Genetic Variants Associated with Biological Treatment Response in Inflammatory Bowel Disease: A Systematic Review

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the digestive tract usually characterized by diarrhea, rectal bleeding, and abdominal pain. IBD includes Crohn's disease and ulcerative colitis as the main entities. IBD is a debilitating condition that can lead to life-threatening complications, involving possible malignancy and surgery. The available therapies aim to achieve long-term remission and prevent disease progression. Biologics are bioengineered therapeutic drugs that mainly target proteins. Although they have revolutionized the treatment of IBD, their potential therapeutic benefits are limited due to large interindividual variability in clinical response in terms of efficacy and toxicity, resulting in high rates of long-term therapeutic failure. It is therefore important to find biomarkers that provide tailor-made treatment strategies that allow for patient stratification to maximize treatment benefits and minimize adverse events. Pharmacogenetics has the potential to optimize biologics selection in IBD by identifying genetic variants, specifically single nucleotide polymorphisms (SNPs), which are the underlying factors associated with an individual's drug response. This review analyzes the current knowledge of genetic variants associated with biological agent response (infliximab, adalimumab, ustekinumab, and vedolizumab) in IBD. An online literature search in various databases was conducted. After applying the inclusion and exclusion criteria, 28 reports from the 1685 results were employed for the review. The most significant SNPs potentially useful as predictive biomarkers of treatment response are linked to immunity, cytokine production, and immunorecognition.

How can artificial intelligence optimize value-based contracting?

Efforts in the pharmaceutical market have been aimed at ensuring that the benefits obtained from the introduction of new therapies justify the associated costs. In recent years, drug payment models in healthcare have undergone a dramatic shift from focusing on volume (i.e., size of the target clinical population) to focusing on value (i.e., drug performance in real-world settings). In this context, value-based contracts (VBCs) were designed to align the payment of a drug to its clinical performance outside clinical trials by evaluating the effectiveness using real-word evidence (RWE). Despite their widespread implementation, different factors jeopardize the application of VBCs to most marketed drugs in a near future, including the need for easily measurable and relevant outcomes associated with clinical improvements, and access to a large patient population to assess said outcomes. Here, we argue that the extraction and analysis of massive amounts of RWE captured in patients' electronic health records (EHRs) will circumvent these issues and optimize negotiations in VBCs. Particularly, the use of Natural Language Processing (NLP) has proven successful in the analysis of structured and unstructured clinical information in EHRs in multicenter research studies. Thus, the application of NLP to analyze patient-centered information in EHRs in the context of innovative contracting can be utterly beneficial as it enables the real-time evaluation of treatment response and financial impact in real-world settings.

Matching-Adjusted Indirect Comparison of Efficacy and Consumption of rVIII-SingleChain Versus Two Recombinant FVIII Products Used for Prophylactic Treatment of Adults/Adolescents with Severe Haemophilia A

Introduction

Given the relatively small number of patients with haemophilia A, head-to-head comparisons between recombinant FVIII (rFVIII) products are difficult to conduct. This study compared the efficacy and consumption of rVIII-SingleChain (lonoctocog alfa, AFSTYLA^®) with rAHF-PFM (octocog alfa, Advate^®) and rFVIIIFc (efmoroctocog alfa, Elocta^®), for the prophylaxis and treatment of bleeding episodes in previously treated adolescents/adults with severe haemophilia A, through a matching-adjusted indirect comparison (MAIC).

Methods

A systematic literature review identified published clinical trials for rAHF-PFM and rFVIIIFc. Individual patient data for rVIII-SingleChain were used to match baseline patient characteristics to those from published trials, using an approach similar to propensity score weighting. After matching, annualized bleeding rates (ABR), percentage of patients with zero bleeds, and rFVIII consumption were compared across trial populations.

Results

Published data were identified from two rAHF-PFM trials and one rFVIIIFc trial. rVIII-SingleChain had similar ABR (risk ratio [RR]: 0.74 [0.16; 3.48]; RR: 1.18 [0.85; 1.65]) and percentage of patients with zero bleeds (odds ratio [OR]: 1.34 [0.56; 3.22]; OR: 0.78 [0.47; 1.31]) versus rAHF-PFM and rFVIIIFc, respectively. Annual rVIII-SingleChain consumption was significantly lower than rAHF-PFM (mean difference: − 1507.66 IU/kg/year [− 2011.71; − 1003.61]) and equivalent to rFVIIIFc (RR: 0.96 [0.62; 1.49]).

Conclusion

Although limited to published information for comparator trials, these results suggest that with an annualized rFVIII consumption comparable to rFVIIIFc, but significantly lower than rAHF-PFM, routine prophylaxis with rVIII-SingleChain is able to maintain a similar ABR and percentage of patients with zero bleeds, attesting to the long-acting nature of rVIII-SingleChain.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-021-01853-0.

It is difficult to directly compare different recombinant FVIII products in head-to-head studies because there are few patients with haemophilia A. This study aimed to indirectly compare the efficacy and consumption of different recombinant FVIII products in the prophylactic treatment of haemophilia A using published clinical data. A proven method for performing indirect comparisons of products is referred to as a matching-adjusted indirect comparison. Using this approach, we were able to compare rVIII-SingleChain with two other recombinant FVIII products (rAHF-PFM and rFVIIIFc). Our results suggest that annual FVIII consumption with rVIII-SingleChain is comparable to rFVIIIFc, but is significantly lower than rAHF-PFM, while maintaining a similar bleeding rate. These results highlight the long-acting nature of the product.

Clinical benefits of a Bayesian model for plasma-derived factor VIII/VWF after one year of pharmacokinetic-guided prophylaxis in severe/moderate hemophilia A patients

INTRODUCTION

Individual pharmacokinetic (PK) profiling in hemophilia A (HA) helps to individualize prophylaxis using population PK models (popPK). A specific popPK model for plasma-derived factor VIII containing von-Willebrand Factor (pdFVIII/VWF) was developed.

AIM

To compare standard versus PK-driven prophylaxis, using a generic or a specific popPK model for pdFVIII/VWF.

MATERIALS AND METHODS

A prospective study conducted in HA patients in prophylaxis with pdFVIII/VWF (Fanhdi®) comparing three one-year study periods: (1) standard prophylaxis, (2) PK-guided prophylaxis using a generic pdFVIII popPK model which described FVIII activity irrespective of FVIII concentrate, and (3) PK-guided prophylaxis with specific pdFVIII/VWF popPK model. PK parameters analyzed were half-life, trough levels (TL) at 24, 48 and 72 h, and time to reach FVIII levels of 1, 2, 5% (T5%). Clinical outcomes were dose/kg, FVIII consumption, annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR), spontaneous and traumatic bleeds.

RESULTS

Of the 30 analyzed patients, 28 had severe HA and the median age was 31.2. Fifteen patient's prophylaxis doses were PK-adjusted. After the generic PK-guided prophylaxis period, younger patients showed more joint bleeds, a shorter half-life, and lower TL48, TL72 and T5%. Using the specific pdFVIII/VWF popPK model compared with standard prophylaxis, a lower spontaneous AJBR was observed in the entire cohort and in patients aged >15 years. Additionally, lower spontaneous ABR was reported in patients aged ≤15 years comparing specific and generic models.

CONCLUSIONS

PK-guided prophylaxis with a specific pdFVIII/VWF popPK model allowed treatment individualization and improved bleeding control in routine clinical practice, especially in younger patients with short pdFVIII/VWF half-lives.

Mortality, falls and fracture risk are positively associated with frailty: a SIDIAP cohort study of 890,000 patients

Background

Frail subjects are at increased risk of adverse outcomes. We aimed to assess their risk of falls, all-cause mortality, and fractures.

Method

We used a retrospective cohort study using the Sistema d’Informació per al Desenvolupament de l’Investigació en Atenció Primària database (>6 million residents). Subjects aged 75 years and older with ≥1 year of valid data (2007–2015) were included. Follow-up was carried out from (the latest of) the date of cohort entry up to migration, end of the study period or outcome (whichever came first). The eFRAGICAP classified subjects as fit, mild, moderate, or severely frail. Outcomes (10th revision of the International Classification of Diseases) were incident falls, fractures (overall/hip/vertebral), and all-cause mortality during the study period. Statistics: hazard ratios (HRs), 95% CI adjusted (per age, sex, and socioeconomic status), and unadjusted cause-specific Cox models, accounting for competing risk of death (fit group as the reference).

Results

A total of 893 211 subjects were analyzed; 54.4% were classified as fit, 34.0% as mild, 9.9% as moderate, and 1.6% as severely frail. Compared with the fit, frail had an increased risk of falls (adjusted HR [95% CI] of 1.55 [1.52–1.58], 2.74 [2.66–2.84], and 5.94 [5.52–6.40]), all-cause mortality (adjusted HR [95% CI] of 1.36 [1.35–1.37], 2.19 [2.16–2.23], and 4.29 [4.13–4.45]), and fractures (adjusted HR [95% CI] of 1.21 [1.20–1.23], 1.51 [1.47–1.55], and 2.36 [2.20–2.53]) for mild, moderate, and severe frailty, respectively. Severely frail had a high risk of vertebral (HR of 2.49 [1.99–3.11]) and hip fracture (HR [95% CI] of 1.85 [1.50–2.28]). Accounting for competing risk of death did not change results.

Conclusion

Frail subjects are at increased risk of death, fractures, and falls. The eFRAGICAP tool can easily assess frailty in electronic primary care databases in Spain.

Towards a symbiotic relationship between big data, artificial intelligence, and hospital pharmacy

The digitalization of health and medicine and the growing availability of electronic health records (EHRs) has encouraged healthcare professionals and clinical researchers to adopt cutting-edge methodologies in the realms of artificial intelligence (AI) and big data analytics to exploit existing large medical databases. In Hospital and Health System pharmacies, the application of natural language processing (NLP) and machine learning to access and analyze the unstructured, free-text information captured in millions of EHRs (e.g., medication safety, patients’ medication history, adverse drug reactions, interactions, medication errors, therapeutic outcomes, and pharmacokinetic consultations) may become an essential tool to improve patient care and perform real-time evaluations of the efficacy, safety, and comparative effectiveness of available drugs. This approach has an enormous potential to support share-risk agreements and guide decision-making in pharmacy and therapeutics (P&T) Committees.

Childhood overweight and obesity and back pain risk: a cohort study of 466 997 children

OBJECTIVES

To assess the association between age, sex, socioeconomic group, weight status and back pain risk in a large general population cohort of children.

DESIGN AND SETTING

A dynamic cohort of children aged 4 years in the Information System for Research in Primary Care (SIDIAP) electronic primary care records data in Catalonia. Multivariable Cox models were fitted to explore the association between back pain and weight status categories according to the WHO 2007 growth reference groups (body mass index for age z-score). Models were adjusted for age, sex, socioeconomic status and nationality.

PARTICIPANTS

Children seen at age 4 years at paediatric primary care clinics between 1 January 2006 and 31 December 2013 and followed up until 31 December 2016 or age 15 years.

OUTCOME MEASURES

Incident back pain registered by paediatricians at primary care using the International Statistical Classification of Diseases and Health Related Problems, 10th Edition code M54.

RESULTS

466 997 children were followed for a median 5.0 years (IQR 5.1). In multivariable models, overweight and obesity increased back pain risk, with adjusted HRs of 1.18 (95% CI 1.09 to 1.27) and 1.34 (95%CI 1.19 to 1.51) for overweight and obesity, respectively. Females were at greater risk of back pain than males with adjusted HR 1.40 (95%CI 1.35 to 1.46). Adjusted HR was 1.43 (95%CI 1.33 to 1.55) for back pain in children from the most deprived socioeconomic groups compared with the least deprived socioeconomic groups.

CONCLUSIONS

Maintaining a healthy weight from an early age may reduce the prevalence of back pain in both children and adults. Overweight female children from deprived socioeconomic groups are at greatest risk of back pain and represent a target population for intervention.

Intravitreal melphalan therapy for vitreous seeds in retinoblastoma: Implementation and outcomes of a new chemotherapy protocol

Retinoblastoma is the most common paediatric ocular tumour, which appears in the retina. Without treatment, retinoblastoma grows and destroys the internal ocular globe architecture, even leading to metastasis. When treated, overall survival is close to 97%, the alkylating drug melphalan being the most extensively used chemotherapeutic agent in localised treatment. The aim of this study is to describe the implementation of a new intravitreal chemotherapy retinoblastoma treatment protocol for children implanting vitreous seeds through intravitreal melphalan injections and to evaluate the patients' health outcomes treated with it. Between December 2014 and July 2018, seven patients were treated with this protocol. They received a mean of 3.3 cycles of intravitreal melphalan with standard doses of 30 mcg per cycle. In the seven eyes treated in our hospital, the response was as expected; three eyes with vitreous seedings (43%) were successfully treated. The main adverse effects presented by all patients were scars at cryogenisation points. In two patients, the appearance of 'salt and pepper' retinopathy was reported. Oncology pharmacists, as part of the treatment team, can provide information about recommended doses, expected adverse effects, stability of preparations, most appropriate method of processing, packaging, and methods of drug administration, to ensure efficacy and especially safety in the administration of these drugs.

Cost-effectiveness of Cladribine Tablets and fingolimod in the treatment of relapsing multiple sclerosis with high disease activity in Spain

OBJECTIVE

To estimate the cost-effectiveness of Cladribine Tablets in the treatment of relapsing multiple sclerosis (RMS) with high disease activity compared with fingolimod, from the perspective of the National Health System (NHS) in Spain.

METHODS

A Markov model was developed. The annual transition probabilities, were adjusted to patients with RMS with high disease activity. The effect of the treatments compared on the Expanded Disability Status Scale (EDSS) was modeled by hazard ratios for the confirmed progression of disability. The annual relapse rate and the probability of suffering adverse reactions were obtained from a meta-analysis and the literature. The derived costs were calculated from Spanish unit costs. The utilities were obtained from the CLARITY clinical trial and the literature. Deterministic and probabilistic sensitivity analyzes were performed.

RESULTS

Cladribine tablets was the dominant treatment: lower costs (-86,536 €) and more effective (+1.11 quality-adjusted life years - QALYs) compared to fingolimod. The probability that Cladribine Tablets was cost-effective compared to fingolimod ranged between 94.6% and 96.1% for willingness to pay from € 20,000 to € 30,000 per QALY gained.

CONCLUSIONS

Cladribine Tablets is a cost-effective treatment, compared to fingolimod, for the treatment of RMS with high disease activity.

EXPERT OPINION

According to the present study, compared to fingolimod, treatment with Cladribine Tablets of relapsing multiple sclerosis with high disease activity is an option that could generate savings for the Spanish National Health System, with a considerable gain in QALYs. Cladribine Tablets is considered cost-effective and dominant (less costs and more effectiveness) than fingolimod treatment option in this population.

Impact of NADPH oxidase functional polymorphisms in acute myeloid leukemia induction chemotherapy

Efficacy and toxicity of anthracycline treatment in acute myeloid leukemia (AML) is mediated by reactive oxygen species (ROS). NADPH oxidase is the major endogenous source of ROS and a key mediator of oxidative cardiac damage. The impact of NADPH oxidase polymorphisms (CYBA:rs4673, NCF4:rs1883112, RAC2:rs13058338) was evaluated in 225 adult de novo AML patients. Variant alleles of NCF4 and RAC2 were related to higher complete remission (P=0.035, P=0.016), and CYBA homozygous variant showed lower overall survival with recessive model (P=0.045). Anthracycline-induced cardiotoxicity was associated to NCF4 homozygous variant (P=0.012) and CYBA heterozygous genotype (P=0.027). Novel associations were found between variant allele of CYBA and lower lung and gastrointestinal toxicities, and a protective effect in nephrotoxicity and RAC2 homozygous variant. Moreover, RAC2 homozygous variant was related to delayed thrombocytopenia recovery. This study supports the interest of NADPH oxidase polymorphisms regarding efficacy and toxicity of AML induction therapy, in a coherent integrated manner.

The view of experts on initiatives to be undertaken to promote equity in the access to orphan drugs and specialised care for rare diseases in Spain: A Delphi consensus

OBJECTIVES

To reach a consensus amongst experts on the most feasible actions to be undertaken to facilitate patient access to specialised care and orphan drugs (OD) in the public health sector in Spain.

METHODS

Two Delphi rounds were completed. The questionnaire was based on a literature review and 2 focus groups. Agreement was sought on the desire (D) and prognosis (P) for the implementation within the next 5 years, on a 5-point Likert scale. Consensus was reached when ≥75% participants chose agreement (1-2) or disagreement options (4-5).

RESULTS

82 experts on rare disease (RD) participated. Agreement on the D and P was reached in 66.07% statements: OD pricing review [absence of clinical effectiveness (D:85.37%; P:85.90%), target population increase (D:79.27%; P:91.03%)]; reference team definition of referral protocols and clinical practice guidelines (D: 97.56%; P: 89.74%); and a unified, usable, etiology-based registry (D:97.56%; P:84.62%). D and P assessment diverged in 32.14% items: creation of a specific funding system for OD (D: 97.56%; P: 60.25%); and a network of medical teams to coordinate the care of RD patients (D: 99%; P: 62%).

CONCLUSIONS

The results have shown the need to promote dialogue between stakeholders, introduce European recommendation to national and regional Spanish policies and set up priorities and undertake actions to drive relevant changes in current medical practice in managing RD patients.

Pre and post intervention study of antiblastic drugs contamination surface levels at a Pharmacy Department Compounding Area using a closed system drug transfer device and a decontamination process

Assuring healthcare workers security on Hazardous Drugs (HD) compounding is critical in healthcare settings. Our study aims to demonstrate that the use of a Close System drug Transfer Device (CSTD) PhaSeal™ added to a decontamination process reduces antiblastic surface contamination levels in the Compounding Area (CA) of our Pharmacy Department (PD). We selected cyclophosphamide, 5-fluorouracil and iphosphamide to be evaluated. Testing was carried out with a wipe kit and quantified by an independent laboratory. We defined four sampling times: baseline; just after a decontamination procedure, which was repeated weekly during the study; four months after introduction of CSTD PhaSeal™ for cyclophosphamide and 5-fluorouracil compounding; and after eight months using CSTD PhaSeal™ for cyclophosphamide and 5-fluorouracil and one month for iphosphamide compounding. There was a decrease at the number of positive samples at the beginning/end of the study for all the drugs tested: 28/15 for cyclophosphide, 29/23 for iphosphamide and 7/1 for 5-fluorouracile. Comparing to the baseline, median cyclophosphamide levels significantly decreased (p-value <0.001) at 4 and 8 months sampling time (baseline: 1.01 ng/cm² to 0.06 ng/cm² and 0.01 ng/cm²), and median iphosphamide levels significantly decreased (p < 0.001) at 8 months sampling time (baseline: 3.02 ng/cm² to 0.06 ng/cm²). 5-Fluorouracil did not show significant differences between the sampling times (baseline: 0.09 ng/cm² to 0.09 ng/cm²). We saw a significant increase at iphosphamide levels at 4 months sampling point, contrary to cyclophosphamide, which levels had decreased. The use of CSTD PhaSeal™ for iphosphamide compounding the last month was implemented for ethical reasons after this intermediate results review. Our study suggests that the use of CSTD PhaSeal™, adding to decontaminating procedures, significantly reduces antiblastic drug surface levels at the CA of our PD.

Implication of Haemodiafiltration Flow Rate on Amikacin Pharmacokinetic Parameters in Critically Ill Patients

BACKGROUND

To analyse the effect of haemodiafiltration (CVVHDF) flow rate on amikacin pharmacokinetics and blood concentrations.

METHODS

Prospective observational study. Patients receiving CVVHDF and amikacin treatment were included. Pharmacokinetic parameters were calculated using Bayesian analysis. Spearman correlation test was used in order to assess the influence of CVVHDF flux on amikacin minimum concentration (Cmin) and plasma clearance.

RESULTS

Thirty patients undergoing CVVHDF procedures were included. The treatment with amikacin started at an initial mean dose of 12.4 (4.1) mg/kg/day. An association between the flow rate and Cmin value (r = 0.261; p = 0.161) and plasma clearance was found (r = 0.268; p = 0.152). Four patients (13.3%) were not able to achieve peak concentration over MIC value higher than 8. In 4 patients, amikacin had to be discontinued due to a high Cmin value.

CONCLUSIONS

Amikacin clearance in patients with CVVHDF is affected by the flow rate used. Therefore, CVVHDF dose should be taken into account when dosing amikacin.

Haemodialysis significantly reduces serum levetiracetam levels inducing epileptic seizures: Case report

WHAT IS KNOWN AND OBJECTIVE

Levetiracetam is used in the treatment of some forms of epilepsy. In renal impairment and patients on chronic haemodialysis, dose adjustment is required. We report a case.

CASE DESCRIPTION

This case report describes a woman on levetiracetam treatment who presented with generalized tonic-clonic seizures during a haemodialysis session. We report on treatment adjustment and on the impact of dialysis on levetiracetam levels.

WHAT IS NEW AND CONCLUSION

Haemodialysis reduces serum levetiracetam concentration and can lead to subtherapeutic levels. Close monitoring is necessary when dialysis is used on patients receiving anticonvulsant drugs that are extensively eliminated by the procedure.

Impact of Single Nucleotide Polymorphisms (SNPs) on Immunosuppressive Therapy in Lung Transplantation

Lung transplant patients present important variability in immunosuppressant blood concentrations during the first months after transplantation. Pharmacogenetics could explain part of this interindividual variability. We evaluated SNPs in genes that have previously shown correlations in other kinds of solid organ transplantation, namely ABCB1 and CYP3A5 genes with tacrolimus (Tac) and ABCC2, UGT1A9 and SLCO1B1 genes with mycophenolic acid (MPA), during the first six months after lung transplantation (51 patients). The genotype was correlated to the trough blood drug concentrations corrected for dose and body weight (C0/Dc). The ABCB1 variant in rs1045642 was associated with significantly higher Tac concentration, at six months post-transplantation (CT vs. CC). In the MPA analysis, CT patients in ABCC2 rs3740066 presented significantly lower blood concentrations than CC or TT, three months after transplantation. Other tendencies, confirming previously expected results, were found associated with the rest of studied SNPs. An interesting trend was recorded for the incidence of acute rejection according to NOD2/CARD15 rs2066844 (CT: 27.9%; CC: 12.5%). Relevant SNPs related to Tac and MPA in other solid organ transplants also seem to be related to the efficacy and safety of treatment in the complex setting of lung transplantation.

[Risk sharing agreements: with orphan drugs?]

OBJECTIVE

To summarize available information on share risk agreements (RSA) with orphan drugs (OD).

METHODS

A bibliographic search was carried out in MEDLINE, EMBASE and INAHTA using 19 keywords and combinations thereof. Papers published as original, narrative and systematic reviews, editorials, commentaries, letters to the Editor, and special articles were included and reviewed. Public or private institutional reports or documents found in Google that contained relevant information were also reviewed.

RESULTS

experience gained so far with RSA is scant. No published rigorous evaluations of outcomes of these agreements were found. It seems, however, that OD are suitable for introduction in clinical practice by means of RSA. There are two main types of RSA: financially based, and performance-outcome based. A number of theoretical advantages of SRA are described, as well as hurdles that hinder their design, implementation, and followup, and thus endangering their success. Very few RSA have clearly succeed so far.

CONCLUSIONS

If thoroughly managed, RSA may reasonably contribute to value-based pricing of OD, improve their pharmacovigilance, knowledge about their comparative effectiveness, and to reducing uncertainty and its consequences on patients, industry, payers and clinicians. There are technical groups that can bring the essential knowledge to manage RSA in Spain. The challenge now is to be able to harmonize their assessments and appraisals, to put in motion the mechanisms needed to overcome those hurdles, and to provide them adequate political and institutional support.

[Cefditoren pivoxil: A new oral cephalosporin for skin, soft tissue and respiratory tract infections]

Cefditoren pivoxil, a new-third generation cephalosporin antibiotic that has recently been granted approval in Spain, shows important activity over a large part of the pathogens causing skin, soft tissue and respiratory tract infections, including Gram-negative and Gram-positive bacteria. Cefditoren has also been shown to be stable against hydrolysis by many common beta-lactamases. Data from in vitro studies and clinical trials show this antibiotic as an oral formulation with an intrinsic activity against Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae equivalent to that of other third-generation cephalosporins administered via parenteral, like cefotaxime or ceftriaxone, thereby placing its maximal benefits mainly in the treatment of ambulatory infections. This paper reviews the main characteristics of cefditoren pivoxil (spectrum of activity, chemical structure, mechanism of action, pharmacokinetics, adverse effects and clinical efficacy) and attempts to find its place in current antibiotic therapeutics.

Phenolic constituents of Phenax angustifolius

Fractionation of an ethanolic extract of the leaves of Phenax angustifolius has resulted in the isolation of two new lignans, 2-hydroxy-2-(3',4'-dihydroxyphenyl)methyl-3-(3' ',4' '-dimethoxyphenyl)methyl-gamma-butyrolactone (1) and 2-hydroxy-2-(4'-O-beta-D-glucopyranosyl-3'-hydroxyphenyl)methyl-3-(3' ',4' '-dimethoxyphenyl)methyl-gamma-butyrolactone (2), and three known compounds, vitexin, isovitexin, and quercetin 3-O-alpha-L-rhamnopyranoside. The structures of 1 and 2 were determined using spectroscopic methods.

Therapeutic drug monitoring of tobramycin: once-daily versus twice-daily dosage schedules

OBJECTIVE

To evaluate the effect of dosage regimen (once-daily vs. twice-daily) of tobramicyn on steady-state serum concentrations and toxicity.

MATERIALS AND METHODS

Patients undergoing treatment with i.v. tobramycin (4 mg/kg/day) were randomised to two groups. Group OD (n = 22) received a once-daily dose of tobramycin and group TD (n = 21) received the same dose divided into two doses daily. Tobramycin serum concentrations (peak and trough) were measured by enzyme multiplied immunoassay. The renal and auditory functions of the patients were monitored before, during and immediately after treatment.

RESULTS

The two groups were comparable with respect to sex, age, body weight and renal function. No statistically significant differences were found in mean daily dose, duration of treatment, or cumulative dose. Trough concentrations were < 2 g/ml in the two groups (100%). Peak concentrations were > 6 microg/ml in 100% of the OD group and in 67% of the TD group (P< 0.01). Mean peak concentrations were markedly different: 11.00+/-2.89 microg/ml in OD vs. 6.53+/-1.45 microg/ml in TD (P< 0.01). The pharmacokinetics parameters were: Ke, (0.15+/-0.03/h in OD vs. 0.24+/-0.06/h in TD), t1/2, (4.95+/-1.41 h in OD vs. 3.07+/-0.71 h in TD), Vd (0.35+/-0.11 l/kg in OD vs. 0.33+/-0.09 l/kg in TD), Cl (0.86+/-0.29 ml/min/kg in OD vs. 1.28+/-0.33 ml/min/kg in TD). Increased serum creatinine was observed in 73% of patients in OD versus 57% of patients in TD, without evidence of nephrotoxicity. In TD group, three patients developed decreased auditory function, of which one presented with an auditory loss of -30 dB, whereas in the OD group only one patient presented decreased auditory function.

CONCLUSION

This small study suggests that a once-daily dosing regimen of tobramycin is at least as effective as and is no more and possibly less toxic than the twice-daily regimen. Using a single-dose therapy, peak concentration determination is not necessary, only trough samples should be monitored to ensure levels below 2 microg/ml.

Selection of optimal prophylactic aminoglycoside dosage in cancer patients: population pharmacokinetic approaches

We report an alternative dose-finding approach for the selection of optimal prophylactic aminoglycoside dosage in specific (sub)populations of patients. Relative a priori utility of several intervals of gentamicin or tobramycin (AMG) peak and trough serum levels were assigned by a group of pharmacokinetics experts, assuming prophylactic administration for laryngectomy interventions. A group of 27 adult patients, with normal renal function, undergoing elective surgery for laryngeal problems and treated prophylactically with gentamicin (80 mg t.i.d.) or tobramycin (100 mg t.i.d.) was studied. Two blood samples (peak and trough) were drawn at steady-state for AMG assay. Three different methods, standard two-stage (STS), extended least-squares non-linear regression [MULTI(ELS)] and non-parametric expected maximization (NEPM), were used to estimate the pharmacokinetic (PK) population parameters. PK simulations were applied to estimate the AMG steady-state concentrations from the PK population parameters. From these data, relative utility values were calculated, allowing the selection of the optimal dosage schedule for this group of patients. There were no statistically significant differences between the PK population estimates as generated by the three methods. Using the STS estimates, the simulation of several dosages indicated that the optimal dosage is 170 mg every 8 h. Conversely, using the individual PK parameters and the mean AMG levels simulated from them, the dose with best relative utility is 130 mg every 8 h. This important difference points out the relevance of the use of relative utilities for the AMG serum concentrations in the selection of optimal a priori dosage. We propose the use of 120 mg every 8 h as the safer dose for our population. Further studies are needed to validate this proposal in patients similar to ours.