moderate inhibition of CYP2C9-catalysed tolbutamide 4-methylhydroxylation, competitively inhibiting tolbutamide 4-methylhydroxylation with estimated mean K(i) values of 3.82 +/- 0.50 and 5.86 +/- 0.08 microM, respectively. 3. Pranlukast had no effect on CYP2C19-catalysed S-mephenytoin 4'-hydroxylation or CYP3A4-catalysed midazolam 1-hydroxylation. However, zafirlukast showed minor inhibition of these reactions. Neither pranlukast nor zafirlukast inhibited CYP1A2-catalysed phenacetin O-deethylation, CYP2D6-catalysed dextromethorphan O-demethylation or CYP2E1-catalysed chlorzoxazone 6-hydroxylation. 4. The results suggest that like zafirlukast, pranlukast also has the potential moderately to inhibit CYP2C9-catalysed tolbutamide 4-methylhydroxylation. Therefore, the inhibitory potential of pranlukast should be considered when it is co-administered with CYP2C9 substrates with narrow therapeutic ranges (e.g. S-warfarin, phenytoin).

An adaptive M-wave canceler for the EMG controlled functional electrical stimulator and its FPGA implementation

Biopotential signals have been used as command and feedback signals in systems using electrical stimulation of motor nerves to restore the lost function. In order to use the voluntary electromyography (EMG) as a control signal for the functional electrical stimulation of the same muscle, it is necessary to suppress the M-wave evoked by the electrical stimulation. We present a Gram-Schmidt (GS) prediction error filter which effectively eliminates the M-wave from voluntary EMG. The GS filter has systolic array structure, so it offers advantages for the real-time processing on the field programmable gate array (FPGA). On basis of the data obtained from model for M-wave and voluntary EMG and from CNS injury patient, the proposed GS filter showed a very promising performance.

The analysis of mental stress using time-frequency distribution of heart rate variability signal

Conventional power spectrum methods based on fast Fourier transform (FFT), autoregressive(AR) model are not appropriate for analyzing biomedical signals whose spectral characteristics change rapidly. On the other hand, time-frequency analysis has more desirable characteristics of a time-varying spectrum. In this study, we investigated the spectral components of heart rate variability (HRV) in a time-frequency domain. Then, from the instantaneous frequency, obtained from time-frequency distribution, the method extracting frequency components of HRV was proposed. The subjects were 17 healthy young men. A coin-stacking task was used to induce mental stress. In the results, the emotional stress of subjects produced an increase in sympathetic activity. Sympathetic activation was responsible for the significant increase in the LF/HF ratio. The subjects were divided into two groups with task ability. The subject who had higher mental stress had a lack of task ability.

Chronic stress evaluation using neuro-fuzzy

The purpose of this research was to evaluate chronic stress using physiological parameters. Wistar rats were exposed to sound stress for 14 days. Biosignals were acquired hourly. To develop a fuzzy inference system that can integrate physiological parameters, the parameters of the system were adjusted by the adaptive neuro-fuzzy inference system. Of the training dataset, the input dataset was the physiological parameters from the biosignals and the output dataset was the target values from the cortisol production. Physiological parameters were integrated using the fuzzy inference system, then 24-hour results were analyzed by the Cosinor method. Chronic stress was evaluated from the degree of circadian rhythm disturbance. Suppose that the degree of stress for initial rest period was 1. Then, the degree of stress after 14-day sound stress increased to 131, and increased to 1.47 after the 7-day recovery period. That is, the rat was exposed to 37%increased amount of stress by the 14-day sound and did not recover after the 7-day recovery period.

Association between CYP2D6 genotype and tardive dyskinesia in Korean schizophrenics

The CYP2D6 gene codes for human cytochrome P450 2D6 enzyme, which is responsible for the metabolism of many psychiatric drugs. In schizophrenic patients treated with neuroleptics, decreased or loss of function CYP2D6 alleles may contribute to the development of tardive dyskinesia (TD), a movement disorder that frequently occurs with chronic neuroleptic treatment. The goal of this study was to determine whether the occurrence of TD is associated with CYP2D6 genotype in a cohort of Korean schizophrenics by employing a CYP450 GeneChip((R)) oligonucleotide microarray and PCR assays to screen for 19 CYP2D6 alleles. Our results revealed that males with at least one decreased or loss of function allele have a moderately greater chance of developing TD than males with only wild-type alleles. Female schizophrenics did not have a significantly greater chance of developing TD. Our results demonstrate the utility of CYP2D6 microarrays to assess genotype status in this Korean cohort.

Rate-adaptive pacemaker controlled by motion and respiratory rate using neuro-fuzzy algorithm

Rate-adaptive pacemakers use information from sensors to change the rate of heart stimulation. Until now, fuzzy-pacemaker algorithms have been used to combine inputs from sensors to improve heart rate control, but they have been difficult to implement. In this paper, a pacemaker algorithm which controlled heart rate adaptively by motion and respiratory rate was studied. After chronotropic assessment exercise protocol (CAEP) tests were performed to collect activity and respiratory rate signals, the intrinsic heart rate was inferred from these two signals by a neuro-fuzzy method. For 10 subjects the heart rate inference, using the neuro-fuzzy algorithm, gave 52.4% improved accuracy in comparison with the normal fuzzy table look-up method. The neuro-fuzzy method was applied to a real pacemaker by reduced mapping of the neuro-fuzzy look-up table.

Frequency of cytochrome P450 2C9 mutant alleles in a Korean population

AIMS

To determine the frequencies of CYP2C9 variants in the Korean population and compare them with the frequencies in other ethnic populations.

METHODS

Genotyping of CYP2C9*2 and CYP2C9*3 allelic variants was carried out in 574 Korean subjects by PCR and restriction fragment length pattern analysis.

RESULTS

Thirteen of 574 subjects (2.3%) were heterozygous for CYP2C9*3 (Ile359Leu), but no subjects with a CYP2C9*2 allele or homozygous for CYP2C9*3 were identified. The allele frequency of CYP2C9*3 in Korean subjects (0.0113, 95% CI 0.0066-0.0193) was similar to that of other East Asian populations, but was considerably lower than that of Caucasian populations.

CONCLUSIONS

CYP2C9*3 seems to be an allelic variant related to the functional polymorphism of CYP2C9, but this variant is rarely seen among Koreans compared with Caucasians. Routine genotyping of the CYP2C9*2 allele is considered to be unnecessary in Korean and East Asians, because this allele appears to be extremely rare or absent in these populations.

Relationship of paroxetine disposition to metoprolol metabolic ratio and CYP2D6*10 genotype of Korean subjects

OBJECTIVE

To evaluate the relationship between the metabolic ratio (MR) of metoprolol, CYP2D6*10B genotype, and the disposition of paroxetine in Korean subjects.

METHODS

A single 40-mg dose of paroxetine was administered orally to one poor metabolizer and 15 healthy subjects recruited from 223 Korean extensive metabolizers whose phenotypes were predetermined by use of the metoprolol MR. Genotypes were determined by allele-specific polymerase chain reaction and the GeneChip microarray technique. Pharmacokinetic parameters were estimated from plasma concentrations of paroxetine for more than 240 hours after the oral dose.

RESULTS

The oral clearance and area under the plasma concentration versus time curve (AUC) of paroxetine were best described by a nonlinear relationship with metoprolol MR at correlation coefficients of 0.82 and 0.91, respectively (P < .05). Nine extensive metabolizer who were either homozygous or heterozygous for CYP2D6*10B had significantly lower oral clearance values of paroxetine than six extensive metabolizers with CYP2D6*1/*1. The AUC of paroxetine in subjects who were homozygous for CYP2D6*10B (666.4 +/- 169.4 ng/mL x h) was significantly greater than that of subjects who were homozygous for the wild type (194.5 +/- 55.9 ng/mL x h). Unexpectedly, the average AUC of subjects who were heterozygous for CYP2D6*10B was greater with wide variation (789.8 +/- 816.9 ng/mL x h) than that of subjects who were homozygous CYP2D6*10B/*10B mainly because of two atypical subjects whose metoprolol MR was not associated with the CYP2D6*10B genotype and who showed greater AUC and lower oral clearance than subjects with homozygous CYP2D6*10B.

CONCLUSIONS

The CYP2D6 activity measured by metoprolol MR was a strong predictor of paroxetine disposition in Korean extensive metabolizers. In general, the extensive metabolizers with the CYP2D6*10B allele seemed to have higher plasma concentrations of paroxetine than extensive metabolizers with the wild-type CYP2D6 genotype. However, quantitative prediction of paroxetine disposition from the CYP2D6*10B genotype alone was not perfect because several Korean extensive metabolizers had metoprolol MRs that were not associated with the genotype.

Multicenter study of the treatment of erectile dysfunction with transurethral alprostadil (MUSE) in Korea

A Korean multicenter study was conducted to assess the effectiveness of transurethral alprostadil with MUSE in 334 subjects with chronic erectile dysfunction (ED) who were enrolled in 21 clinical centers. Patients with psychogenic impotence comprised about 30% of subjects. Intraurethral alprostadil was titrated in a stepwise fashion in the clinics from 250 to 500 or 1000 mcg based on erectile response and tolerability. The erectile responses were evaluated using an erection assessment scale (score of 1-5). The dose that produced a maximal penile response of score 5 (full rigid erection) or 4 (full tumescence, partial rigidity) was selected for home treatment. Patients who showed partial erection (score of 3) with 1000 mcg were also included in the home-treatment group. In-clinic phase: 198 men (59.3%) had maximal penile responses of score 4 or 5. The rate of maximal responses was not related to patient age, etiology or duration of the ED. A total of 228 (68.3%) men progressed to home treatment. The overall level of comfort of the transurethral alprostadil was rated as uncomfortable or very uncomfortable in 12%. Home phase: During the two-month period of home treatment, 178 (78.1%) men had successful sexual intercourse at least once, and 78.2% of administrations (1976) resulted in successful intercourse. The main causes of drop-out were insufficient erectile response in 27 men (11.8%), adverse reactions (mostly penile or urethral pain) in 7 (3.1%) or both in 7 (3.1%). In conclusion, transurethral alprostadil could be a suitable treatment option for patients with ED regardless of age and etiology of ED. Efficacy in an Asian population (Korea) is comparable to that reported previously in Caucasians.

Rapid simple high-performance liquid chromatographic determination of paroxetine in human plasma

A rapid, simple method for the measurement of paroxetine in human plasma by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection is described. This method includes only one-step extraction of paroxetine and dibucaine, an internal standard, with chloroform. Their recoveries were around 90%. The mobile phase, 10 mM phosphate buffer-acetonitrile (40:60, v/v) was eluted isocratically. Between- and within-day coefficients of variation were in the range of 1.9-9.4% and 2.3-13.3%, respectively. The detection limit was 0.2 ng/ml. The method we describe can be easily applied to the measurement of plasma paroxetine concentration for pharmacokinetic studies as well as for therapeutic drug monitoring in patients taking paroxetine.

Interlimb interaction and stabilization of contralateral leg in isokinetic knee evaluation

OBJECTIVE

To determine if peak torque (PT) production during isokinetic knee testing is affected by the stabilization and movement patterns of the contralateral leg.

DESIGN

Repeated measure design.

INTERVENTION AND MAIN OUTCOME MEASURE

Thirty subjects participated in comparing the force outputs in relation to the movement pattern of both legs. Another group of 45 subjects volunteered to perform five maximal isokinetic extension-flexion contractions in each of three different knee testing conditions: (1) without stabilization of the contralateral leg; (2) with a bar in front of the ankle joint of the contralateral leg; (3) with the contralateral leg strapped just above the level of the malleoli and the muscles of that leg induced reciprocally to perform isometric contractions with respect to the testing leg. PT was used to compare the strength of three different conditions.

RESULTS

Significantly greater PT was measured when the contralateral leg of the subject was fixed and induced to contract reciprocally.

CONCLUSION

More rigorous standardization of isokinetic strength testing procedures is needed due to differences in PT production of knee muscles according to the stabilization and movement pattern of the contralateral leg.

Effect of rifampin on the plasma concentration and the clinical effect of haloperidol concomitantly administered to schizophrenic patients

We assessed the changes of plasma haloperidol concentrations and clinical responses repeatedly up to 4 weeks after coadministration or discontinuation of rifampin in 12 schizophrenic patients taking haloperidol alone (group I) and 5 patients taking haloperidol and antituberculotic drugs (group II). After coadministration of rifampin in group I, daily trough haloperidol concentrations rapidly decreased and reached 63% of baseline level by day 3, 41.3% by day 7, and 30% by day 28. On the other hand, after discontinuation of rifampin in group II, plasma haloperidol concentration increased to 140.7% of baseline level by day 3, 228.7% by day 7, and 329% by day 28. In this study, a 30% or greater change in the clinical rating scale was considered a positive clinical response of the drug interaction. Using this criterion, 50% of the group I subjects responded according to the Brief Psychiatric Rating Scale (BPRS) total score, and 25% responded according to the BPRS subscale for psychiatric symptoms. No positive responses were observed in group II patients. These results strongly suggest that rifampin interacts with the clinical effects as well as the plasma concentrations of coadministered haloperidol, and careful monitoring should be considered when coadministration or discontinuation of rifampin is needed in a schizophrenic patient taking haloperidol.