Identification and weighting of the most critical "real-life" drug-drug interactions with acenocoumarol in a tertiary care hospital.

PURPOSE: The objective of this study was to identify the most clinically relevant drug-drug interactions (DDIs) at risk of affecting acenocoumarol safety in our tertiary care university hospital, a 2,000 bed institution. METHODS: We identified DDIs occurring with acenocoumarol by combining two different sources of information: a 1-year retrospective analysis of acenocoumarol prescriptions and comedications from our Computerized Physician Order Entry (CPOE) system (n = 2,439 hospitalizations) and a retrospective study of clinical pharmacology consultations involving acenocoumarol over the past 14 years (1994-2007) (n = 407). We classified these DDIs using an original risk-analysis method. A criticality index was calculated for each associated drug by multiplying three scores based on mechanism of interaction, involvement in a supratherapeutic international normalized ratio (INR) (≥ 6) and involvement in a severe bleeding. RESULTS: One hundred and twenty-six DDIs were identified and weighted. Twenty-eight drugs had a criticality index ≥ 20 and were therefore considered at high risk for interacting with acenocoumarol by increasing its effect: 75% of these drugs involved a pharmacokinetic mechanism and 14 % a pharmacodynamic mechanism. An unknown mechanism of interaction was involved in 11 % of drugs. CONCLUSION: Twenty-eight specific drugs were identified as being at high risk for interacting with acenocoumarol in our hospital using an original risk-analysis method. Most analyzed drugs interact with acenocoumarol via a pharmacokinetic mechanism. Actions such as the implementation of alerts in our CPOE system should be specifically developed for these drugs.

[Comparison of four drug interaction screening programs]. / Quel programme informatique de détection des interactions médicamenteuses néfastes?

Adverse drug events (ADE) are a major public health issue, with drug-drug interactions (DDI) being one of well-recognized causes of ADE that could be preventable by the use of DDI screening software. We compared the ability of four programs to detect clinically important DDI. We tested 62 drug pairs with and 12 drug pairs without clinically important DDI. Lexi-Interact and Epocrates were the most sensitive (95%) compared to the Compendium and Theriaque (80 and 73%, respectively). The Compendium and Theriaque also showed the lowest negative predictive value. All programs showed high specificity and positive predictive value. The qualitative assessment showed the best performances for Compendium and Lexi-Interact. The last one seems to be the best screening program, but the Compendium is in French and is freely available.

The AmpliChip CYP450 test: cytochrome P450 2D6 genotype assessment and phenotype prediction.

Polymorphisms of the cytochrome P450 2D6 (CYP2D6) gene affecting enzyme activity are involved in interindividual variability in drug efficiency/toxicity. Four phenotypic groups are found in the general population: ultra rapid (UM), extensive (EM), intermediate (IM) and poor (PM) metabolizers. The AmpliChip CYP450 test is the first genotyping array allowing simultaneous analysis of 33 CYP2D6 alleles. The main aim of this study was to evaluate the performance of this test in CYP2D6 phenotype prediction. We first verified the AmpliChip CYP450 test genotyping accuracy for five CYP2D6 alleles routinely analysed in our laboratory (alleles 3,4,5,6, x N; n=100). Results confirmed those obtained by real-time PCR. Major improvements using the array are the detection of CYP2D6 intermediate alleles and identification of the duplicated alleles. CYP2D6 phenotype was determined by assessing urinary elimination of dextromethorphan and its metabolite dextrorphan and compared to the array prediction (n=165). Although a low sensitivity of UM prediction by genotyping was observed, phenotype prediction was optimal for PM and satisfying for EM and IM.

Lack of interaction of the NMDA receptor antagonists dextromethorphan and dextrorphan with P-glycoprotein.

The anti-N-methyl-D-aspartate (NMDA) effect of dextromethorphan (DEM) seems to be mainly related to the unchanged drug rather than to its more potent metabolite dextrorphan (DOR). The aim of our study was to assess the involvement of P-glycoprotein (P-gp) and pH conditions in the transmembranal transport of these two NMDA antagonists, using a human in vitro Caco-2 cell monolayer model. Transmission electron microscopy, transepithelial electrical resistance, [(3)H]-mannitol permeability, Western blot analysis and the bidirectional transport of the positive controls, rhodamine and digoxine were used to confirm model's integrity and validity. The bidirectional transport of DEM and DOR (1 to 100microM) across the monolayers was investigated in the presence and absence of the P-gp inhibitor cyclosporine A (10microM) at two pH conditions (pH 6.8/7.7-pH 7.4/7.4) and assessed with the specific and more potent P-gp inhibitor GF120918 (4microM). Analytical quantification was achieved using high performance liquid chromatography. At a pH gradient, DEM and DOR were subject to a significant active efflux transport (Papp(B-A) > 2-3x Papp(A-B); p<0.01). However, neither the influx nor the efflux was affected by P-gp inhibitors. At physiological pH, we observed no more efflux of the drugs and no influence of the inhibitors. In conclusion, dextromethorphan and dextrorphan are not P-gp substrates. However, pH-mediated efflux mechanisms seem to be involved in limiting DEM gastrointestinal absorption. The preferential anti-NMDA central effect of DEM appears to be P-gp independent.

Development and validation of a chemical hydrolysis method for dextromethorphan and dextrophan determination in urine samples: application to the assessment of CYP2D6 activity in fibromyalgia patients.

Dextromethorphan (DEM) is a widely used probe drug for human cytochrome P450 2D6 isozyme activity assessment by measuring the ratio between DEM and its N-demethylated metabolite dextrorphan (DOR). DOR is excreted in urine mainly conjugated to glucuronic acid. Prior to quantification, DOR must be deconjugated to avoid variability caused by the polymorphic glucuronosyltransferase enzyme. A chemical hydrolysis method was optimized using a chemometric approach. Three factors (acid concentration, hydrolysis time and temperature) were selected and simultaneously varied to study their effect on conjugated DOR hydrolysis. Hydrolysis conditions that maximize DOR release without significant degradation of both DEM and DOR were chosen and results were compared to those obtained by enzymatic method using beta-glucuronidase. An HPLC method with fluorescence detection was developed for the simultaneous quantitation of DEM, DOR and levallorphan, used as an internal standard. Separation was performed on a phenyl analytical column (150 mmx4.6 mm i.d., 5 microm) with a mobile phase consisting of 18% acetonitrile and 50 mM phosphoric acid (pH 3). The overall analytical procedure was validated and showed good performances in terms of selectivity, linearity, sensitivity, precision and accuracy. Finally, this assay was used to determine DEM/DOR molar ratios in fibromyalgia patients for the purpose of determining phenotype status for the CYP2D6.

The effect of tobacco on lung cancer risk depends on CYP2D6 activity.

The genetically determined P450 CYP2D6 activity is suspected to be involved in lung carcinogenesis by activating carcinogens contained in tobacco smoke. Therefore, lung cancer risk should depend on both smoking exposure and CYP2D6 activity. The extent to which CYP2D6 activity, determined by using dextromethorphan, could modify the effect of tobacco was evaluated from a study on 128 lung cancers and 157 controls. A strong interaction was observed; the effect of tobacco on lung cancer risk rose with increasing CYP2D6 activity (P < 0.001). Increasing levels of smoking increased lung cancer risk only among smokers with the highest CYP2D6 activity, and CYP2D6 was a risk factor only among heavy smokers. Smokers with both the highest CYP2D6 activity and daily tobacco consumption were at very high risk for lung cancer. These results may explain discrepant results of previous studies on the association between CYP2D6 activity and lung cancer.

Association between lung cancer and microsomal epoxide hydrolase genotypes.

Microsomal epoxide hydrolase (mEH) is involved in the metabolism of tobacco-derived carcinogens. Polymorphisms in exons 3 and 4 of the EPHX gene have been reported to be associated with variations in mEH activity. We examined whether the predicted mEH activity modified the lung cancer risk among 150 cases and 172 controls, all French Caucasian smokers. A significant association was found between predicted mEH activity and lung cancer (P < 0.02), with a dose-effect relationship (P < 0.005). The risks associated with intermediate and high activities, compared to low activity, were 1.65 (95% CI, 0.95-2.86) and 2.66 (95% CI, 1.33-5.33), respectively. The effect of mEH activity on lung cancer risk was not significantly modified by smoking exposure, CYP1A1 genotype, or GSTM1 genotype. mEH may thus be an important genetic determinant of smoking-induced lung cancer.

High-activity microsomal epoxide hydrolase genotypes and the risk of oral, pharynx, and larynx cancers.

Human microsomal epoxide hydrolase (mEH), encoded by the EPHX1 gene, is involved in the metabolism of tobacco carcinogens. We investigated the effect of exon 3 and 4 polymorphisms of the EPHX1 gene in 121 patients with cancers of the oral cavity/pharynx, 129 patients with cancer of the larynx, and 172 non-cancer controls, all Caucasian regular smokers. The potential modifying role of previously analyzed GSTM1, GSTM3, and GSTP1 genotypes was also examined. Compared with the putative low-activity genotypes, odds ratios (ORs) associated with predicted intermediate and high mEH activity genotypes were significantly increased for oropharyngeal cancers [OR = 1.8; 95% confidence interval (CI) = 1.0-3.3; and OR = 2.1; 95% CI = 1.0-4.5, respectively; P(trend) = 0.03] and laryngeal cancers (OR = 1.7; 95% CI = 1.0-3.1; and OR = 2.4; 95% CI = 1.1-5.1, respectively; P(trend) = 0.02). Moreover, a positive interaction was found between mEH activity and GSTM3 genotype for laryngeal cancer. The combined EPHX1 high activity-associated genotype and GSTM3 (AB or BB) genotype conferred a 13.1-fold risk (95% CI = 3.5-48.4) compared with the concurrent presence of the EPHX1 low activity-associated genotype and the GSTM3 AA genotype. Thus, EPHX1 polymorphisms may be one of the factors of importance in susceptibility to smoking-related cancers of the upper aerodigestive tract.

[Behavioural and psychological symptoms of dementia (BPSD): pharmacological management]. / Prise en charge médicamenteuse des symptômes comportementaux et psychologiques liés à la démence.

BPSD affect all demented patients during their illness. They are part of the process of the disease and can be correlated to neurotransmitter dysfunctions as well as to the coping difficulties due to the patient's cognitive decline. The major consequences of BPSD are a decreased quality of life of both patient and caregivers and an increased need of professional care. Physicians should exclude precipitating factors such as intercurrent somatic, psychiatric or drug-related problems first and then proceed with behavioural or environment therapy. Introduction of a pharmacological treatment should be the last resort. This systematic review discusses the causes and consequences of BPSD and focuses on the evidence-based pharmacological approach. Only three drugs can be recommended at the present time: risperidone, olanzapine and donepezil.

[A link between sodium sensitivity and pharmacogenomics of antihypertensive drugs]. / Entre sel et gènes ou pharmaco- génomique des antihypertenseurs.

Pharmacogenomics studies the links between polymorphisms (genetic variants) and the variability of the response to some treatments in a given individual. Pharmacogenomics thus allows to explore polymorphisms that could potentially explain heterogeneous efficacy of diuretics, ACE inhibitors or angiotensin receptor blockers, beta-blockers and calcium channel blockers among populations of varied ethnical origin. There have been many studies on the relation between the efficacy of these treatments and the specific polymorphisms involved in the regulation of blood pressure. So far, no unique mutation is by itself predictive of the therapeutic response to these drugs; more elaborated polygenetic models are required so that pharmacogenomics can one day offer an individualized prescription for a complicated disease such as high blood pressure.

Development and validation of a new reversed-phase ion pairing liquid chromatographic method with fluorescence detection for penciclovir analysis in plasma and aqueous humor.

A simple, sensitive and reliable HPLC ion-pairing method with fluorescence detection, was developed for penciclovir determination in plasma and aqueous humor, with a Zorbax SB-aq C18 (100 mmx2.1 mm) column. Plasma samples were treated by solid-phase extraction with Oasis MCX (30 mg) cartridges. Ganciclovir, an antiviral drug structurally related to penciclovir, was used as internal standard (I.S.). Aqueous humor samples were directly injected into the chromatographic system. Separation was performed by a gradient elution with a mobile phase consisting of a mixture of acetonitrile and phosphate buffer 50mM containing 5mM of sodium octanesulfonate, pH 2.0, at a flow rate of 0.3 ml/min. The method was validated and showed good performances in terms of linearity, sensitivity, precision and trueness. Quantification limit was obtained at 0.05 microg/ml for aqueous humor and at 0.1 microg/ml for plasma. Finally, the proposed analytical method was used to measure penciclovir in clinical samples for a pharmacokinetic study, after oral administration of famciclovir.

Systemic allergic reaction and diffuse bone pain after exposure to a preparation of betamethasone.

Allergic reactions to corticosteroids are unexpected as they seem to contradict their pharmacodynamic action. Nevertheless, they are not infrequent, with an estimated incidence of up to 4% for cutaneous reactions. Systemic reactions are rarely reported, but their incidence might be underestimated. We report here an unusual allergic reaction to betamethasone presenting with diffuse bone pain, erythema, and bronchoconstriction, which was confirmed by a positive rechallenge in a double-blind procedure. This is the first case report of a systemic reaction to betamethasone confirmed by a positive rechallenge. An impurity in betamethasone diproprionate cannot be excluded. As this substance is frequently used in rheumatologic soft-tissue injections, it is important to recognize this potentially life-threatening side effect.

[The selection of a drug in a defined therapeutic class: the case of the HMG-CoA reductase inhibitors]. / Sélection d'un medicament dans une classe thérapeutique donnée: l'exemple des "inhibiteurs de l'HMG-CoA reductase"

The HMG-CoA reductase inhibitors have similar therapeutic targets and indications. However, their potential pharmacokinetic drug-drug interaction profile may play a significant role in their safety profile in polymedicated and polymorbid patients and can serve as a selection criterion. If their utility is clearly demonstrated in selected conditions, their safety profile remains of concern. Beside dose-related hepatic and muscular injury, other rare and important adverse drug reactions have been reported after prolonged administration such as polyneuropathy, fibrotic interstitial pulmonary disease and lupus-like syndrome. Teratogenicity has also been associated with statin therapy.

[Treating hypertension: a challenge for the general practitioner]. / Le traitement de l'hypertension artérielle: un défi pour le praticien.

Hypertension is associated with a greater risk of developing a stroke or a coronary heart disease, but remains, for the meanwhile, undertreated in a vast majority of patients. Non pharmacological interventions can reduce blood pressure and should be recommended to every patient suffering from hypertension. Nevertheless, a drug therapy must often be introduced. The threshold at which a treatment should be started depends mostly on the cardiovascular risk of each patient and the benefit of antihypertensive drug therapy depends primarily on the reduction of the blood pressure itself.

N-acetyltransferase NAT1 and NAT2 genotypes and lung cancer risk.

Acetyltransferases, encoded by the NAT1 and NAT2 genes, are involved in the activation/inactivation reactions of numerous xenobiotics, including tobacco-derived aromatic amine carcinogens. Several allelic variants of NAT1 and NAT2, which cause variations in acetylation capacity, have been detected. The NAT2 slow acetylator phenotype/genotype has been inconsistently associated with lung cancer and, to date, the role of NAT1 polymorphism in lung cancer has not been reported. The effect of NAT1 and NAT2 genetic polymorphisms on individual lung cancer risk was evaluated among 150 lung cancer patients and 172 control individuals, all French Caucasian smokers. The NAT1 alleles (*3, *4, *10, *11, *14, and *15) and the NAT2 alleles (*4, *5, *6, *7) were differentiated by polymerase chain reaction-based restriction fragment length polymorphism methods using DNA extracted from peripheral white blood cells. Genotypes were classified according to current knowledge of the functional activity of the variant alleles. The NAT1*10 and NAT1*11 alleles were considered as rapid alleles, the NAT1*4 and the NAT1*3 as normal alleles and NAT1*14 and NAT1*15 as slow-acetylation alleles. Logistic regression analyses were performed taking into account the age, sex, smoking and occupational exposures. A significant association was observed between lung cancer and NAT1 genotypes (P(homogeneity) < 0.02) with a gene dose effect (P(trend) < 0.01); compared with homozygous rapid acetylators, the lung cancer risk was 4.0 (95% confidence interval 0.8-19.6) for heterozygous rapid acetylators, 6.4 (95% confidence interval 1.4-30.5) for homozygous normal acetylators and 11.7 (95% confidence interval 1.3-106.5) for heterozygous slow acetylators. None of the individuals were homozygous slow acetylators. Similar results were obtained whatever the adjustment considered. No significant association was found between NAT2 genotype and lung cancer. The NAT1 polymorphism may thus be an important modifier of individual susceptibility to smoking-induced lung cancer.

Role of glutathione S-transferase GSTM1, GSTM3, GSTP1 and GSTT1 genotypes in modulating susceptibility to smoking-related lung cancer.

Glutathione S-transferases GSTM1, GSTM3, GSTP1 and GSTT1 are involved in the detoxification of active metabolites of several carcinogens in tobacco smoke. We studied the potential role of GSTM3 and GSTP1 gene polymorphisms either separately, or in combination with GSTM1 and GSTT1 gene polymorphisms, in susceptibility to lung cancer using peripheral blood DNA from 150 lung cancer patients and 172 control individuals, all regular smokers. The frequencies of GSTM3, AA, AB and BB genotypes were 70.7%, 24.0% and 5.3% in cases and 72.7%, 24.4% and 2.9% in control individuals respectively. The frequencies of GSTP1, AA, AG and GG genotypes were 44.7%, 44.0% and 11.3% in cases and 50.0%, 37.2% and 12.8% in control individuals respectively. When studied separately, neither GSTM3 nor GSTP1 genotypes contributed significantly to the risk of lung cancer. Although failing to reach statistical significance, the combined GSTM3 AA and GSTP1 (AG or GG) genotype conferred a nearly threefold risk when the GSTM1 gene was concurrently lacking (odds ratio 2.9, 95% confidence interval 0.7-12.1). Significant interactions were observed between pack-years of smoking and the combined GSTM3 AA and GSTP1 (AG or GG) genotype, or the combined GSTM3 AA, GSTP1 (AG or GG) and GSTM1 null genotype. The combination of these three a priori at risk genotypes conferred an increased risk of lung cancer among smokers with a history of at least 35 pack-years (odds ratio 2.7, 95% confidence interval 1.2-6.0), but not in lighter smokers, probable because of the lower average number of pack-years of smoking found among control individuals with this genotype combination.

An additional defective allele, CYP2C19*5, contributes to the S-mephenytoin poor metabolizer phenotype in Caucasians.

The metabolism of the anticonvulsant drug mephenytoin exhibits a genetic polymorphism in humans. This polymorphism exhibits marked racial heterogeneity, with the poor metabolizer PM phenotype representing 13-23% of oriental populations, but only 2-5% of Caucasian populations. Two defective CYP2C19 alleles (CYP2C19*2 and CYP2C19*3) have been described, which account for more than 99% of Oriental poor metabolizer alleles but only approximately 87% of Caucasian poor metabolizer alleles. Therefore, additional defects presumably contribute to the poor metabolizer in Caucasians. Recent studies have found a third mutation CYP2C19*4, which accounts for approximately 3% of Caucasian poor metabolizer alleles. A fourth rare mutation (CYP2C19*5A) (C99,A991,Ile331;C1297T,Arg433-->Trp) resulting in an Arg433 to Trp substitution in the heme-binding region has been reported in a single Chinese poor metaboliser outlier belonging to the Bai ethnic group. The present study identifies a second variant allele CYP2C19*5B (C99-->T; A991-->G, Ile331-->Val; C1297-T, Arg433-->Trp in one of 37 Caucasian poor metabolizers. The frequency of the CYP2C19*5 alleles is low in Chinese (approximately 0.25% in the Bai ethnic group) and Caucasians (< 0.9%). However, these alleles contribute to the poor metabolizer phenotype in both ethnic groups and increases the sensitivity of the genetic tests for identifying defective alleles to approximately 100% in Chinese poor metabolizers and 92% in Caucasian poor metabolizers genotyped in our laboratory. The Arg433 to Trp mutation in the heme-binding region essentially abolishes activity of recombinant CYP2C19*5A toward S-mephenytoin and tolbutamide, which is consistent with the conclusion that CYP2C19*5 represents poor metabolizer alleles.

Serum concentrations and effects of (+/-)-nicardipine compared with nifedipine in a population of healthy subjects.

The dihydropyridine calcium antagonist (+/-)-nicardipine shares some of the pharmacologic properties of the dihydropyridine prototype nifedipine. To compare them, serum concentrations and cardiovascular effects of 10 mg nifedipine and 20 mg (+/-)-nicardipine were evaluated at 1, 2, and 3 hours after oral intake in a randomized, crossover, single-blind study involving 79 healthy volunteers. (+/-)-Nicardipine serum concentrations were much lower than those of nifedipine, indicating a greater hepatic first-pass metabolism of (+/-)-nicardipine. There was a significant correlation between serum concentrations of both drugs. The frequency distributions of nifedipine and (+/-)-nicardipine AUC (0-3), heart rate increase, and mean arterial pressure decrease showed no bimodality. This does not confirm the proposed polymorphism of nifedipine oxidation. Concentration-effect plots indicate that (+/-)-nicardipine is more potent than nifedipine but shows comparable efficacy in blood pressure reduction.

Dextromethorphan O-demethylation in liver microsomes as a prototype reaction to monitor cytochrome P-450 db1 activity.

Liver dextromethorphan O-demethylation to dextrorphan is associated with the debrisoquin type of oxidation phenotype in humans. We studied dextromethorphan oxidation in vitro using human liver microsomes to investigate the kinetics of the polymorphic monooxygenase (cytochrome P-450 db1) and factors that may influence its activity. In microsomal preparations from six extensive metabolizers the reaction parameters were: Michaelis-Menten constant = 3.4 +/- SD 1.0 mumol/L and maximum rate of metabolism = 10.2 +/- 5.3 nmol x mg P-1 x hr-1, vs 48 mumol/L and 2.2 nmol x mg P-1 x hr-1, respectively in microsomes prepared from the liver of one poor metabolizer. The reaction was inhibited by nonspecific monooxygenase inhibitors such as SKF 525-A (Ki = 100 nmol/L) and cimetidine (Ki = 40 mumol/L), by known substrates of the polymorphic isozyme such as [+]-bufuralol (Ki = 7.5 mumol/L), debrisoquin (Ki = 25 mumol/L), and sparteine (Ki = 45 mumol/L), and by the selective cytochrome P-450 db1 inhibitor quinidine (Ki = 15 nmol/L). This assay permits in vitro screening for candidate substrates or inhibitors of the polymorphic isozyme.

Central analgesic effects of desipramine, fluvoxamine, and moclobemide after single oral dosing: a study in healthy volunteers.

The antinociceptive effect of three antidepressants with different postulated modes of action, 75 mg desipramine, 225 mg fluvoxamine, and 450 mg moclobemide, was evaluated after single oral dosing in a randomized, double-blind, placebo-controlled crossover study in 10 healthy volunteers. Experimental pain thresholds (polysynaptic R-III reflex and subjective pain rating) were monitored over 23 hours. Compared with placebo, all drugs induced significant subjective pain threshold increases (maximal increase: desipramine, +20%; fluvoxamine, +17%; moclobemide, +13%). However, only desipramine (maximal increase, +25%) and moclobemide (maximal increase, +14%) displayed a significative effect on R-III threshold. Antidepressants thus exert an antinociceptive effect after a single oral dose. The level of their action apparently relies on the postulated mode of action.