The rationale of retinal endovascular fibrinolysis in the treatment of retinal vein occlusion : from experimental data to clinical application.

PURPOSE: : We describe a retinal endovascular fibrinolysis technique to directly reperfuse experimentally occluded retinal veins using a simple micropipette. METHODS: : Retinal vein occlusion was photochemically induced in 12 eyes of 12 minipigs: after intravenous injection of 10% fluorescein (1-mL bolus), the targeted retinal vein segment was exposed to thrombin (50 units) and to Argon laser (100-200 mW) through a pars plana approach. A beveled micropipette with a 30-μm-diameter sharp edge was used for micropuncture of the occluded vein and endovascular microinjection of tissue plasminogen activator (50 μg/mL) in 11 eyes. In one control eye, balanced salt solution was injected. The lesion site was examined histologically. RESULTS: : Retinal vein occlusion was achieved in all cases. Endovascular microinjection of tissue plasminogen activator or balanced salt solution led to reperfusion of the occluded retinal vein in all cases. Indicative of successful reperfusion were the following: continuous endovascular flow, unaffected collateral circulation, no optic disk ischemia, and no venous wall bleeding. However, balanced salt solution injection was accompanied by thrombus formation at the punctured site, whereas no thrombus was observed with tissue plasminogen activator injection. CONCLUSION: : Retinal endovascular fibrinolysis constitutes an efficient method of micropuncture and reperfusion of an experimentally occluded retinal vein. Thrombus formation at the punctured site can be prevented by injection of tissue plasminogen activator.

Exhaustion of bacteria-specific CD4 T cells and microbial translocation in common variable immunodeficiency disorders.

In the present study, we have investigated the functional profile of CD4 T cells from patients with common variable immunodeficiency (CVID), including production of cytokines and proliferation in response to bacteria and virus-derived antigens. We show that the functional impairment of CD4 T cells, including the reduced capacity to proliferate and to produce IFN-γ and IL-2, was restricted to bacteria-specific and not virus-specific CD4 T cells. High levels of endotoxins were found in the plasma of patients with CVID, suggesting that CD4 T cell dysfunction might be caused by bacterial translocation. Of note, endotoxemia was associated with significantly higher expression of programmed death 1 (PD-1) on CD4 T cells. The blockade of the PD-1-PD-L1/2 axis in vitro restored CD4 T cell proliferation capacity, thus indicating that PD-1 signaling negatively regulates CD4 T cell functions. Finally, we showed that intravenous immunoglobulin G (IVIG) treatment significantly reduced endotoxemia and the percentage of PD-1(+) CD4 T cells, and restored bacteria-specific CD4 T cell cytokine production and proliferation. In conclusion, the present study demonstrates that the CD4 T cell exhaustion and functional impairment observed in CVID patients is associated with bacterial translocation and that IVIG treatment resolves bacterial translocation and restores CD4 T cell functions.

Fracture risk and zoledronic acid therapy in men with osteoporosis.

BACKGROUND: Fractures in men are a major health issue, and data on the antifracture efficacy of therapies for osteoporosis in men are limited. We studied the effect of zoledronic acid on fracture risk among men with osteoporosis. METHODS: In this multicenter, double-blind, placebo-controlled trial, we randomly assigned 1199 men with primary or hypogonadism-associated osteoporosis who were 50 to 85 years of age to receive an intravenous infusion of zoledronic acid (5 mg) or placebo at baseline and at 12 months. Participants received daily calcium and vitamin D supplementation. The primary end point was the proportion of participants with one or more new morphometric vertebral fractures over a period of 24 months. RESULTS: The rate of any new morphometric vertebral fracture was 1.6% in the zoledronic acid group and 4.9% in the placebo group over the 24-month period, representing a 67% risk reduction with zoledronic acid (relative risk, 0.33; 95% confidence interval, 0.16 to 0.70; P=0.002). As compared with men who received placebo, men who received zoledronic acid had fewer moderate-to-severe vertebral fractures (P=0.03) and less height loss (P=0.002). Fewer participants who received zoledronic acid had clinical vertebral or nonvertebral fractures, although this difference did not reach significance because of the small number of fractures. Bone mineral density was higher and bone-turnover markers were lower in the men who received zoledronic acid (P<0.05 for both comparisons). Results were similar in men with low serum levels of total testosterone. The zoledronic acid and placebo groups did not differ significantly with respect to the incidence of death (2.6% and 2.9%, respectively) or serious adverse events (25.3% and 25.2%). CONCLUSIONS: Zoledronic acid treatment was associated with a significantly reduced risk of vertebral fracture among men with osteoporosis. (Funded by Novartis Pharma; ClinicalTrials.gov number, NCT00439647.).

Traitement pharmacologique de l'état de mal réfractaire [Drug treatment of refractory status epilepticus]

Status epilepticus (SE) refractory to benzodiazepines and other antiepileptic agents is managed with intravenous anesthetic compounds, such as thiopental, propofol or midazolam. These drugs display quite different pharmacodynamic and pharmacokinetic properties, but have not been prospectively compared to date. Their use is clearly advocated for the treatment of generalized convulsive SE, whereas partial-complex, or absence SE are generally managed less aggressively, in consideration of their better prognosis. The most important aspect seems to be related to the correct use of these anesthetics in the right context, rather than the choice of one specific compound. An electroencephalographic burst-suppression should be targeted for about 24hour, before progressive weaning of the dosage under EEG monitoring. If this approach proves unsuccessful, the use of other drugs, including inhalational anesthetics, has been described.

Genotype 3 is associated with accelerated fibrosis progression in chronic hepatitis C.

BACKGROUND/AIMS: While several risk factors for the histological progression of chronic hepatitis C have been identified, the contribution of HCV genotypes to liver fibrosis evolution remains controversial. The aim of this study was to assess independent predictors for fibrosis progression. METHODS: We identified 1189 patients from the Swiss Hepatitis C Cohort database with at least one biopsy prior to antiviral treatment and assessable date of infection. Stage-constant fibrosis progression rate was assessed using the ratio of fibrosis Metavir score to duration of infection. Stage-specific fibrosis progression rates were obtained using a Markov model. Risk factors were assessed by univariate and multivariate regression models. RESULTS: Independent risk factors for accelerated stage-constant fibrosis progression (>0.083 fibrosis units/year) included male sex (OR=1.60, [95% CI 1.21-2.12], P<0.001), age at infection (OR=1.08, [1.06-1.09], P<0.001), histological activity (OR=2.03, [1.54-2.68], P<0.001) and genotype 3 (OR=1.89, [1.37-2.61], P<0.001). Slower progression rates were observed in patients infected by blood transfusion (P=0.02) and invasive procedures or needle stick (P=0.03), compared to those infected by intravenous drug use. Maximum likelihood estimates (95% CI) of stage-specific progression rates (fibrosis units/year) for genotype 3 versus the other genotypes were: F0-->F1: 0.126 (0.106-0.145) versus 0.091 (0.083-0.100), F1-->F2: 0.099 (0.080-0.117) versus 0.065 (0.058-0.073), F2-->F3: 0.077 (0.058-0.096) versus 0.068 (0.057-0.080) and F3-->F4: 0.171 (0.106-0.236) versus 0.112 (0.083-0.142, overall P<0.001). CONCLUSIONS: This study shows a significant association of genotype 3 with accelerated fibrosis using both stage-constant and stage-specific estimates of fibrosis progression rates. This observation may have important consequences for the management of patients infected with this genotype.

Estimating national-level syringe availability to injecting drug users and injection coverage: Switzerland, 1996-2006.

BACKGROUND: Measuring syringe availability and coverage is essential in the assessment of HIV/AIDS risk reduction policies. Estimates of syringe availability and coverage were produced for the years 1996 and 2006, based on all relevant available national-level aggregated data from published sources. METHODS: We defined availability as the total monthly number of syringes provided by harm reduction system divided by the estimated number of injecting drug users (IDU), and defined coverage as the proportion of injections performed with a new syringe, at national level (total supply over total demand). Estimates of supply of syringes were derived from the national monitoring system, including needle and syringe programmes (NSP), pharmacies, and medically prescribed heroin programmes. Estimates of syringe demand were based on the number of injections performed by IDU derived from surveys of low threshold facilities for drug users (LTF) with NSP combined with the number of IDU. This number was estimated by two methods combining estimates of heroin users (multiple estimation method) and (a) the number of IDU in methadone treatment (MT) (non-injectors) or (b) the proportion of injectors amongst LTF attendees. Central estimates and ranges were obtained for availability and coverage. RESULTS: The estimated number of IDU decreased markedly according to both methods. The MT-based method (from 14,818 to 4809) showed a much greater decrease and smaller size of the IDU population compared to the LTF-based method (from 24,510 to 12,320). Availability and coverage estimates are higher with the MT-based method. For 1996, central estimates of syringe availability were 30.5 and 18.4 per IDU per month; for 2006, they were 76.5 and 29.9. There were 4 central estimates of coverage. For 1996 they ranged from 24.3% to 43.3%, and for 2006, from 50.5% to 134.3%. CONCLUSION: Although 2006 estimates overlap 1996 estimates, the results suggest a shift to improved syringe availability and coverage over time.

Imagerie cardiaque non invasive: apport spécifique en clinique des nouvelles modalités (I). Evaluation morphologique [Cardiac imaging: specific clinical role of newly developed non invasive techniques. Part 1: Morphological evaluation].

Echocardiography is the preferred initial test to assess cardiac morphology and ventricular function. Cardiac MRI enables an optimal visualisation of heart muscle without contrast injection, and precise measurement of the ventricular volumes and systolic function. It is therefore an ideal test for patients with poor echocardiographic windows or for the specific evaluation of right heart chambers. Heart CT also remarkably images heart muscle and precisely measures ventricular systolic function after intravenous injection of iodinated contrast. Coronary CT may also, in selected cases, avoid the need for diagnostic coronary angiography. Although very accurate, these imaging modalities are expensive and may be contra-indicated for a particular patient. Their use in clinical practice has to follow the accepted guidelines.

Clinical and hormonal effects of the new angiotensin II receptor antagonist LRB081.

The renin-angiotensin system is a major contributor to the pathophysiology of cardiovascular diseases such as congestive heart failure and hypertension. Antagonizing angiotensin (Ang) II at the receptor site may produce fewer side effects than inhibition of the promiscuous converting enzyme. The present study was designed to assess in healthy human subjects the effect of LRB081, a new orally active AT1-receptor antagonist, on the pressor action of exogenous Ang II. At the same time, plasma hormones and drug levels were monitored. At 1-week intervals and in a double-blind randomized fashion, 8 male volunteers received three doses of LRB081 (10, 40, and 80 mg) and placebo. Blood pressure (BP) was measured at a finger by photoplethysmograph. The peak BP response to intravenous injection of a standard dose of Ang II was determined before and for < or = 24 h after administration of an oral dose of LRB081 or placebo. After drug administration, the blood BP response to Ang II was expressed in percent of the response before drug administration. At the same time, plasma renin activity (PRA), Ang II, aldosterone, catecholamine (radioassays), and drug levels (by high-performance liquid chromatography) were monitored. After LRB081 administration, a dose dependent inhibition of the BP response to Ang II was observed. Maximal inhibition of the systolic BP response was 54 +/- 3 (mean +/- SEM), 63 +/- 2, and 93 +/- 1% with 10, 40, and 80 mg LRB081, respectively. The time to peak was 3 h for 6 subjects and 4 and 6 h for 2 others. Preliminary plasma half-life (t1/2) was calculated at 2 h. With the highest dose, the inhibition remained significant for 24 h (31 +/- 5%, p < 0.05). Maximal BP-blocking effect and maximal plasma drug level coincided, suggesting that the unmetabolized LRB081 is responsible for the antagonistic effect. PRA and Ang II increased dose dependently after LRB081 intake. Aldosterone, epinephrine, and norepinephrine concentrations remained unchanged. No clinically significant adverse reaction was observed during the study. LRB081 is a well-tolerated, orally active, potent, and long-acting Ang II receptor antagonist. Unlike in the case of losartan, no active metabolite of LRB081 has been shown to be responsible for the main effects.

Splenic hypereosinophilia in anaphylaxis-related death: different assessments depending on different types of allergens?

The aim of this study was to evaluate splenic eosinophil and mast cell accumulation using pagoda red stain in a series of anaphylaxis-related deaths that underwent medico-legal investigations. Our goal was to assess whether fatal reactions to insect stings, intramuscularly administered antibiotics and intravenously injected contrast media are responsible for specific patterns of eosinophil and mast cell accumulation. Two study groups were prospectively formed, an anaphylaxis-related death group and a control group. Autopsy, histology (haematoxylin-eosin stain, pagoda red stain and immunohistochemistry using anti-tryptase antibodies), toxicology and postmortem biochemistry (beta-tryptase, total IgE and specific IgE) were performed in all cases. All tested parameters (spleen weight, beta-tryptase and total IgE levels as well as eosinophil, mast cell and degranulated mast cell numbers in the spleen) were significantly higher in the anaphylaxis-related death group. No statistically significant differences were observed among the various groups (intramuscular antibiotic injection, intravenous contrast medium administration and stinging insects) in any combination, suggesting that mast cell and eosinophil accumulation in the spleen during anaphylaxis does not have any specific pattern related to the triggering allergen. Despite a lower sensitivity than immunohistochemical staining in discriminating eosinophil and mast cells, pagoda red stain allowed these cells to be identified and could therefore be proposed as a low-cost, first-line diagnostic procedure in those situations where immunohistochemistry is not systematically performed or cannot be carried out.

The role of C-Jun N-terminal kinase in a mouse model of intracerebral hemorrhage

Background: Intracerebral hemorrhage (ICH) is a subtype of stroke characterized by a haematoma within the brain parenchyma resulting from blood vessel rupture and with a poor outcome. In ICH, the blood entry into the brain triggers toxicity resulting in a substantial loss of neurons and an inflammatory response. At the same time, blood-brain barrier (BBB) disruption increases water content (edema) leading to growing intracranial pressure, which in turn worsens neurological outcome. Although the clinical presentation is similar in ischemic and hemorrhagic stroke, the treatment is different and the stroke type needs to be determined beforehand by imaging which delays the therapy. C-Jun N-terminal kinases (JNKs) are a family of kinases activated in response to stress stimuli and involved in several pathways such as apoptosis. Specific inhibition of JNK by a TAT-coupled peptide (XG-102) mediates strong neuroprotection in several models of ischemic stroke in rodents. Recently, we have observed that the JNK pathway is also activated in a mouse model of ICH, raising the question of the efficacy of XG-102 in this model. Method: ICH was induced in the mouse by intrastriatal injection of bacterial collagenase (0,1 U). Three hours after surgery, animals received an intravenous injection of 100 mg/kg of XG-102. The neurological outcome was assessed everyday until sacrifice using a score (from 0 to 9) based on 3 behavioral tests performed daily until sacrifice. Then, mice were sacrificed at 6 h, 24 h, 48 h, and 5d after ICH and histological studies performed. Results: The first 24 h after surgery are critical in our ICH mice model, and we have observed that XG-102 significantly improves neurological outcome at this time point (mean score: 1,8 + 1.4 for treated group versus 3,4+ 1.8 for control group, P<0.01). Analysis of the lesion volume revealed a significant decrease of the lesion area in the treated group at 48h (29+ 11mm3 in the treated group versus 39+ 5mm3 in the control group, P=0.04). XG-102 mainly inhibits the edema component of the lesion. Indeed, a significant inhibition Journal of Cerebral Blood Flow & Metabolism (2009) 29, S490-S493 & 2009 ISCBFM All rights reserved 0271-678X/09 $32.00 www.jcbfm.com of the brain swelling was observed in treated animals at 48h (14%+ 13% versus 26+ 9% in the control group, P=0.04) and 5d (_0.3%+ 4.5%versus 5.1+ 3.6%in the control group, P=0.01). Conclusions: Inhibition of the JNK pathway by XG- 102 appears to lead to several beneficial effects. We can show here a significant inhibition of the cerebral edema in the ICH model providing a further beneficial effect of the XG-102 treatment, in addition to the neuroprotection previously described in the ischemic model. This result is of interest because currently, clinical treatment for brain edema is limited. Importantly, the beneficial effects observed with XG-102 in models of both stroke types open the possibility to rapidly treat stroke patients before identifying the stroke subtype by imaging. This will save time which is precious for stroke outcome.

Treatment and outcomes of acute basilar artery occlusion in the Basilar Artery International Cooperation Study (BASICS): a prospective registry study.

BACKGROUND: Treatment strategies for acute basilar artery occlusion (BAO) are based on case series and data that have been extrapolated from stroke intervention trials in other cerebrovascular territories, and information on the efficacy of different treatments in unselected patients with BAO is scarce. We therefore assessed outcomes and differences in treatment response after BAO. METHODS: The Basilar Artery International Cooperation Study (BASICS) is a prospective, observational registry of consecutive patients who presented with an acute symptomatic and radiologically confirmed BAO between November 1, 2002, and October 1, 2007. Stroke severity at time of treatment was dichotomised as severe (coma, locked-in state, or tetraplegia) or mild to moderate (any deficit that was less than severe). Outcome was assessed at 1 month. Poor outcome was defined as a modified Rankin scale score of 4 or 5, or death. Patients were divided into three groups according to the treatment they received: antithrombotic treatment only (AT), which comprised antiplatelet drugs or systemic anticoagulation; primary intravenous thrombolysis (IVT), including subsequent intra-arterial thrombolysis; or intra-arterial therapy (IAT), which comprised thrombolysis, mechanical thrombectomy, stenting, or a combination of these approaches. Risk ratios (RR) for treatment effects were adjusted for age, the severity of neurological deficits at the time of treatment, time to treatment, prodromal minor stroke, location of the occlusion, and diabetes. FINDINGS: 619 patients were entered in the registry. 27 patients were excluded from the analyses because they did not receive AT, IVT, or IAT, and all had a poor outcome. Of the 592 patients who were analysed, 183 were treated with only AT, 121 with IVT, and 288 with IAT. Overall, 402 (68%) of the analysed patients had a poor outcome. No statistically significant superiority was found for any treatment strategy. Compared with outcome after AT, patients with a mild-to-moderate deficit (n=245) had about the same risk of poor outcome after IVT (adjusted RR 0.94, 95% CI 0.60-1.45) or after IAT (adjusted RR 1.29, 0.97-1.72) but had a worse outcome after IAT compared with IVT (adjusted RR 1.49, 1.00-2.23). Compared with AT, patients with a severe deficit (n=347) had a lower risk of poor outcome after IVT (adjusted RR 0.88, 0.76-1.01) or IAT (adjusted RR 0.94, 0.86-1.02), whereas outcomes were similar after treatment with IAT or IVT (adjusted RR 1.06, 0.91-1.22). INTERPRETATION: Most patients in the BASICS registry received IAT. Our results do not support unequivocal superiority of IAT over IVT, and the efficacy of IAT versus IVT in patients with an acute BAO needs to be assessed in a randomised controlled trial. FUNDING: Department of Neurology, University Medical Center Utrecht.

Recanalization and Collaterals Predict Outcome in Proximal MCA Occlusion, but neither Penumbra nor Core of Stroke

Data on new predictors of outcome include penumbra core or collaterals.Objective: To test the predictive value of recanalization, collaterals, penumbra and core of ischemia for functional outcome in a large group of patients with MCA occlusion. Method: Consecutive events included prospectively in the Acute Stroke Registry and Analysis of Lausanne from April 2002 to April 2009 with an acute stroke due to proximal MCA occlusion (M1) were considered for analysis. Acute CTA were reviewed to grade the collaterals (dichotomized in poor __50% or good _50% compared to the normal side) and localization of M1 occlusion (proximal or mid-distal). Acute CTP were reviewed and reconstructed to determine penumbra, core and stroke index (penumbra/penumbra_core) of brain ischemia. Good outcome was defined by mRS 0-2 at 3 months.Results: Among 242 events (115 male, mean NIHSS 18.1, SD 5.8, mean age 66, SD 15), 42% were treated with intravenous thrombolysis, and 3% with intraarterial thrombolysis. Collateral status was rated as poor in 53% of events and proximal M1 occlusion was present in 64%. Recanalization determined at 24 hours with CTA was complete in 26% events and partial/absent in 54%.CTP was available for 212 events. Mean penumbra was 88.6 cm3 (median 84.4, SD 53.8), mean core was 54.1 cm3 (median 46.2, SD 45.7) and stroke index was 64% (median 68%, SD 25%). Good outcome was observed in 87 events (36%) and was associated in multivariate logistic regression with thrombolysis (p_0.02, OR_2.5, 95% CI 1.2-5.4), recanalization (p_0.001, OR_4.1, 95% CI 1.9-8.9), lower NIHSS (p_0.001, OR_0.84, 95% CI 0.78-0.91), male gender (p_0.01, OR_2.8, 95% CI 1.3-5.9), mRS prior to stroke (p_0.02, OR_0.5, 95% CI 0.28-0.9) and good collateral status (p_0.005, OR_3, 95% CI 1.4-6.4). Nor penumbra, nor core, nor stroke index were significant in the multivariate model, even if an association was present in the univariate model between good functional outcome and penumbra (p_0.004, OR_1.008, 95% CI 1.003-1.01), core (p_0.001, OR_0.98, 95% CI 0.976-0.99) and strokeindex (p_0.001, OR_16.7, 95% CI 4.6 59.9).Conclusion: MCA recanalization is the best predictor for good functional outcome, followed by collateral status. CTP data did not predict the functional outcome in our large group of M1 occlusion. Author Disclosures: C. Odier: None. P. Michel: Research Grant; Significant; Paion, Lundbeck. Speakers; Modest; Boehringer-Ingelheim. Consultant/Advisory Board; Modest; Boehringer- Ingelheim. Consultant/Advisory Board; Significant; Servier, Lundbeck.

Time of injection determines the effect of alpha-MSH antiserum on DA neurons in psychological stress

Male rats were subjected to "psychological stress" which consisted in 10 sec footshock on the first day followed 24 hr later by a 10 sec stay in the experimental chamber without shock. Intravenous antiserum against alpha-MSH markedly changed the functional state of mesencephalic and hypothalamic DA neurons (assessed by histochemical microfluorimetry) when administered before the second session but not when given before the first session. These observations reveal an interesting parallelism in the temporal characteristics of the effects of alpha-MSH on avoidance behavior and central DA systems.

Safety, pharmacokinetics, and preliminary clinical activity of inotuzumab ozogamicin, a novel immunoconjugate for the treatment of B-cell non-Hodgkin's lymphoma: results of a phase I study.

PURPOSE Inotuzumab ozogamicin (CMC-544) is an antibody-targeted chemotherapy agent composed of a humanized anti-CD22 antibody conjugated to calicheamicin, a potent cytotoxic agent. This was a phase I study to determine the maximum-tolerated dose (MTD), safety, and preliminary efficacy of inotuzumab ozogamicin in an expanded MTD cohort of patients with relapsed or refractory CD22(+) B-cell non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS Inotuzumab ozogamicin was administered intravenously as a single agent once every 3 or 4 weeks at doses ranging from 0.4 to 2.4 mg/m(2). Outcomes included MTD, safety, pharmacokinetics, response, progression-free survival (PFS), and overall survival. Results Seventy-nine patients were enrolled. The MTD was determined to be 1.8 mg/m(2). Common adverse events at the MTD were thrombocytopenia (90%), asthenia (67%), and nausea and neutropenia (51% each). The objective response rate at the end of treatment was 39% for the 79 enrolled patients, 68% for all patients with follicular NHL treated at the MTD, and 15% for all patients with diffuse large B-cell lymphoma treated at the MTD. Median PFS was 317 days (approximately 10.4 months) and 49 days for patients with follicular NHL and diffuse large B-cell lymphoma, respectively. CONCLUSION Inotuzumab ozogamicin has demonstrated efficacy against CD22(+) B-cell NHL, with reversible thrombocytopenia as the main toxicity.

Interindividual variability of the clinical pharmacokinetics of methadone: implications for the treatment of opioid dependence

Methadone is widely used for the treatment of opioid dependence. Although in most countries the drug is administered as a racemic mixture of (R)- and (S)- methadone, (R)-methadone accounts for most, if not all, of the opioid effects. Methadone can be detected in the blood 15-45 minutes after oral administration, with peak plasma concentration at 2.5-4 hours. Methadone has a mean bioavailability of around 75% (range 36-100%). Methadone is highly bound to plasma proteins, in particular to alpha(1)-acid glycoprotein. Its mean free fraction is around 13%, with a 4-fold interindividual variation. Its volume of distribution is about 4 L/kg (range 2-13 L/kg). The elimination of methadone is mediated by biotransformation, followed by renal and faecal excretion. Total body clearance is about 0.095 L/min, with wide interindividual variation (range 0.02-2 L/min). Plasma concentrations of methadone decrease in a biexponential manner, with a mean value of around 22 hours (range 5-130 hours) for elimination half-life. For the active (R)-enantiomer, mean values of around 40 hours have been determined. Cytochrome P450 (CYP) 3A4 and to a lesser extent 2D6 are probably the main isoforms involved in methadone metabolism. Rifampicin (rifampin), phenobarbital, phenytoin, carbamazepine, nevirapine, and efavirenz decrease methadone blood concentrations, probably by induction of CYP3A4 activity, which can result in severe withdrawal symptoms. Inhibitors of CYP3A4, such as fluconazole, and of CYP2D6, such as paroxetine, increase methadone blood concentrations. There is an up to 17-fold interindividual variation of methadone blood concentration for a given dosage, and interindividual variability of CYP enzymes accounts for a large part of this variation. Since methadone probably also displays large interindividual variability in its pharmacodynamics, methadone treatment must be individually adapted to each patient. Because of the high morbidity and mortality associated with opioid dependence, it is of major importance that methadone is used at an effective dosage in maintenance treatment: at least 60 mg/day, but typically 80-100 mg/day. Recent studies also show that a subset of patients might benefit from methadone dosages larger than 100 mg/day, many of them because of high clearance. In clinical management, medical evaluation of objective signs and subjective symptoms is sufficient for dosage titration in most patients. However, therapeutic drug monitoring can be useful in particular situations. In the case of non-response trough plasma concentrations of 400 microg/L for (R,S)-methadone or 250 microg/L for (R)-methadone might be used as target values.