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PubMed1987

[In vitro tests of hepatic oxidation in man, predictive of drug interactions].

Liver monooxygenases are of primary importance in the metabolism of numerous drugs. Their activity, which is genetically controlled, is modulated by environmental factors such as drug treatment. We have developed an in vitro model of human oxidative metabolism in order to evaluate the activity of a specific monooxygenase (debrisoquine type of cytochrome P-450). Substances capable of inhibiting monooxygenase function can be identified and the in vivo occurrence of drug interactions can thus be predicted. - Dextromethorphan O-demethylation in human microsomes prepared from small human liver tissue samples is monitored as the prototype reaction. The kinetic parameters of this reaction are stable and reproducible (Km 1-5 microM, Vmax 9.1 +/- SD 4.6 nmol x mg P-1 x h-1). The reaction is inhibited by numerous drugs (quinidine, phenothiazine type neuroleptics, some dihydropyridines). Preliminary clinical results demonstrate the predictive value of this assay.

Chromatography, High Pressure Liquid↗
PubMed1984

Therapeutic approaches to the common cold in children.

In a five-day, randomized, double-blind study, the efficacy and safety of a syrup containing a combination of azatadine maleate, pseudoephedrine sulfate, and dextromethorphan hydrobromide (SCH 399 syrup) were compared with those of an expectorant containing the antihistamine diphenhydramine hydrochloride in 60 children with symptoms of the common cold and associated cough. One-half teaspoonful of assigned medication was administered three or four times daily. The severity of signs and symptoms was graded on days 0, 3, and 5. At days 3 and 5, patients treated with SCH 399 experienced a significantly greater degree of relief (P less than 0.001) than did patients treated with the expectorant product. Differences between treatment groups in overall therapeutic response, as evaluated by the physician, were statistically significant (P less than 0.001) at each visit, favoring patients treated with SCH 399. More than 75% of the patients treated with SCH 399 demonstrated an excellent therapeutic response. Tolerance to both study medications was excellent.

Antitussive Agents↗
PubMed1982

[Effects of antitussive drugs on the central respiratory mechanisms during the cough reflex].

Effects of antitussive drugs on the phrenic nerve activities during the cough reflex were investigated by means of a power spectrum analysis as a quantitative evaluation of each of the frequency band components of the phrenic nerve activities in anesthetized dogs. The efferent activities of the phrenic nerve were recorded from the central cut end of the phrenic nerve. Each fraction of the phrenic nerve activity was fractionated into bands spanning a range of 100 Hz each by a variable filter and analyzed using a program for the power spectrum analysis. The increase in power of each of the frequency band components was observed during the cough reflex induced by mechanical stimulation of the tracheal mucosa. Particularly, the power of the 2 approximately 100 Hz band components increased significantly as compared with the other frequency band components. An i.v. administration of codeine (3 mg/kg) significantly inhibited the increase in power of all frequency band components during the cough reflex. After administration of dextromethorphan (10 mg/kg, i.v.) or fominoben (8 mg/kg, i.v.), the increase in power of the 2 approximately 100 Hz band components of the phrenic nerve activity during the cough reflex was decreased significantly for 5 approximately 10 min; however, the other frequency band components were not affected. These results provide some evidence for a difference between these three antitussive drugs with respect to the mechanisms of action in the process of the central integration for the cough reflex.

Animals↗
PubMed1983

Antitussive effect of the optical isomers of mu, kappa and sigma opiate agonists/antagonists in the cat.

The optical isomer of mu and kappa opiates, when given i.v., inhibited the cough reflex in the lightly anesthetized cat, the levoisomers being, in general, 2 to 14 times more potent than the dextro-isomers. The optical isomers of the sigma agonist, SKF 10,047, did not show any antitussive activity up to near lethal or lethal doses (5 mg/kg i.v.). Naloxone (1 mg/kg i.v.) did not block or reverse the antitussive effects of (-)- and (+)-codeine but completely antagonized the effects of an ED84 of (-)-, (+)-morphine, (-)-, (+)-methadone, levomethorphan and dextromethorphan. The cough suppressant effects of the kappa opiates were partially blocked by naloxone, (+/-)-ketocyclazocine being more sensitive to the effect of naloxone than (-)-cyclazocine. (-)-SKF 10,047 at 3.0 mg/kg i.v. and the ED16 of (-)-cyclazocine did not inhibit the antitussive effect of codeine but blocked that of morphine, behaving like naloxone. (+)-SKF 10,047 and (+)-cyclazocine did not show in vivo antagonistic effect vs. codeine or morphine. The ED16 of ketocyclazocine partially antagonized codeine but not morphine. The optical isomers of opiates showed good correlation between the in vivo antitussive potencies and their in vitro inhibitory potencies against (-)-codeine binding in homogenates of the guinea-pig medulla. The data confirm the hypothesis that the cough suppressant effects of opiates are mediated by receptors which are less stereoselective and less naloxone-sensitive than the analgesic receptors. The possible involvement of mu and kappa sites as well as their interactions are discussed.

Animals↗
PubMed1995

Antipeptide antibodies targeted against specific regions of rat CYP2D1 and human CYP2D6.

Four peptides (pep23-33, pep26-38, pep283-297, and pep409-419) corresponding to unique sequences in rat cytochrome P450 (CYP) 2D1 and/or human CYP2D6 were selected for production of antipeptide antibodies. Rat liver microsomal protein was recognized by anti-serum to all four peptides in ELISAs; however, antisera against pep23-33 and pep26-36 proved not usable for any other applications. Western blots of microsomal protein from a cell line specifically expressing human CYP2D6 revealed that antisera to pep283-297 and pep409-419 recognized a single protein band of the same molecular size as CYP2D6. Antisera to pep283-297 and pep409-419 recognized a rat microsomal protein presumed to be CYP2D1, because it comigrated with human CYP2D6 and had an apparent molecular size of 52 kDa. An unknown protein of approximately 85 kDa was also recognized by pep409-419. Recognition of microsomal protein(s) by antisera to pep283-297 and pep409-419 was blocked by pep283-297 or a bovine serum albumin-pep409-419 conjugate, respectively. Antiserum to pep283-297 was used to analyze sex and strain differences in liver microsomes prepared from Sprague-Dawley, Fischer 344, and Dark Agouti male and female rats. Sprague-Dawley and Fischer 344 rats expressed similar amounts of CYP2D1, but expression in Dark Agouti rats was significantly lower. The antiserum did not detect a sexual dimorphism in any of the strains. A significant correlation between antipeptide283-297 immunoreactivity and Vmax for dextromethorphan O-demethylation existed in female rat strains; however, this relationship did not exist in male rat strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

[Cytochrome p450 IID6, its role in psychopharmacology].

Cytochrome P450 IID6 has got typical features (genetical polymorphism, competitive inhibition, saturability) which can be at the origin of pharmacokinetic modifications of molecules using it for their metabolism. In the field of pharmacology, many molecules are substrates or inhibitors of this cytochrome. They are presented. The results of a study of the dextromethorphan variation test performed before and after 28 days of clomipramine therapy with depressed patients are explained. They show a significant decreasing of the cytochrome P450 IID6 oxidation capacities between both of these times. A patient has passed from the phenotype "effective metabolizer" to the one of "poor metabolizer" with clomipramine.

Adolescent↗
PubMed1976

General pharmacological properties of a new non-opiate antitussive: zipeprol (3024 CERM). I. Action on respiratory function and acute toxicity.

1-(2-Methoxy-2-phenyl)-ethyl-4-(2-hydroxy-3-methoxy-3-phenyl)-propyl-iperazine-dihydrochloride (zipeprol, Respilene) is a substance of non-phenanthrenic chemical structure. In the cat, it antagonised cough induced by stimulation of the superior laryngeal nerve or by direct mechanical excitation of the sensitive tracheo-bronchial receptors. The efficacy of zipeprol after enteral administration made it possible both to establish good intestinal absorption and to rank it favourably in relation to several major antitussive reference products; codeine, codethyline, dextromethorphan, diphenhydramine and pentoxyverine. The activity of zipeprol was superior or equal to that of all these substances, excdept codeine. The antitussive properties appeared to be due to a central action. Other properties have been demonstrated which suggest at least a supplementary mechanism in the inhibition of cough, in addition to the central action. These consisted of slight antihistamine and anticholinergic properties, marked local-anesthetic potency and bronchospasmolytic activity. This latter property was demonstrated by the inhibition of histamine and serotonin induced bronchospasm in the guinea-pig. In vitro, using human sputum, zipeprol had a mucolytic action, shown by a decrease in sputum vis viscosity and lysis of DNA and AMPS fibrils. In the dog, at high doses, zipeprol unlike codeine, did not inhibit central stimulation of respiration by hypercapnia, in addition no modification of ventilatory dynamics or blood gases was seen. On the basis of these results, zipeprol can be considered as possessing no respiratory depressant effect even in the upper ranges of its antitussive doses.

Administration, Oral↗
PubMed1994

Hazards of nonprescription medications.

There are hundreds of nonprescription medications available to the consumer. Among these are a number that have potential for toxicity when taken in overdoses or in combination with other medications. This article addresses the pathophysiology, diagnosis, and treatment of selected over-the-counter medication intoxications including antihistamines, dextromethorphan, sympathomimetics, nutritional supplements, and herbal preparations.

Dextromethorphan↗
PubMed1994

Pharmacokinetics of desipramine coadministered with sertraline or fluoxetine.

The pharmacokinetic interactions of sertraline and fluoxetine with the tricyclic antidepressant desipramine were studied in 18 healthy male volunteers phenotyped as extensive metabolizers of dextromethorphan. Concentrations in plasma were determined after 7 days of desipramine (50 mg/day) dosing alone, during the 21 days of desipramine and selective serotonin reuptake inhibitor (SSRI) coadministration (fluoxetine, 20 mg/day; sertraline, 50 mg/day), and for 21 days of continued desipramine administration after SSRI discontinuation. Desipramine Cmax was increased 4.0-fold versus 31% and AUC0-24 was increased 4.8-fold versus 23% for fluoxetine versus sertraline, respectively, relative to baseline after 3 weeks of coadministration. Desipramine trough concentrations approached baseline within 1 week of sertraline discontinuation but remained elevated for the 3-week follow-up period after fluoxetine discontinuation. Concentrations of SSRIs and their metabolites correlated significantly with desipramine concentration changes (for fluoxetine/norfluoxetine, r = 0.94 to 0.96; p < 0.001; for sertraline/desmethylsertraline, r = 0.63; p < 0.01). Thus, sertraline had less pharmacokinetic interaction with desipramine than did fluoxetine at their respective, minimum, usually effective doses.

1-Naphthylamine↗
PubMed1993

Effect of phencyclidine on contraction of porcine coronary vessel strips.

Classic muscular contraction experiment was used to study the effect of phencyclidine (Phe) on spiral strips of porcine coronary vessels. It showed that Phe and its analogs: 1-[1-(2-thienyl)cyclohexyl] piperidine (TCP), (+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d] cyclohepten-5, 10-imine maleatel (dizocilpine maleate) and sigma receptor ligand N-allyl-N-normetazocine (SKF10047) all exhibited a concentration-dependent contraction of porcine coronary vessel strips. Phe had no effect on the electrically stimulated contraction of the spiral strips. Dextromethorphan (Dex), a Phe receptor antagonist, and haloperidol (Hal), a sigma receptor antagonist, partially antagonized and suppressed the actions of Phe in a non-competitive manner. These results suggested that Phe, TCP, dizocilpine maleate, and (+), (-)-SKF10047 cause contraction through Phe and sigma opioid receptors.

Animals↗
PubMedDate not supplied

CYP2D6, N-acetylation, and xanthine oxidase activity in cystic fibrosis.

STUDY OBJECTIVE: To determine the activity of CYP2D6, N-acetylation, and xanthine oxidase, three drug-metabolizing enzyme systems, in patients with cystic fibrosis and compare the findings with those in individuals without the disease. DESIGN: Prospective cohort study. SETTING: General pediatrics service. PATIENTS: Fifty-nine patients with cystic fibrosis and 480 healthy Caucasian volunteers. INTERVENTIONS: Enzyme activity was determined based on urinary molar metabolite ratios of caffeine and dextromethorphan probes. MEASUREMENTS AND MAIN RESULTS: The percentage of poor metabolizers of CYP2D6 in patients with cystic fibrosis was not different from that in the control group (p = 0.45). N-Acetylation activity was significantly lower in the patients (p = 0.007), but no statistically significant difference was found in xanthine oxidase activity (p = 0.12). CONCLUSION: The activity of these drug-metabolic pathways does not appear to be increased in cystic fibrosis. Whether the activity of other pathways is increased, thus providing a partial explanation for the generally increased drug clearance in this disease, remains to be determined.

Acetylation↗
PubMed1997

N-methyl-D-aspartate-mediated glutamate toxicity in the developing rabbit retina.

Extracellular levels of endogenous glutamate are relatively high in the developing rabbit retina but nonetheless appear to promote cell survival and developmental processes at concentrations considered toxic in the adult. We wished to examine the development of retinal susceptibility to glutamate toxicity as well as the protective effects of two N-methyl-D-aspartate (NMDA) antagonists, 2-amino-5-phosphono-5-valeric acid (APV) and dextromethorphan (Dex), and the nitric oxide synthase (NOS) inhibitor, NG-methyl-L-arginine (metARG). One day in vitro retinal explants of adult and neonatal rabbits were incubated with various agonists and antagonists, and stained with trypan blue to visualize necrotic cells. The density of the necrotic cells was analyzed using the Zeiss Videoplan 2. Immature neurons were approximately 10-fold less sensitive to NMDA toxicity compared to the adult. Although both NMDA antagonists and metARG provided marked protection for adult retinal neurons against glutamate toxicity, the modest susceptibility of the immature neuron was blocked only by Dex and not APV or metARG. At least two factors may contribute to the ability of the neonatal retina to survive in the presence of high levels of endogenous extracellular glutamate. First, the 10-fold developmental increase in NMDA toxicity occurs simultaneously with a 12-15-fold downregulation of extracellular glutamate, probably through the actions of maturing Muller cells. Second, the NMDA/NO excitotoxic pathway may not be active at birth since an NOS inhibitor had little effect at this stage and our previous morphological data demonstrate that NOS-containing cells are not present in their mature configuration until the second postnatal week.

2-Amino-5-phosphonovalerate↗
PubMed1997

Tryptamine: a possible endogenous substrate for CYP2D6.

The fact that CYP2D6 is not only expressed in liver but also in brain and the clinical association of this cytochrome with Parkinson's disease suggests the possibility of existence of some endogenous substrate, and among these perhaps one or more neurotransmitters could be metabolized by CYP2D6. In this study we explored such a possibility by studying the modulation of CYP2D6 activity by several neurotransmitters. Our findings confirm the occurrence of a competitive inhibition of dextromethorphan O-demethylation in the presence of tryptamine, with a Ki value of 44.6 microM. Tryptamine was metabolized in human liver microsomes by an enzyme activity with a K(m) of 3.6 +/- 0.9 microM. Such activity is NADPH dependent and is inhibited by quinidine and CYP2D6-specific substrates. The product of the reaction is tryptophol. These results suggest that tryptamine may be an endogenous substrate of CYP2D6.

Cytochrome P-450 CYP2D6↗
PubMed1997

[Clinical features of postinfectious chronic cough].

Postinfectious cough has been drawing attention as a factor involved in the etiology of chronic cough in the United States. In Japan, clinical features of postinfectious chronic cough (PICC) have not been described in detail. We investigated 22 patients with PICC diagnosed by the established criteria (Jpn. J. Allergol. 1995; 44: 1418). All patients were nonsmokers and none received ACE inhibitors. None had a history of atopy or sinus diseases. There were four men and 18 women with a median age of 65 years. These 22 patients underwent clinical examinations including chest roentgenograms, respiratory function tests, eosinophil counts in venous blood, serum IgE titers, antibody titers to Mycoplasma pneumoniae, sputum cytologic findings taken from ten patients, and histological features of bronchial biopsy specimens obtained from two patients; all findings were within normal limits. Clinical course of cough in 20 of the patients with PICC was evaluated using a cough diary. One patient did not keep a cough diary. Ten patients improved with dextromethorphan hydrobromide (D) and oxatomide (O). Three of the remaining 9 patients improved with Bakumondo-to (B) only, 4 with D+O+B, and 2 with D+O+B+ozagrel hydrochloride. The duration of cough before treatment showed a significant correlation with the time from the start of treatment to recovery (r = 0.47, p < 0.05). These results indicate that PICC tends to occur in elderly women and to improve with treatment combining with D, O, and B. We hope to establish a standard therapy for postinfectious chronic cough.

Adult↗
PubMed1998

[A pilot phase II study of combination therapy with oxatomide, an antihistamine, plus dextromethoraphan and bakumondo-to, an herbal drug, in patients with postinfectious persistent cough].

Previously, we reported the effectiveness of treatment with oxatomide (O), an antihistamine, plus dextromethorphan (D), and that of Bakumondo-to (B), an herbal drug that inhibits the activation of C-fibers, in patients with persistent coughing after upper-airway infection. In this study, we evaluated the efficacy and side effects of combination therapy (O + D + B) in patients with postinfectious persistent cough. Patients who had been coughing for more than three weeks and had a history of upper-airway infection took part in the study. None had any history of nasal disease, gastroesophageal reflux, bronchial asthma, or other chronic pulmonary disease. All patients were non-smokers, and none used angiotensin converting enzyme (ACE) inhibitors. All had normal chest roentgenograms and normal pulmonary function. The following hematological data were obtained before treatment: peripheral eosinophil counts. CRP levels, serum IgE concentrations, and titers of cold agglutinins and antibodies to Mycoplasma pneumoniae. The effects of one week of treatment with O + D + B on the severity of coughing, as estimated with a cough diary, were examined. Thirty-six patients entered the study, but only 18 with normal hematological findings who satisfied the study criteria were eligible for efficacy and side-effect analyses. Cough scores decreased significantly from 5.1 +/- 2.4 (range, 2-9) to 1.2 +/- 1.9 (range, 0-6), and the rate of cough disappearance was 50%. Two patients reported slight drowsiness. Therapy with O + D + B reduced perception of coughing as estimated with a cough diary. These results suggest that this therapy (O + D + B) may be useful in patients with postinfectious persistent cough.

Adrenergic beta-Agonists↗
PubMed1998

Mechanisms of deafferentation-induced plasticity in human motor cortex.

Deafferentation induces rapid plastic changes in the cerebral cortex, probably via unmasking of pre-existent connections. Several mechanisms may contribute, such as changes in neuronal membrane excitability, removal of local inhibition, or various forms of short- or long-term synaptic plasticity. To understand further the mechanisms involved in cortical plasticity, we tested the effects of CNS-active drugs in a plasticity model, in which forearm ischemic nerve block (INB) was combined with low-frequency repetitive transcranial magnetic stimulation (rTMS) of the deafferented human motor cortex. rTMS was used to upregulate the plastic changes caused by INB. We studied six healthy subjects. In two control sessions without drug application, INB plus rTMS increased the motor-evoked potential (MEP) size and decreased intracortical inhibition (ICI) measured with single- and paired-pulse TMS in the biceps brachii muscle proximal to INB. A single oral dose of the benzodiazepine lorazepam (2 mg) or the voltage-gated Na+ and Ca2+ channel blocker lamotrigine (300 mg) abolished these changes. The NMDA receptor blocker dextromethorphan (150 mg) suppressed the reduction in ICI but not the increase in MEP size. With sleep deprivation, used to eliminate sedation as a major factor of these drug effects, INB plus rTMS induced changes similar to that seen in the control sessions. The findings suggest that (1) the INB plus rTMS-induced increase in MEP size involves rapid removal of GABA-related cortical inhibition and short-term changes in synaptic efficacy dependent on Na+ or Ca2+ channels and that (2) the long-lasting (>60 min) reduction in ICI is related to long-term potentiation-like mechanisms given its duration and the involvement of NMDA receptor activation.

Adult↗
PubMed2000

High-throughput cytochrome P450 inhibition screening via cassette probe-dosing strategy. IV. Validation of a direct injection on-line guard cartridge extraction/tandem mass spectrometry method for simultaneous CYP3A4, 2D6 and 2E1 inhibition assessment.

A highly efficient direct injection on-line guard cartridge extraction/tandem mass spectrometry (DI-GCE/MS/MS) method has been validated for high-throughput evaluation of cytochrome P450 (CYP) 3A4, 2D6 and 2E1 inhibition potential via cassette dosing of midazolam, dextromethorphan and chlorzoxazone using human hepatic microsomes and 96-well microtiter plates. Microsomal incubations were terminated with formic acid, centrifuged, and the resulting supernatants were injected for analysis by DI-GCE/MS/MS. Due to the novel use of an extremely short C(18) guard cartridge (4 mm in length), this method exhibits several advantages such as no sample preparation, excellent on-line extraction, short run time (2.5 min), and minimized source contamination and performance deterioration. The DI-GCE/MS/MS method demonstrates acceptable accuracy and precision for the simultaneous quantification of 1'-hydroxymidazolam, dextrorphan and 6-hydroxychlorzoxazone in microsomal incubations. The inhibition potential of CYP3A4, 2D6 and 2E1 has been evaluated using their known selective inhibitors. The IC(50) values measured by the cassette dosing approach (high-throughput) are consistent with those observed by an individual dosing regimen (conventional) and are all in good agreement with the literature values. The results suggest that the cassette probe-dosing strategy may provide an in vitro approach to minimize cost while maximizing throughput of CYP inhibition evaluation of new chemical entities in support of drug discovery and development.

Calibration↗
PubMed1999

Inhibition of human cytochrome P450 isoforms in vitro by zafirlukast.

Zafirlukast is a cysteinyl leukotriene antagonist used to treat allergic and exercise-induced asthma. This in vitro study used human liver microsomes to evaluate the inhibitory activity of zafirlukast versus six human cytochrome P450 (CYP) isoforms. Zafirlukast (0-250 microM) was co-incubated with fixed concentrations of index substrates. Zafirlukast inhibited the hydroxylation of tolbutamide (CYP2C9; mean IC(50)=7.0 microM), triazolam (CYP3A; IC(50)=20.9 microM) and S-mephenytoin (CYP2C19; IC(50)=32.7 microM), and was a less potent inhibitor of phenacetin O-deethylation (CYP1A2; IC(50)=56 microM) and dextromethorphan O-demethylation (CYP2D6; IC(50)=116 microM). Zafirlukast produced negligible inhibition of CYP2E1. In vitro inhibition of CYP2C9 by zafirlukast is consistent with clinical studies showing impaired clearance of S-warfarin and enhanced anti-thrombotic effects, although the in vitro IC(50) value is higher than the usual range of clinically relevant plasma concentrations. Zafirlukast deserves further clinical study as an inhibitor of other CYP2C9 substrates such as nonsteroidal anti-inflammatory agents, tolbutamide, phenytoin and mestranol. Clinically important inhibition by zafirlukast of other CYP isoforms is not established.

Cytochrome P-450 Enzyme Inhibitors↗