Therapeutic drug monitoring in inflammatory bowel diseases. Position statement of the Spanish Working Group on Crohn's Disease and Ulcerative Colitis

The treatment of inflammatory bowel disease has undergone a significant transformation following the introduction of biologic drugs. Thanks to these drugs, treatment goals have evolved from clinical response and remission to more ambitious objectives, such as endoscopic or radiologic remission. However, even though biologics are highly effective, a significant percentage of patients will not achieve an initial response or may lose it over time. We know that there is a direct relationship between the trough concentrations of the biologic and its therapeutic efficacy, with more demanding therapeutic goals requiring higher drug levels, and inadequate exposure being common. Therapeutic drug monitoring of biologic medications, along with pharmacokinetic models, provides us with the possibility of offering a personalized approach to treatment for patients with IBD. Over the past few years, relevant information has accumulated regarding its utility during or after induction, as well as in the maintenance of biologic treatment, in reactive or proactive strategies, and prior to withdrawal or treatment de-escalation. The aim of this document is to establish recommendations regarding the utility of therapeutic drug monitoring of biologics in patients with inflammatory bowel disease, in different clinical practice scenarios, and to identify areas where its utility is evident, promising, or controversial.

[Efficacy and safety of prophylaxis with emicizumab in hemophilia A: A study of 13 patients]

INTRODUCTION

Emicizumab is the first non-replacement therapy for prophylaxis in severe hemophilia A.

AIMS

The principal aim of this study is to describe the results of our patients in prophylaxis with emicizumab, according to the usual clinical practice.

MATERIAL AND METHODS

Follow-up of 13 patients from the start of prophylaxis, recording of bleeding, surgeries, adverse reactions and the need or not for factor therapy. Plasma levels were measured at follow-up visits, the technique was coagulative in one stage, modified by 1:20 dilution.

RESULTS

Median plasma levels were 52.2mg [30.7-71.9]. Prophylaxis was safe and effective; only one spontaneous haemorrhage was recorded over time and no treatment was required. There were no thromboembolic events or serious hypersensitivity, anaphylaxis or anaphylactoid reactions. The incidence of injection site reactions was 8%. Perioperative management in minor interventions was carried out without adjuvant factorial therapy, in 2 major surgeries a dose of plasmatic FVIII concentrate was required in the patient with hemophilia A without inhibitor and FVII in the patient with inhibitor, and it was sufficient to stop the bleeding.

CONCLUSION

This study demonstrated emicizumab pharmacokinetics and its half life ensure optimal levels with prophylaxis treatment at doses established in the technical data sheet.

[Translated article] Pharmacokinetics of eculizumab in adult and pediatric patients with atypical hemolytic uremic syndrome and C3 glomerulopathy

OBJECTIVE

The objective of the study was to analyze and describe the concentrations of eculizumab and the complement blockade in patients with atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy, and to define a therapeutic margin where there is a high probability of achieving therapeutic efficacy.

METHODS

Observational, ambispective, and multicenter study that included adult and pediatric patients diagnosed with aHUS and C3 glomerulopathy from September 2020 to October 2022 in 5 hospitals in Spain. Eculizumab was administered at the doses recommended by the data sheet according to the European Medicines Agency (EMA). Pre- and post-dose concentrations of eculizumab were determined, as well as blockade of the classical complement pathway (CH50). Sociodemographic and clinical data were collected, and pharmacokinetic parameters were calculated. To establish the cut-off point for eculizumab concentrations that predicted complement blockade, Receiver Operating Characteristic (ROC) curve analysis was performed. Lastly, the Kruskal-Wallis test was used to contrast the differences in different parameters according to eculizumab concentrations.

RESULTS

Twenty-five patients were included, 19 adults (76.0%) and 6 pediatrics (24.0%), with median ages of 43.4 (interquartile range (IQR) 35.7-48.8) and 10.1 (IQR 9.6-11.3) years, respectively. Of these, 22 (88.0%) patients were diagnosed with aHUS and 3 (12.0%) with C3 glomerulopathy. A total of 111 eculizumab concentrations were determined. Mean pre- and post-dose concentration values detected during the maintenance phase were 243.8 (SD 240.6) μg/mL and 747.4 (standard deviation (SD) 444.3) μg/mL, respectively. Increased complement blockade was observed at higher pre-dose concentrations (P = .002) and decreased serum creatinine at both higher pre- and post-dose concentrations (P = .001 and P = .017, respectively). Using ROC curves, it was determined that a pre-dose concentration >149.0 μg/mL was optimal to achieve complement blockade, with an AUC of 0.87 (0.78-0.95). Finally, high inter-individual (48.9% variation coefficient (CV)) with low intra-individual variabilities (11.9% CV) in eculizumab clearance were observed.

CONCLUSIONS

The present study reports supratherapeutic concentrations of eculizumab in patients with aHUS, and defines higher concentrations than those described in the data sheet to achieve blockade, thus encouraging the personalization of treatment with eculizumab.

Pharmacokinetics of eculizumab in adult and pediatric patients with atypical hemolytic uremic syndrome and C3 glomerulopathy

OBJECTIVE

The objective of the study was to analyze and describe the concentrations of eculizumab and the complement blockade in patients with atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy, and to define a therapeutic margin where there is a high probability of achieving therapeutic efficacy.

METHODS

Observational, ambispective and multicenter study that included adult and pediatric patients diagnosed with aHUS and C3 glomerulopathy from September 2020 to October 2022 in five hospitals in Spain. Eculizumab was administered at the doses recommended by the data sheet according to the European Medicines Agency (EMA). Pre-dose and post-dose concentrations of eculizumab were determined, as well as blockade of the classical complement pathway (CH50). Sociodemographic and clinical data were collected, and pharmacokinetic parameters were calculated. To establish the cut-off point for eculizumab concentrations that predicted complement blockade, Receiver Operating Characteristic (ROC) curve analysis was performed. Lastly, the Kruskal-Wallis test was used to contrast the differences in different parameters according to eculizumab concentrations.

RESULTS

Twenty-five patients were included, 19 adults (76.0%) and 6 pediatrics (24.0%), with median ages of 43.4 (IQR 35.7-48.8) and 10.1 (IQR 9.6-11.3) years, respectively. Of these, 22 (88.0%) patients were diagnosed with aHUS and 3 (12.0%) with C3 glomerulopathy. A total of 111 eculizumab concentrations were determined. Mean pre-dose and post-dose concentration values detected during the maintenance phase were 243.8 (SD 240.6) μg/mL and 747.4 (SD 444.3) μg/mL, respectively. Increased complement blockade was observed at higher pre-dose concentrations (p=0.002) and decreased serum creatinine at both higher pre- and post-dose concentrations (p=0.001 and p=0.017, respectively). Using ROC curves, it was determined that a pre-dose concentration >149.0 μg/mL was optimal to achieve complement blockade, with an AUC of 0.87 (0.78-0.95). Finally, high inter-individual (48.9% CV) with low intra-individual variabilities (11.9% CV) in eculizumab clearance were observed.

CONCLUSIONS

The present study reports supratherapeutic concentrations of eculizumab in patients with aHUS, and defines higher concentrations than those described in the data sheet to achieve blockade, thus encouraging the personalization of treatment with eculizumab.

Comparative effectiveness and drug survival of biosimilar infliximab CPT-13 vs. reference infliximab in inflammatory bowel disease: A retrospective cohort study

BACKGROUND

Studies have investigated the efficacy and safety of switching to the biosimilar infliximab (CT-P13) in patients with inflammatory bowel disease (IBD). However, there is limited research directly comparing the effectiveness, drug survival, and pharmacokinetic profiles of the reference infliximab (IFX) and CT-P13 in real clinical settings.

OBJECTIVE

To compare the effectiveness and drug survival of CPT-13 and reference IFX at weeks 26 and 52, and to determine the pharmacokinetic profiles and safety profile in real-world settings.

METHODS

A retrospective observational cohort analysis was conducted at a single center. The study compared the proportion of patients achieving clinical remission and experiencing poor clinical outcomes at weeks 26 and 52. The drug survival rate of CT-P13 and reference infliximab was also assessed during the follow-up period.

RESULTS

A total of 153 patients were included in the study, 39.2% receiving CPT-13 and 60.8% reference IFX. At week 26, clinical remission rates were 66.7% (CPT-13: 74.4% vs. reference IFX: 62.3%, p=0.178), and at week 52, they were 64% (CPT-13: 85.4% vs. reference IFX: 63.0%, p=0.012). Subgroup analysis with therapeutic drug monitoring (TDM) found no significant differences at week 26 (CPT-13: 74.4% vs. reference IFX: 58.8%, p=0.235) or at week 52 (CPT-13: 85.4% vs. reference IFX: 68.8%, p=0.153).

CONCLUSION

Our study demonstrates comparable efficacy, drug survival, pharmacokinetic profiles, and incidence of immunogenicity between both drugs in a real clinical setting. Further studies with greater statistical power are needed to validate these findings.

Definition of a therapeutic range for predicting long-term infliximab response in patients with inflammatory bowel disease

INTRODUCTION

Monitoring plasma levels of Infliximab plays an important role in optimising treatment in patients with inflammatory bowel disease (IBD). The aim of the following study has been to determine the predictive potential of monitoring infliximab plasma levels for sustained clinical response and evaluate its usefulness to improve treatment efficacy and symptom control, in patients with IBD.

METHODS

This single-centre retrospective study (2017-2019) included patients diagnosed with IBD treated with infliximab. Serum levels and the occurrence of drug-associated immunogenicity were analysed at Week 8 post-induction and 6, 12 and 24 months. Clinical parameters and inflammatory markers were recorded such as subjective global assessment (SGA), C-reactive protein (CRP) and faecal calprotectin (FC). Factors associated with early discontinuation and dose intensification of infliximab were determined.

RESULTS

Multivariate analysis determined that IFX concentrations>7μg/mL at week 8, and at 6 months, are associated with inflammatory remission (p=0.046, 0.045). IFX>7μg/mL at 12 months predicted remission at 18 months of treatment (p=0.006). IFX values>3μg/mL at 12 months are associated with stable SGA at 18 months (p=0.001). Such values at 18 months are associated with stable SGA at 24 months (p=0.044).

CONCLUSIONS AND RELEVANCE

The predictive potential of monitoring IFX plasma levels as a strategy to evaluate sustained long-term clinical response was confirmed. Our results highlight the importance of its introduction into routine clinical practice to enable early identification of non-responders, treatment optimisation, relapse prevention and improve long-term therapy maintenance.

Trypanocidal treatment of Chagas disease

Chagas disease is a neglected parasitosis caused by the protozoan parasite Trypanosoma cruzi. This infection is present in most Latin American countries, although, due to migratory movements, it is a growing cause for concern in non-endemic countries. The only two drugs currently available for its treatment-benznidazole and nifurtimox-were marketed 50 years ago. While they are very effective for acute and recent infection, and for the prevention of maternofoetal transmission, their efficacy declines in people who have chronic infection, especially those older than 18 years of age. In the presence of visceral involvement, parasiticidal treatment is of little or no value. The safety profile of both drugs is far from ideal, with frequent adverse events and high rates of drug discontinuation, mainly in adults. So far, new drugs and new strategies have not been shown to improve the results of the current nitroimidazoles, although the results are promising. In this review, we focus on the aspects that allow clinicians to make the best use of currently available drugs. In addition, we discuss new therapeutic options and ongoing research in the field.

[Liposomal amphotericin B: Clinical pharmacology, pharmacokinetics and pharmacodynamics]

Liposomal amphotericin B is a lipid formulation of the antifungal drug amphotericin B with some distinguishing characteristics in its pharmacological behavior that entail some clinical differences of great interest. The significant improvement in the systemic and renal tolerability is one of them. This fact is related to the great stability of the liposome, promoted by its negative charge, the presence of cholesterol and the remarkable thermo-stability of the remaining lipids that compose it. In this situation, amphotericin B seems to be released from the liposome not spontaneously but when the liposome binds to the ergosterol in the fungal cell membrane. For this reason, there is almost no free amphotericin B in plasma or tissues, although it seems that its availability is greater when there is fungal infection. As a consequence, when the pharmacokinetic behavior is studied, the concentration and availability of liposomal amphotericin B are very high, and its volume of distribution is reduced in comparison with the other formulations.

Trypanocidal treatment of Chagas disease

Chagas disease is a neglected parasitosis caused by the protozoan parasite Trypanosoma cruzi. This infection is present in most Latin American countries, although, due to migratory movements, it is a growing cause for concern in non-endemic countries. The only two drugs currently available for its treatment-benznidazole and nifurtimox-were marketed 50 years ago. While they are very effective for acute and recent infection, and for the prevention of maternofoetal transmission, their efficacy declines in people who have chronic infection, especially those older than 18 years of age. In the presence of visceral involvement, parasiticidal treatment is of little or no value. The safety profile of both drugs is far from ideal, with frequent adverse events and high rates of drug discontinuation, mainly in adults. So far, new drugs and new strategies have not been shown to improve the results of the current nitroimidazoles, although the results are promising. In this review, we focus on the aspects that allow clinicians to make the best use of currently available drugs. In addition, we discuss new therapeutic options and ongoing research in the field.

Regulation of hypnosis in Propofol anesthesia administration based on non-linear control strategy

Continuous adjustment of Propofol in manual delivery of anesthesia for conducting a surgical procedure overburdens the workload of an anesthetist who is working in a multi-tasking scenario. Going beyond manual administration and Target Controlled Infusion, closed-loop control of Propofol infusion has the potential to offer several benefits in terms of handling perturbations and reducing the effect of inter-patient variability. This paper proposes a closed-loop automated drug administration approach to control Depth Of Hypnosis in anesthesia. In contrast with most of the existing research on anesthesia control which makes use of linear control strategies or their improved variants, the novelty of the present research lies in applying robust control strategy i.e. Sliding Mode Control to accurately control drug infusion. Based on the derived patient's model, the designed controller uses measurements from EEG to regulate DOH on Bispectral Index by controlling infusion rate of Propofol. The performance of the controller is investigated and characterized with real dataset of 8 patients undergoing surgery. Results of this in silico study indicate that for all the patients, with 0% overshoot observed, the steady state error lies in between ±5. Clinically, this implies that in all the cases, without any overdose, the controller maintains the desired DOH level for smooth conduction of surgical procedures.

[Mechanisms of action, pharmacology and interactions of dolutegravir]

Dolutegravir is a second-generation integrase strand transfer inhibitor (INSTI), whose potential and binding half-life in the integrase are far superior to those of raltegravir and elvitegravir, conferring it with unique characteristics in terms of its genetic barrier to resistance and activity against viruses with one or more mutations in the integrase. The pharmacokinetic properties of dolutegravir allow once-daily dosing (50 mg), with or without food, maintaining concentrations far above those effective against wild-type viruses. If integrase resistance mutations are present, the recommended dosing regimen is 50 mg/12 h. The distribution of dolutegravir in cerebrospinal fluid is good and effective concentrations are also reached in the male and female genital tracts. Dolutegravir is metabolized by UGT1A1 and, to a lesser extent, by CYP3A4, without being an inducer or inhibitor of the usual metabolic systems. It has a very low potential for drug interactions and can be administered in routine doses with most drugs. Dose adjustment is not required, even in patients with renal insufficiency or mild or moderate liver failure. Increasing the dose of dolutegravir (50 mg/12 h) is only recommended when administered with efavirenz, nevirapine, fosamprenavir/r, tipranavir/r, rifampicin, carbamazepine, phenytoin and phenobarbital. Coadministration of dolutegravir with etravirine is not recommended without a protease inhibitor or with Hypericum perforatum. Dolutegravir should be administered 2 h before or 6 h after antacids or products with polyvalent cations. Dolutegravir can reduce renal tubule secretion of substances excreted via OCT2, with a slight initial increase in creatinine, with no risk of renal toxicity. The drug can also increase metformin concentrations and consequently monitoring is recommended in case dose adjustment is required. In summary, dolutegravir has excellent pharmacokinetic and drug interaction profiles.

[Regulation of hypnosis in Propofol anesthesia administration based on non-linear control strategy]

Continuous adjustment of Propofol in manual delivery of anesthesia for conducting a surgical procedure overburdens the workload of an anesthetist who is working in a multi-tasking scenario. Going beyond manual administration and Target Controlled Infusion, closed-loop control of Propofol infusion has the potential to offer several benefits in terms of handling perturbations and reducing the effect of inter-patient variability. This paper proposes a closed-loop automated drug administration approach to control Depth Of Hypnosis in anesthesia. In contrast with most of the existing research on anesthesia control which makes use of linear control strategies or their improved variants, the novelty of the present research lies in applying robust control strategy i.e. Sliding Mode Control to accurately control drug infusion. Based on the derived patient's model, the designed controller uses measurements from EEG to regulate DOH on Bispectral Index by controlling infusion rate of Propofol. The performance of the controller is investigated and characterized with real dataset of 8 patients undergoing surgery. Results of this in silico study indicate that for all the patients, with 0% overshoot observed, the steady state error lies in between ±5. Clinically, this implies that in all the cases, without any overdose, the controller maintains the desired DOH level for smooth conduction of surgical procedures.

Comparison of the Cortínez and the Schnider models with a targeted effect-site TCI of 3 mcg/ml in biophase in healthy volunteers

OBJECTIVE

To compare the Cortínez and Schnider models in effect-site TCI mode (3 mcg/ml) in healthy volunteers.

METHODS

Ten healthy volunteers were prospectively studied on 2 occasions. Propofol was administered with the Cortínez or the Schnider models, as randomly assigned. Times and predicted concentrations at the time of loss and recovery of consciousness (LOC and ROC), mass of drug administered, BIS, and haemodynamic variables were compared. Statistical analysis was with paired Wilcoxon test. A P<.05 was considered significant.

RESULTS

The propofol bolo was higher (1.4 [1.3-1.6] versus 0.9 [0.7-1.3] mg/kg, P=.005) and the LOC occurred earlier (1.33 [0.67-6.83] versus 3.87 [1.66-11.08] minutes, P=.02) with the Cortínez model compared to the Schnider model. With the Cortínez model, LOC occurred at an effect site concentrations of 2.6 (1.65-3.0) mcg/ml. With the Schnider model, LOC occurred at 3.87 min (1.66-11.8) after reaching the target of 3 mcg/ml. (P=.001). BIS values, infusion rates, and haemodynamic variables were similar between models after 20minutes of infusion (P>.5). Recovery (ROC) was longer with the Cortínez model (11.6 [8.1-16.2] vs. 8.5 [4.7-15.5] min, P=.003).

CONCLUSIONS

The Cortínez model is a good alternative to the Schnider model for use in effect-site TCI mode in normal weight subjects. With the target used in this study (3 mcg/ml), the slower Ke0 incorporated into the Cortínez model better discriminated the LOC time.

[Aflibercept. An approach to pharmacology]

Aflibercept is a fusion protein whose chemical structure combines the constant fraction of any IgG with a variable fraction constructed with fundamental parts of VEGF receptors. Consequently, it is able to bind to various VEGF as well as to placental growth factor (PIGF), which has been related to a possible synergistic effect in efficacy. The affinity of this drug is higher than that of ranibizumab and bevacizumab. Moreover, it has an intraocular antiinflammatory effect. Intravitreal administration leads to the presence of traces of the drug in plasma but the concentrations are so reduced that the presence of systemic adverse effects, including arterial hypertension, is practically nil. Because of its prolonged intraocular elimination half-life and high affinity, the drug can be administered in convenient regimens, since, after an initial monthly injection for the first three doses, the interval between injections is increased to one every two months and, after the first 12 months, the dosing will depend on the visual and anatomical results.

Comparison of the hemodynamic response to induction and intubation during a target-controlled infusion of propofol with 2 different pharmacokinetic models. A prospective ramdomized trial

OBJECTIVE

Determine the best propofol pharmacokinetic model that meets patient requirements and is devoid of major haemodynamic side effects.

MATERIAL AND METHODS

Prospective, randomised, open-label, clinical trial was performed on an intention to treat basis. It included 280 patients with ASA physical status i-iii, aged 18 to 80 years and weight range between 45 to 100kg, scheduled for surgery under general anaesthesia. They were randomized into 2 groups according to the pharmacokinetic model: Modified Marsh group and Schnider group. The haemodynamic changes that occurred during the induction and intubation were analysed. A propofol target controlled infusion was started to achieve and maintain a bispectral index value between 35 and 55. At minute 6, orotracheal intubation was performed and the study finished at minute 11. Heart rate, mean arterial pressure and their product (HR×MAP) were measured and recorded every minute throughout the study. Every HR×MAP value was compared to its baseline value to determine the minimum value before intubation, the maximum value after intubation, the maximum variation after intubation, and its final value. The GRADIENTE (MIN, MAX) variable (primary endpoint of this study) analyses the difference between maximal and minimal values related to intubation. Propofol doses and calculated concentrations and any hypotensive events were also recorded.

RESULTS

No differences were found between groups regarding haemodynamic performance. GRADIENTE (MIN, MAX) values and the percentage of hypotensive events were: Modified Marsh group median 77.41% vs. Schnider group 84.86% (p= 0.821) and 17.3% vs. 12.8% (p = 0.292), respectively.

CONCLUSION

The study failed to demonstrate any haemodynamic difference between the 2 groups, even though the Modified Marsh group received a larger dose of propofol.

[Pharmacokinetics and pharmacodynamics of ceftaroline]

Ceftaroline is administered intravenously in the form of a prodrug, ceftaroline fosamil, which is rapidly hydrolyzed by plasma phosphatases to its active form, ceftaroline. In general, the pharmacokinetics of ceftaroline differ little from those of other cephalosporins. A proportional increase in both the peak plasma concentration (Cmax) and the area under the curve (AUC) have been observed when the drug is administered in increasing doses, which demonstrates its linear pharmacokinetics. Half the dose of ceftaroline is excreted actively through the kidneys. The pharmacokinetic parameters of ceftaroline administered through the intramuscular route in diverse animal species were similar to those observed when the drug was administered intravenously and consequently clinical research into ceftaroline administered through this alternative route would be appropriate. Patients with moderate-severe alterations of renal function and those undergoing hemodialysis require dose adjustments. There is limited experience of the pharmacokinetics of ceftaroline in children, which has given rise to several schedules stratified by age groups. The pharmacodynamics of the drug have been studied in models of animal infection and in in vitro infections caused mainly by Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA], strains with intermediate vancomycin sensitivity [hVISA or hGISA]) and by Streptococcus pneumoniae strains with distinct sensitivities to penicillin. Because ceftaroline is a time-dependent antibiotic, the most widely studied pharmacokinetic/pharmacodynamic (PK/PD) indicator is the time interval during which drug concentrations are maintained above the minimum inhibitory concentration (MIC), calculated both as total drug (T > MIC) and as free fraction of the drug (fT > MIC). The PK/PD simulations carried out in these models, developed on the basis of the concentrations obtained with routine doses in humans, have shown that ceftaroline has a good PK/PD profile against these microorganisms, including strains with reduced sensitivity to vancomycin, linezolid, and daptomycin.

Evaluation of the reproducibility of a protocol for the pharmacokinetic study of breast tumors by dynamic magnetic resonance imaging

OBJECTIVE

To evaluate the reproducibility of a protocol for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for the pharmacokinetic study of breast tumors.

MATERIAL AND METHODS

We carried out this prospective study from October 2009 through December 2009. We studied 12 patients with stage ii-iii invasive breast cancer without prior treatment. Our center's research ethics committee approved the study. The 12 patients underwent on two consecutive days DCE-MRI with a high temporal resolution protocol (21 acquisitions/minute). The data obtained in an ROI traced around the largest diameter of the tumor (ROI 1) and in another ROI traced around the area of the lesion's highest K(trans) intensity (ROI 2) were analyzed separately. We used parametric and nonparametric statistical tests to study the reproducibility and concordance of the principal pharmacokinetic variables (K(trans), Kep, Ve and AUC90).

RESULTS

The correlations were very high (r>.80; P<.01) for all the variables for ROI 1 and high (r=.70-.80; P<.01) for all the variables for ROI 2, with the exception of Ve both in ROI 1 (r=.44; P=.07) and in ROI 2 (r=.13; P=.235). There were no statistically significant differences between the two studies in the values obtained for K(trans), Kep and AUC90 (P>.05 for each), but there was a statistically significant difference between the two studies in the values obtained for Ve in ROI 2 (P=.008).

CONCLUSIONS

The high temporal resolution protocol for DCE-MRI used at out center is very reproducible for the principal pharmacokinetic constants of breast.

Effects of inhalational anaesthesia with low tidal volume ventilation on end-tidal sevoflurane and carbon dioxide concentrations: prospective randomized study

OBJECTIVE

We investigated how ventilation with low tidal volumes affects the pharmacokinetics of sevoflurane uptake during the first minutes of inhaled anaesthesia.

METHODS

Forty-eight patients scheduled for lung resection were randomly assigned to three groups. Patients in group 1, 2 and 3 received 3% sevoflurane for 3 min via face mask and controlled ventilation with a tidal volume of 2.2, 8 and 12 ml kg(-1), respectively (Phase 1). After tracheal intubation (Phase 2), 3% sevoflurane was supplied for 2 min using a tidal volume of 8 ml kg(-1) (Phase 3).

RESULTS

End-tidal sevoflurane concentrations were significantly higher in group 1 at the end of phase 1 and lower at the end of phase 2 than in the other groups as follows: median of 2.5%, 2.2% and 2.3% in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 1.7%, 2.1% and 2.0% in phase 2, respectively (P<0.001). End-tidal carbon dioxide values in group 1 were significantly lower at the end of phase 1 and higher at the end of phase 2 than in the other groups as follows: median of 16.5, 31 and 29.5 mm Hg in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 46.2, 36 and 33.5 mm Hg in phase 2, respectively (P<0.001).

CONCLUSION

When sevoflurane is administered with tidal volume approximating the airway dead space volume, end-tidal sevoflurane and end-tidal carbon dioxide may not correctly reflect the concentration of these gases in the alveoli, leading to misinterpretation of expired gas data.

Methotrexate: new therapeutic approaches

Although the first study on the efficacy of methotrexate in the treatment of psoriasis was reported in 1958, scientific evidence for this indication has been scant until quite recently. We now have new data on the pharmacokinetics and mechanism of action of methotrexate and new subcutaneous formulations that have improved the bioavailability, efficacy, and ease of administration of the drug. The results of recent clinical trials comparing methotrexate with several biologic agents have shown it to be the first-line therapy among the classic systemic treatments for psoriasis. Moreover, the incremental cost-effectiveness ratio for subcutaneous methotrexate has been shown to be superior to that of ciclosporin, adalimumab, and infliximab.