Anti-calcitonin Gene-Related Peptide Monoclonal Antibodies in Migraine: Focus on Clinical Pharmacokinetics

The calcitonin gene-related peptide transmission was the target for recent development of drugs that effectively prevent attacks of both episodic and chronic migraine. The aim of this narrative review was to offer deeper insight into pharmacokinetics of monoclonal antibodies approved for prevention of migraine attacks. For this narrative review, relevant literature was searched for in MEDLINE and Google Scholar databases, covering periods 1966-2023 and 2006-2023, respectively. The ClinicalTrials.gov database was also searched for relevant clinical studies whose results had not been published previously in medical journals, covering the period 2000-2023. The monoclonal antibodies from this group are distributed mainly in the plasma and part of the extracellular space; they are neither metabolized in the liver nor excreted via the kidneys. The elimination of galcanezumab, eptinezumab and fremanezumab takes place only by a non-specific linear process via the reticuloendothelial system in the liver, while erenumab is eliminated by a non-specific process and by a specific, saturable process because of binding to receptors located on the cell membrane. Since the elimination processes do not have a large capacity, the half-life is about 2 weeks for erenumab and about 4 weeks for other monoclonal antibodies. Variability in the pharmacokinetics of these monoclonal antibodies is small in different subpopulations, and body weight is the only parameter to consider when choosing the dose of these drugs.

Anti-Calcitonin Gene-Related Peptide Monoclonal Antibodies in Migraine: Focus on Drug Interactions

Calcitonin gene-related peptide neurotransmission was the target for recent development of monoclonal antibodies that effectively prevent attacks of both episodic and chronic migraine. The aim of this narrative review was to offer deeper insight into drug-drug, drug-food and drug-disease interactions of monoclonal antibodies approved for prevention of migraine attacks. For this narrative review, relevant literature was searched for in MEDLINE and Google Scholar databases, covering the 1966-2023 and 2006-2023 periods, respectively. The ClinicalTrials.gov database was also searched for relevant clinical studies whose results had not been published previously in medical journals, covering 2000-2023. Monoclonal antibodies (erenumab, fremanezumab, galcanezumab and eptinezumab) augment prophylactic action of gepants and onabotulinumtoxin A and somewhat increase efficacy of triptans used to abort migraine attacks; however, their adverse reactions may also be augmented. Pharmacokinetic interactions and interactions in general with drugs used for other indications except migraine are negligible, as are drug-food interactions. However, monoclonal antibodies may worsen diseases with already weakened CGRP neurotransmission, Raynaud phenomenon and constipation. Monoclonal antibodies used for prevention of migraine do not engage in significant pharmacokinetic interactions with other drugs; however, they do engage in pharmacodynamic interactions with other anti-migraine drugs, additively augmenting their prophylactic action, but also increasing frequency and severity of adverse reactions, which are a consequence of the CGRP neurotransmission interruption.

Factors associated with hematological adverse reactions of drugs authorized via the centralized procedure

Serious hematological adverse drug reactions (HADRs) may lead to or prolong hospitalization and even cause death. The aim of this study was to determine the regulatory factors associated with HADRs caused by drugs that were authorized up to July 2023 by the European Medicines Agency (EMA) and to evaluate the frequency of HADRs. Using a cross-sectional approach, the type and frequency of HADRs were collected from the Summaries of Product Characteristics of Drugs Authorized by the EMA and analyzed within proprietary, nonproprietary, and biosimilar/biological frameworks. Multivariate statistical analysis was used to investigate the associations of generic status, biosimilar status, conditional approval, exceptional circumstances, accelerated assessment, orphan drug status, years on the market, administration route, and inclusion on the Essential Medicines List (EML) with HADRs. In total, 54.78% of proprietary drugs were associated with HADRs at any frequency, while anemia, leucopenia, and thrombocytopenia were observed in approximately 36% of the patients. The predictors of any HADR, anemia, and thrombocytopenia of any frequency are generic status, biosimilar status, and inclusion on the EML, while the only protective factor is the administration route. Biosimilars and their originator biologicals have similar frequencies of HADRs; the only exception is somatropin. Knowledge of the regulatory factors associated with HADRs could help clinicians address monitoring issues when new drugs are introduced for the treatment of patients.

Bioequivalence of Different Formulations of Zonisamide Oral Suspensions: A Short Review

To satisfy the needs of pediatric and other patients with focal onset seizures who cannot swallow solid dosage forms of zonisamide, an oral liquid form of this drug is necessary in clinical practice. Although there are two oral suspensions of zonisamide with marketing authorization (MA), there are issues of availability and high cost which limit their use and inspire extemporaneous compounding. Extemporaneously compounded oral suspensions of zonisamide are prepared according to different formulas and vary in stability; therefore it is essential to test this characteristic. Bioequivalence of extemporaneously compounded oral suspensions has never been tested, and the efficacy and safety of zonisamide oral suspensions have generally not been demonstrated in clinical trials. As a narrow therapeutic window drug, zonisamide requires precision in dosing, which could be achieved only with dosage forms with established bioavailability, efficacy, and safety. In order to avoid underdosing and toxicity with zonisamide oral suspensions and utilize their full therapeutic potential, it is necessary to perform bioequivalence studies with each variation of extemporaneously compounded oral suspension and also clinical trials with both commercial and extemporaneous oral suspensions of zonisamide.

Results of the trycort: Cohort study of add-on antihypertensives for treatment of resistant hypertension

Although true treatment resistant hypertension is relatively rare (about 7.3% of all patients with hypertension), optimal control of blood pressure is not achieved in every other patient due to suboptimal treatment or nonadherence. The aim of this study was to compare effectiveness, safety and tolerability of various add-on treatment options in adult patients with treatment resistant hypertension The study was designed as multi-center, prospective observational cohort study, which compared effectiveness and safety of various add-on treatment options in adult patients with treatment resistant hypertension. Both office and home blood pressure measures were recorded at baseline and then every month for 6 visits. The study cohort was composed of 515 patients (268 females and 247 males), with average age of 64.7 ± 10.8 years. The patients were switched from initial add-on therapy to more effective ones at each study visit. The blood pressure measured both at office and home below 140/90 mm Hg was achieved in 80% of patients with add-on spironolactone, while 88% of patients taking this drug also achieved decrease of systolic blood pressure for more than 10 mm Hg from baseline, and diastolic blood pressure for more than 5 mm Hg from baseline. Effectiveness of centrally acting antihypertensives as add-on therapy was inferior, achieving the study endpoints in <70% of patients. Adverse drug reactions were reported in 9 patients (1.7%), none of them serious. Incidence rate of hyperkalemia with spironolactone was 0.44%, and gynecomastia was found in 1 patient (0.22%). In conclusion, the most effective and safe add-on therapy of resistant hypertension were spironolactone alone and combination of spironolactone and a centrally acting antihypertensive drug.

Investigational new drugs for the treatment of Dravet syndrome: an update

INTRODUCTION

While there are already approved anticonvulsants for treatment of children with Dravet syndrome, disease modifying therapy is at its beginning.

AREAS COVERED

This narrative review is updating the latest information about efficacy and safety of both anticonvulsant and disease modifying investigational drugs for Dravet syndrome. Relevant publications were searched for in MEDLINE, GOOGLE SCHOLAR, SCINDEKS, and CLINICALTRIALS.GOV databases, from the dates of their foundation till January 2023.

EXPERT OPINION

The main advancements were made in the treatment of Dravet syndrome with confirmed haploinsufficiency of SCN1A gene. The application of antisense oligonucleotides has so far proven to be the most successful within disease-modifying therapy, but it also requires further refinement of the methodology of application and delivery to target cells, as well as additional testing of the effectiveness of antisense oligonucleotides outside of TANGO technology. Also, the full potential of gene therapy has yet to be explored, given that high capacity adenoviral vectors that can incorporate the SCN1A gene have recently been prepared.

Predictors of Mortality in Early Neonatal Sepsis: A Single-Center Experience

Background and Objectives: Early neonatal sepsis is associated with a significant mortality rate despite modern treatment strategies. Our aim was to identify risk factors contributing to the occurrence of death in newborns with early neonatal sepsis. Materials and Methods: We conducted a retrospective cross-sectional study that included newborns with early sepsis who received care in the intensive and semi-intensive care units at the Institute of Neonatology, Belgrade, Serbia. Newborns with early neonatal sepsis who died comprised the case group, whereas those who survived made up the control group. The diagnostic and therapeutic approach to the septic condition was carried out independently of this study, according to valid hospital protocols and current good practice guidelines. The influence of a large number of variables on the examined dichotomous outcome, as well as the mutual interaction of potential predictor variables, was examined by binary logistic regression. Results: The study included 133 pregnant women and 136 newborns with early neonatal sepsis, of which 51 (37.5%) died, while the remaining 85 newborns (62.5%) survived. Newborns who died had a statistically significantly lower birth weight compared to those who survived (882.8 ± 372.2 g vs. 1660.9 ± 721.1 g, p = 0.000). Additionally, compared to newborns who survived, among the deceased neonates there was a significantly higher proportion of extremely preterm newborns (74.5% vs. 22.4%, p = 0.000). The following risk factors for the occurrence of death in early neonatal sepsis were identified: low birth weight, sepsis caused by gram-negative bacteria, and the use of double-inotropic therapy and erythrocyte transfusion during the first week. Conclusions: Pediatricians should pay special attention to infants with early neonatal sepsis in whom any of the identified risk factors are present in order to prevent a fatal outcome.

Nonpharmaceutical interventions reduce the incidence and mortality of COVID‐19: A study based on the survey from the International COVID‐19 Research Network (ICRN)

The recently emerged novel coronavirus, “severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2),” caused a highly contagious disease called coronavirus disease 2019 (COVID‐19). It has severely damaged the world's most developed countries and has turned into a major threat for low‐ and middle‐income countries. Since its emergence in late 2019, medical interventions have been substantial, and most countries relied on public health measures collectively known as nonpharmaceutical interventions (NPIs). We aimed to centralize the accumulative knowledge of NPIs against COVID‐19 for each country under one worldwide consortium. International COVID‐19 Research Network collaborators developed a cross‐sectional online survey to assess the implications of NPIs and sanitary supply on the incidence and mortality of COVID‐19. The survey was conducted between January 1 and February 1, 2021, and participants from 92 countries/territories completed it. The association between NPIs, sanitation supplies, and incidence and mortality were examined by multivariate regression, with the log‐transformed value of population as an offset value. The majority of countries/territories applied several preventive strategies, including social distancing (100.0%), quarantine (100.0%), isolation (98.9%), and school closure (97.8%). Individual‐level preventive measures such as personal hygiene (100.0%) and wearing facial masks (94.6% at hospitals; 93.5% at mass transportation; 91.3% in mass gathering facilities) were also frequently applied. Quarantine at a designated place was negatively associated with incidence and mortality compared to home quarantine. Isolation at a designated place was also associated with reduced mortality compared to home isolation. Recommendations to use sanitizer for personal hygiene reduced incidence compared to the recommendation to use soap. Deprivation of masks was associated with increased incidence. Higher incidence and mortality were found in countries/territories with higher economic levels. Mask deprivation was pervasive regardless of economic level. NPIs against COVID‐19 such as using sanitizer, quarantine, and isolation can decrease the incidence and mortality of COVID‐19.

Acetaminophen toxicity and overdose: current understanding and future directions for NAC dosing regimens

INTRODUCTION

Although N-acetyl-cysteine (NAC) has long been used for the treatment of acetaminophen poisoning/overdose, the optimal NAC dosing regimen for varying patterns or severity of the poisoning/overdose is still unknown.

AREAS COVERED

Relevant literature was searched for in the MEDLINE (from 1964 until August 31^st, 2022), SCOPUS (from 2004 until August 31^st, 2022) and GOOGLE SCHOLAR (from 2004 until August 31^st, 2022) databases, without restriction in terms of publication date. The inclusion criteria were: original clinical studies reporting results, and studies investigating efficacy and safety of NAC dosing regimens in case(s) of overdose or poisoning with acetaminophen.

EXPERT OPINION

For a more effective treatment of acetaminophen poisoning in the future, it will be crucial to advance the technology of measuring acetaminophen, its metabolites and NAC in the serum, preferably with the point-of-care technique, so that in real time it can be continuously assessed whether it is necessary to administer NAC, and further to increase the dose of NAC and extend the duration of its administration, or not.

Cost-effectiveness of miglustat versus symptomatic therapy of Niemann-Pick disease type C

BACKGROUND

Niemann-Pick disease type C (NP-C) is a progressive neurodegenerative disorder with early infantile (< 2 years), late infantile (2-6 years), juvenile (7-15 years) and adolescent (> 15 years) onset. The mainstay of therapy for NP-C patients with neurological symptoms is miglustat, a drug that may modify the course of the disease.

AIM

Our aim was to evaluate the cost-effectiveness of miglustat in comparison to symptomatic therapy in patients with NP-C in the socio-economic settings of the Republic of Serbia, an upper-middle-income European economy.

METHOD

The perspective of the Serbian Republic Health Insurance Fund was chosen for this study, and the time horizon was eighty years. The main outcomes of the study were quality-adjusted life years gained with miglustat and comparator, and direct costs of treatment. The study was conducted through the generation and simulation of the Discrete-Event Simulation model. The model results were obtained after Monte Carlo microsimulation of a sample with 1000 virtual patients.

RESULTS

Treatment with miglustat was not cost-effective when compared with symptomatic therapy and was associated with negative values of net monetary benefit regardless of the onset of neurological manifestations (- 110,447,627.00 ± 701,614.00 RSD, - 343,871,695.00 ± 2,577,441.00 RSD, - 1,397,908,502.00 ± 23,084,235.00 RSD and - 2,953,680,879.00 ± 33,297,412.00 RSD) for early infantile, late infantile, juvenile and adolescent cohorts, respectively).

CONCLUSION

When traditional pharmacoeconomic evaluation is employed, miglustat is not a cost-effective option in comparison to symptomatic therapy for the treatment of NP-C. However, given the proven efficacy of miglustat, there is a need to find ways to make this drug available to all patients with NP-C.

Novel and emerging therapeutics for genetic epilepsies

INTRODUCTION

Disease-specific treatments are available only for a minority of patients with genetic epilepsies, while the rest are treated with anticonvulsants, which are ineffective in almost one-third of patients.

AREAS COVERED

Recently approved and the most effective emerging therapeutics under development for the treatment of genetic epilepsies are overviewed after systematic search and analysis of relevant literature.

EXPERT OPINION

New and emerging drugs for genetic epilepsies exploit one of the two approaches: inhibiting hyperactive brain foci through blocking excitatory or augmenting inhibitory neurotransmission, or correcting the underlying genetic defect. The first is limited by insufficient selectivity of available compounds, and the second by imperfection of currently used vectors of genetic material, unselective and transient transgene expression. Besides, the treatment may come too late, after structural abnormalities and epilepsy deterioration takes place. However, with recent improvements, we can expect to see soon gradual decline in the number of patients with therapy-resistant genetic epilepsies.

Personalization of drug dose thematic issue: introduction article

INTRODUCTION

The need to individualize a drug dosage and adjust it to a patient's physiological and/or pathophysiological status is rarely satisfied in routine clinical practice, primarily because of complexity of the adjustment task.

AREAS COVERED

The aim of this article is to shed light to basic principles of drug dosage individualization in the most frequent clinical states that affect pharmacokinetics of drugs. The principles are derived from published clinical studies conducted on diverse patient populations, using non-compartmental pharmacokinetic model.

EXPERT OPINION

Simple, but sufficiently exact, way to calculate appropriate drug dose for a patient is the one based on target average steady-state concentration and non-compartmental pharmacokinetic model. If target steady-state drug concentration and dosage interval are considered fixed, maintenance dose could be adjusted on the basis of expected changes of total drug clearance and bioavailability, while loading dose should be related to changes of volume of distribution and bioavailability. Relative increase or decrease of these pharmacokinetic parameters in regard to normal values in healthy persons is translated to relative (percentual) increase or decrease of maintenance and loading doses recommended in the drug monograph.

Risk factors for potential drug-drug interactions in patients with myasthenia gravis

OBJECTIVES

Our aim was to determine risk factors for and frequency of potential drug-drug interactions (pDDIs) among hospitalized patients with myasthenia gravis (MG).

METHODS

This was a retrospective cross-sectional study of the-first time hospitalized MG patients or patients hospitalized because of the exacerbation of MG at the Neurology Clinic of the Clinical Center of Serbia, Belgrade. Medical records and discharge summaries of hospitalized MG patients over a 10-year period were reviewed. The pDDIs were identified by means of Micromedex, and multivariate regression methods were used to reveal potential predictors of number of pDDIs per patient.

RESULTS

The study included 687 patients with MG. In total, 2041 pDDIs were detected in 608 (88.5%) patients. Among the discovered pDDIs, 329 different pDDIs were observed. The most frequent pDDIs were pyridostigmine-prednisone (487patients/70.9%) and aspirin-prednisone (90 patients/13.1%) classified as moderate, and enalapril-potassium chloride (71patients/10.3%) classified as major pDDI. Five drugs (aspirin, insulin, prednisone, cyclosporine, metformin) were responsible for 22.6% of different pDDIs. Dyspnea, generalized form of MG, diabetes mellitus, hypertension, total number of drugs-used, use of antiplatelets were identified as the relevant risk factors for total number of pDDIs (R2 = 0.626,F = 73.797, p < 0.001), while age of patients and history of cancer were inversely correlated with such an outcome.

CONCLUSION

The frequency of the pDDIs in hospitalized MG patients is high, and adversely influenced by dyspnea, generalized MG, diabetes mellitus, hypertension, total number of drugs-used and use of antiplatelets.

Experimental GABA A Receptor Agonists and Allosteric Modulators for the Treatment of Focal Epilepsy

GABA A receptors are ubiquitous in the central nervous system and there is a huge diversity of receptor subtypes in almost all regions of the brain. However, the expression of GABA A receptor subtypes is altered in both the gray and white matter of patients with focal epilepsy. Although there is a number of anticonvulsants with marketing authorization for the treatment of focal epilepsy which act through GABA A receptors, potentiating the inhibitory effects of GABA, it is necessary to develop more potent and more specific GABAergic anticonvulsants that are effective in drug-resistant patients with focal epilepsy. There are three orthosteric and at least seven allosteric agonist binding sites at the GABA A receptor. In experimental and clinical studies, full agonists of GABA A receptors showed a tendency to cause desensitization of the receptors, tolerance, and physical dependence; therefore, partial orthosteric agonists and positive allosteric modulators of GABA A receptors were further developed. Preclinical studies demonstrated the anticonvulsant efficacy of positive allosteric modulators with selective action on GABA A receptors with α2/α3 subunits, but only a handful of them were further tested in clinical trials. The best results were obtained for clobazam (already marketed), ganaxolone (in phase III trials), CVL-865 (in phase II trials), and padsevonil (in phase III trials). Several compounds with more selective action on GABA A receptors, perhaps only in certain brain regions, have the potential to become effective drugs against specific subtypes of focal-onset epilepsy. However, their development needs time, and in the near future we can expect only one or two new GABA A agonists to obtain marketing authorization for focal epilepsy, an advance that would be of use for just a fraction of patients with drug-resistant epilepsy.

A Critique of Pharmacokinetic Calculators for Drug Dosing Individualization

The 'one-dose-fits-all' approach where drug dosing regimen is prescribed according to recommendations from a summary of product characteristics is not appropriate for many patients whose clinical characteristics significantly differ from the most frequent ones in a population, as it cannot guarantee optimal exposure of target tissues to the drug. Our aim here is to provide a concise review of pharmacokinetic calculators currently available for clinical use and, at the same time, to suggest the minimum standards that they should satisfy to be routinely used in clinical practice. A systematic search of Medline, Ebsco, Scopus, Scindeks, Cochrane Library and Google Scholar was performed to find publications about available pharmacokinetic calculators for drug dose individualization. Theoretically well-founded and mathematically correct calculators for many drugs are available, but only a few calculators for specific drugs have been validated in clinical practice or through clinical trials, and the results published in peer-reviewed journals. The majority of available pharmacokinetic calculators for drug dosing individualization remain unvalidated, i.e., there is no evidence of their efficacy and safety in real-life clinical settings. Pharmacokinetic calculators for drug dose individualization are irreplaceable tools for achieving precision medicine, where dosing regimens are tailored to the needs and personal characteristics of each patient, maximizing efficacy and minimizing toxicity.

Lessons learned from the discovery of sodium valproate and what has this meant to future drug discovery efforts?

INTRODUCTION

The discovery of the anticonvulsant properties of valproic acid and the development of valproic acid/valproate to market authorization for specific epilepsy types and syndromes, as well as their repurposing for other indications, are illustrative examples of both the strengths and weaknesses of drug development strategies.

AREAS COVERED

This review summarizes and interprets the development and repurposing history of valproic acid/valproate. The article is based on articles, including original studies and systematic reviews obtained from PubMed, Scopus, EBSCO, SCIndeks and Google Scholar databases.

EXPERT OPINION

Random screening and careful observation of the experimental effects of tested substances were crucial for discovering the anticonvulsant effects of valproic acid, while rational drug design and clinical observation strategies led to repurposing valproic acid and valproate for bipolar disorder maintenance treatmentand prevention of migraine attacks. Early planning and feasibility studies of future clinical trials are essential for obtaining marketing authorization of new substances or new indications of old anticonvulsants. Significant progress has been made recently toward understanding, treatment and prevention of hepatotoxicity caused by valproic acid/valproate, making its long-term administration safer. There are ongoing efforts to repurpose valproic acid/valproate for augmentation with antipsychotic drugs for the treatment of schizophrenia.

Population pharmacokinetic analysis of bisoprolol in type 2 diabetic patients with hypertension

PURPOSE

Given that it has been reported that type 2 diabetes mellitus may affect the pharmacokinetics of a large number of drugs and that there are still no published population pharmacokinetic (PopPK) analyses in routinely treated patients with hypertension and type 2 diabetes mellitus as comorbid condition, the aim of this study was to determine PK variability of bisoprolol in 70 Serbian patients using the PopPK approach.

METHODS

PopPK analysis was conducted using a nonlinear mixed effects model (NONMEM), version 7.3.0 (Icon Development Solutions). In our patients, a total daily dose of bisoprolol ranged from 1.25 to 10 mg. The drug was administrated orally as a single daily dose or in two divided doses per day.

RESULTS

A wide range of the drug concentrations were noted (1-103 ng/mL) in the population consisted of the adult patients with type 2 diabetes mellitus. From a total of 21 separately assessed covariates, our results indicated that only creatinine clearance could have a potential impact on the variability of the clearance of bisoprolol.

CONCLUSION

Routine assessment of renal function should be carried out before the initiation of treatment with bisoprolol in order to individualize the dose and to prevent possible accumulation and adverse drug reactions.

Antimicrobial treatment of Stenotrophomonas maltophilia invasive infections: Systematic review

Stenotrophomonas maltophilia can cause serious infections in immunocompromised patients. The aim of this systematic review was to establish what invasive infections in humans are caused by S. maltophilia and to evaluate the optimal choice of antibiotics for their treatment. MEDLINE, EBSCO, SCOPUS, SCINDEKS and GOOGLE SCHOLAR were systematically searched for clinical trials, observational studies, case reports or case series describing invasive infections with S. maltophilia in patients of any age. S. maltophilia may cause invasive infections of various tissues in hospitalized patients. In the great majority of cases it was susceptible to co-trimoxazole, levofloxacin and ceftazidime. In about three fourths of the cases, the treatment was successful, while less than 20% of the patients died. S. maltophilia is increasingly associated with serious invasive infections in hospitalized patients and due to growing trend of resistance to almost all antibiotics requires a careful approach to patients who is harboring this bacterium.

Cost-utility of tafenoquine vs. primaquine for the radical cure (prevention of relapse) of Plasmodium vivax malaria

The aim of this study was to compare cost-utility of tafenoquine (TQ) and primaquine (PQ) for a radical cure (prevention of relapse) of Plasmodium vivax (PV) malaria in Serbia using A five-state, 1-month cycle Markov model. The perspective of Republic Health Insurance Fund was chosen, and the time horizon was 10 years. The model results were obtained after Monte Carlo microsimulation of a sample with 1000 virtual patients. After base case analysis PQ was dominated by TQ, as the net monetary benefit was positive (20,713.84 ± 7,167.46 RSD (99% CI) (174.95 ± 60.54 €)) and incremental cost-effectiveness ratio was below the willingness-to-pay line of 1 Serbian gross national product per capita per quality-adjusted life year gained. Multiple one-way sensitivity analysis and probabilistic sensitivity analysis confirmed the results of the base case simulation. In conclusion, TQ was cost-effective in comparison to PQ for radical cure of PV malaria in socio-economic settings of a South-Eastern European country.

Screening general practice patients for migraine without aura: construction and validation of the Balkan Migraine Screening Questionnaire (BMSQ)

Aim To develop and validate a screening questionnaire for migraine without aura with sufficient diagnostic accuracy to be used in primary care settings. Methods The study was designed as cross-sectional, multicentric, diagnostic accuracy trial of new questionnaire for screening patients who visit general practitioners, with an aim to reveal migraine without aura. The instrument was constructed for the purpose of this study, and validated on the sample of 429 primary care outpatients. The gold standard of diagnosing migraine without aura was clinical estimate by a neurologist based on the International Classification of Headache Disorders 3rd edition (ICHD-III) criteria. Diagnostic accuracy of the instrument was tested through construction of the Receiver Operator Curve. Results The Balkan Migraine Screening Questionnaire (BMSQ) instrument showed good diagnostic accuracy (sensitivity 83.4% and specificity 79.9%) for migraine without aura, with significant screening yield among previously undiagnosed patients of 75.9%. The study also confirmed a high percentage of patients with hidden migraine without aura (MWA) (52.9%) revealed by the BMSQ and the ICHD-III criteria that would otherwise remain undiagnosed. Conclusion The BMSQ is a valid and reliable clinical instrument for revealing migraine without aura, which could be easily selfadministered by patients. It has high screening yield, discovering majority of patients with previously undiagnosed migraine without aura, whose definite diagnosis should later on be confirmed by the attending physicians using the ICHD-III criteria.

Clinical Pharmacokinetics of Second-Generation Triazoles for the Treatment of Invasive Aspergillosis and Candidiasis

Second-generation triazoles were developed in response to the quest for more efficacious and safer therapeutic options for the treatment of severe systemic aspergillosis and candidiasis. These agents include voriconazole, posaconazole, isavuconazole, and ravuconazole. The aim of this review was to present and compare the pharmacokinetic characteristics of second-generation triazoles for the treatment of invasive aspergillosis and candidiasis, emphasizing their clinical implications. The MEDLINE, Scopus, EBSCO, Google Scholar, and SCIndeks databases were searched using advanced search options, including the names of second-generation triazoles and pharmacokinetic terms as keywords. The intravenous administration of voriconazole, posaconazole, and isavuconazole results in stable pharmacokinetics of these drugs, with mostly predictable variations influenced by common and usually known factors in routine clinical settings. The high oral bioavailability of isavuconazole and, to some extent, voriconazole makes them suitable for intravenous-to-oral switch strategies. Except for intravenous voriconazole (due to the accumulation of the toxic vehicle hydroxypropyl betadex), dose reduction of second-generation triazoles is not needed in patients with renal failure; patients with hepatic insufficiency require dose reduction only in advanced disease stages. The introduction of therapeutic drug monitoring could aid attempts to optimize the blood concentrations of triazoles and other drugs that are known to or that possibly interact, thus increasing treatment efficacy and safety. There is a need for new studies that are designed to provide useful data on second-generation triazole pharmacokinetics, particularly in special circumstances such as central nervous system and ocular infections, infections in newborns and infants, and in subjects with genetic polymorphisms of metabolizing enzymes.

Pharmacoeconomic Aspects of Low Back Pain Treatment: Cost of Illness Study in the Republic of Serbia

INTRODUCTION

Chronic diseases with disabilities have a huge pharmacoeconomic impact on the health budget, especially in countries with recent history of social and economic transition. The aim of this study was to identify total costs of treating patients with lumbar pain in medical facilities in the central part of the Republic of Serbia.

MATERIAL AND METHODS

This study was designed as a cost of illness study, using a bottom-up approach and it was conducted from a societal perspective. This study included 97 patients with lumbar syndrome who were treated in outpatient facilities in the Central part of Serbia.

RESULTS

Total costs of treating lumbar pain were about €200.40 ± €86.65 per patient per year, where the largest volume of direct costs were costs due to visits to specialists in primary health care institutions (€9.39 ± €6.66). Total indirect costs were €182.00 ± €78.66.

DISCUSSION

Our findings highlight the need to estimate the total costs of treating lumbar pain and evaluate the correlation between costs and other variables for larger population of these patients.

CONCLUSION

This study distinguished two important pharmacoeconomic aspects of treating lumbar pain. Firstly, indirect costs represent major part of total costs of treating lumbar syndrome. Secondly, differences in valuing medical services between countries with recent history of social and economic transition and countries within European Union are one of crucial reasons for difference in total costs of treating low back pain among patients in neighboring regions.

Drug-drug interactions in patients with acute coronary syndrome across phases of treatment

The objective of this study is to evaluate potential drug-drug interactions (pDDIs) and risk factors for pDDIs in three phases of an acute coronary syndrome (ACS) treatment: from the point of first medical contact to the coronary angiography (first phase), after coronary angiography to the last day of hospitalization (second phase), and at discharge from hospital (third phase). This retrospective observational cohort clinical study was conducted at the Clinic for Cardiology of the Clinical Centre Kragujevac, a public tertiary care hospital in Kragujevac, Serbia. Micromedex^® interaction checker was used to detect pDDIs. This study included 245 ACS patients. All patients were exposed to at least one pDDI in all the phases of treatment. Mean total number of pDDIs was 9.47 ± 6.07, 10.11 ± 6.92, and 6.29 ± 3.66 in first, second, and third phases, respectively. Age, > 6 h from the beginning of the symptoms to admission, primary PCI, STE-ACS, COPD, delirium, hyperlipidemia, hypertension, obesity, systolic blood pressure at admission, TIMI risk score at admission, ALT, LDL, number of physicians who prescribed drugs to a single patient, number of prescribed drugs, and various pharmacological classes increased risk of pDDIs. Mechanical ventilation, dementia, and drug allergy noted in the medical documentation protected against them. Effects of heart failure, diabetes, and aPTT depended on phase of treatment and severity of pDDI. In conclusion, physicians should be vigilant to the possibility of pDDIs in patients harbouring factors that may increase their rate.

Drug-drug interactions in patients receiving hematopoietic stem cell transplantation

INTRODUCTION

Recipients of hematopoietic stem cell transplantation (HSCT) are exposed to numerous drugs in both pre- and post-transplantation period, which creates an opportunity for drug-drug interactions (DDIs); if clinically relevant DDIs happen, the risk of adverse treatment outcomes is increased. Areas covered: This review is focused on DDIs in recipients of HSCT that were observed and published as clinical trials, case series or case reports. Relevant publications were found by the systematic search of the following online databases: MEDLINE, SCOPUS, EBSCO, and SCINDEX. Expert opinion: The most important DDIs involve cytostatic or immunosuppressant drug on one side, and antimicrobial drugs on the other. The majority of clinically relevant interactions have pharmacokinetic character, involving drug metabolizing enzymes in the liver. Antifungal azoles inhibit metabolism of many cytostatic and immunosuppressant drugs at cytochromes and increase their plasma concentrations. Macrolide antibiotics and fluoroqunolones should be avoided in HSCT recipients, as they have much larger potential for DDIs than other antibiotic groups. HSCT recipients increasingly receive new immunomodulating drugs, and further observational studies are needed to reveal unsuspected DDIs with clinical relevance.

Clinical Application of Pharmacokinetics: Basis for Rational Dose Selection in a Critically Ill Patient on Renal Replacement Therapy

BACKGROUND

Individualizing drug dosing regimens in critically ill patients on renal replacement therapy is a challenge to clinicians as guidelines are often imprecise and specific-validated pharmacokinetic software is unavailable.

OBJECTIVE

A case of a septic patient on hemodialysis is presented, where a quick solution for antibiotic dose adjustment based on the application of pharmacokinetic principles was found.

METHODS

The dose adjustment was made in two steps-the first step was to calculate total antibiotic clearance (using the formula: total drug clearance = dialysate flow rate × fraction of unbound drug in plasma + extrarenal clearance), and the second step was to calculate maintenance dose based on target plasma concentrations in steady-state (using the formula: maintenance dose = target plasma concentration × total drug clearance × dose interval).

RESULTS

After the doses of antibiotics were adjusted, the patient's condition gradually improved, with a drop in body temperature to normal values, a decrease in plasma levels of inflammatory parameters, and the emergence of spontaneous diuresis. The plasma concentration of vancomycin was within the recommended therapeutic range.

CONCLUSIONS

Specific pharmacokinetic software and measuring plasma concentrations of the drugs should be used for calculation of total drug clearance and dose adjustment whenever possible. However, if unavailable, basic pharmacokinetic formulas and principles could be successfully used instead to adjust the dose in critically ill patients on hemodialysis.

Profile of evolocumab and its cost-effectiveness in patients with high cardiovascular risk: literature review

INTRODUCTION

Evolocumab is fully human monoclonal antibody which binds to proprotein convertase subtilisin/kexin type 9 (PCSK9), and prevents its blocking effect on recycling of liver low-density lipoprotein (LDL) receptors. Areas covered: The aim of this review is to assess efficacy, safety, and cost-effectiveness of evolocumab in adult patients with high cardiovascular risk. Major research databases MEDLINE, EBSCO, and CENTRAL were systematically searched for relevant study reports. Expert commentary: Even when given in full doses, statins augmented with ezetimibe and cholesterol-binding resins could not reduce cholesterol baseline level for more than 66%, while evolocumab reduces cholesterol level for 75% or even more. Up to now, evolocumab showed good safety profile, and patents tolerate it very well. The abovementioned advantages of evolocumab made it almost ideal drug for hypercholesterolemia, and probably in the future the best drug for secondary prevention of major cardiovascular events. Evolocumab is borderline cost-effective for the treatment of patients with high cardiovascular risk in European countries, while in the U.S.A. it is under debate where the underlying assumption (risk of cardiovascular disease events) determine the true value.

The first comparative double-blind trial on efficacy and safety of ergotamine based five-component combination and sumatriptan in migraine without aura

BACKGROUND

Dihydroergotamine or ergotamine are the most effective preparations for aborting acute attacks of migraine without aura.

OBJECTIVE

The aim of our study was to compare the efficacy and safety of ergotamine based five-component drug combination and sumatriptan in the treatment of moderate to severe acute attacks of migraine without aura.

METHODS

The study was designed as a randomized, double-blind, double-dummy, placebo-controlled, parallel arm, multi-center clinical trial. The enrolled patients having migraine without aura were randomized to one of the study arms, ergotamine based five-component drug combination or sumatriptan.

RESULTS

In total, 201 patients were randomized to one of the treatment arms. Higher percentage of patients was completely free of the headache two hours after dose administration in the ergotamine-based medication group compared to the sumatriptan group, regardless whether all (51.12 % vs 33.70 %) or only repeated attacks were taken into account (50.91 % vs 23.73 %); the salvage therapy (diclofenac) utilization rate was also lower in the ergotamine-based medication group (relative risk 0.61). Photophobia, phonophobia, and osmophobia were reversed more frequently in the ergotamine-based medication group (51.12 % vs 33.70 %), and failure to abort an attack of the migraine without aura occurred more frequently in the group treated with sumatriptan (1.1 % vs 4.9 %). The headache intensity two hours after ingestion of the study medication increased more frequently with sumatriptan, while other adverse events were rare in both groups.

CONCLUSIONS

This study demonstrated higher efficacy and similar safety of ergotamine based fixed drug combination in comparison to sumatriptan, when used in the treatment of an acute attack of the migraine. HIPPOKRATIA 2018, 22(1): 17-22.

Pharmacodynamics and common drug-drug interactions of the third-generation antiepileptic drugs

INTRODUCTION

Anticonvulsants that belong to the third generation are considered as 'newer' antiepileptic drugs, including: eslicarbazepine acetate, lacosamide, perampanel, brivaracetam, rufinamide and stiripentol. Areas covered: This article reviews pharmacodynamics (i.e. mechanisms of action) and clinically relevant drug-drug interactions of the third-generation antiepileptic drugs. Expert opinion: Newer antiepileptic drugs have mechanisms of action which are not shared with the first and the second generation anticonvulsants, like inhibition of neurotransmitters release, blocking receptors for excitatory amino acids and new ways of sodium channel inactivation. New mechanisms of action increase chances of controlling forms of epilepsy resistant to older anticonvulsants. Important advantage of the third-generation anticonvulsants could be their little propensity for interactions with both antiepileptic and other drugs observed until now, making prescribing much easier and safer. However, this may change with new studies specifically designed to discover drug-drug interactions. Although the third-generation antiepileptic drugs enlarged therapeutic palette against epilepsy, 20-30% of patients with epilepsy is still treatment-resistant and need new pharmacological approach. There is great need to explore all molecular targets that may directly or indirectly be involved in generation of seizures, so a number of candidate compounds for even newer anticonvulsants could be generated.

Risk factors for potential drug-drug interactions in intensive care unit patients

PURPOSE

To determine risk factors for each severity-based category of potential drug-drug interactions (DDIs) encountered at intensive care unit (ICU) patients.

METHODS

This was a retrospective cohort analysis of patients treated at the ICU of the Clinical Center Kragujevac, a public tertiary care hospital in Kragujevac, Serbia. Three interaction checkers were used to reveal drug-drug interactions: Medscape, Epocrates and Micromedex.

RESULTS

The study included 201 patients, 66.19±16.11 years of age. Average number of DDIs per patient ranged from 10.49±8.80 (Micromedex) to 29.43±21.51 (Medscape). Antiarrhythmic or anticonvulsant drug prescription, Charlson Comorbidity Index, male sex, length of hospitalization, number of drugs or therapeutic groups prescribed and surgery increased the risk of DDIs in ICU patients, while presence of delirium or dementia and transfer from emergency department to ICU protected against.

CONCLUSIONS

The rate of the DDIs in ICU patients at a tertiary care hospital is high, and adversely influenced by number of drugs or drug groups prescribed per patient, antiarrhythmic or anticonvulsant drug prescription, comorbidities, length of hospitalization and surgery. On the other hand, presence of cognitive deficit and transfer from emergency department to ICU protect ICU patients from the DDIs.

Evaluation of brivaracetam: a new drug to treat epilepsy

INTRODUCTION

High prevalence of therapy-resistant epilepsy demands development of anticonvulsants with new mechanisms of action. Brivaracetam is an analogue of levetiracetam which binds to the synaptic vesicle protein 2A (SV2A) and decreases release of excitatory neurotransmitters. Areas covered: Relevant published studies were searched for by predefined strategy in MEDLINE, EBSCO and SCINDEKS electronic databases. Brivaracetam is effective as adjunctive therapy for uncontrolled partial-onset seizures with or without secondary generalization in patients 16 years and older with epilepsy. It reduces baseline-adjusted focal seizure frequency per week from 7.3 to 12.8% over placebo. Adverse events rate in patients with brivaracetam is not higher than in patients with placebo. Expert opinion: Brivaracetam is an important step forward in the treatment of therapy-resistant partial-onset seizures with or without secondary generalization. Its development was systematic and targeted. Due to its efficacy and excellent safety profile, it is likely that brivaracetam will be often prescribed. In future, efficacy and safety of brivaracetam should be tested in monotherapy settings and also in the first-line therapy of partial-onset seizures.

Translation and Validation of the Serbian Version of the Skindex-29 Instrument for Measuring Impact of Skin Disease on Quality of Life

The Skindex-29 instrument, which is intended for measuring the influence of skin diseases on quality of life, was developed and validated in several languages. However, a Serbian translation of the instrument is not available. The aim of this study was to translate the Skindex-29 from English to Serbian, to make necessary cultural adaptations, and to test its psychometric properties in a sample of outpatients with various skin diseases. The Skindex-29 was translated and adapted according to internationally accepted guidelines and then tested on a sample of Serbian outpatients with various skin diseases. Internal consistency was checked through calculation of Cronbach's alpha and Interclass Correlation Coefficient for the instrument's domains. The criterion validity of the translation was tested by correlating scores of domains with scores on the Serbian version of Dermatological Life Quality Index (DLQI).Validity of the construct was tested through comparison of the domains scores in groups of patients with different skin diseases. Fifty-three patients (18.6%) suffered from acne vulgaris, 48 (16.8%) from verrucae vulgares, 40 (14.0%) from psoriasis, 34 (11.9%) from an undetermined type of mild dermatitis, 20 (7.0%) from venous ulcers, 19 (6.7%) from eczema, and 71 (24.9%) from other skin diseases. The Serbian translation of Skindex-29 showed good internal consistency: Cronbach's alpha for Emotional, Symptoms, and Functioning domains was 0.885, 0.752, and 0.901, respectively. Validity of the instrument in all aspects (criterion, content, and construct validity) was satisfactory, yet the Symptoms domain could not discriminate well between more and less severe skin diseases. The Serbian translation of Skindex-29 appears to be a reliable and valid specific instrument for measuring the adverse influence of skin diseases on quality of life.

Inflammatory Bowel Diseases (Crohn´s Disease and Ulcerative Colitis): Cost of Treatment in Serbia and the Implications

BACKGROUND

Although the costs of treating inflammatory bowel disease (IBD) in developed countries are well established, they remain largely unknown in countries with recent histories of socio-economic transition including Serbia.

OBJECTIVE

To estimate the costs of treatment including the resources used by patients with IBD in Serbia from a societal perspective. This includes both Crohn's disease and ulcerative colitis.

METHODS

This cost-of-illness study was conducted to identify direct, indirect and out-of-pocket costs of treating patients with IBD in Serbia. Patients with IBD (n = 112) completed a semi-structured questionnaire with data concerning their utilisation of heath-care resources and illness-related expenditures. All costs were calculated in Republic of Serbia dinars (RSD) at a 1-year level (2014) and subsequently converted to Euros. Median values and ranges were reported to avoid potential distortions associated with mean costs.

RESULTS

Median total direct costs and total indirect costs per patient per year in patients with Crohn's disease were 192,614.32RSD (€1602.97) and 28,014.00RSD (€233.13) and 142,267.15RSD (€1183.97) and 21,436.00RSD (€178.39), respectively, in patients with ulcerative colitis. In both groups, the greatest component of direct costs was hospitalisation.

CONCLUSIONS

Costs of IBD in Serbia are lower than in more developed countries for two reasons. These include the fact that expensive biological therapy is currently under-utilised in Serbia and prices of health services are largely controlled by the State at a low level. The under-utilisation of biologicals may change with the advent of biosimilars at increasingly lower prices.

Measuring Potential of Preschool Facility Staff to Prevent Early Childhood Caries

The aim of this study was to investigate the possible potential of preschool staff through a newly designed questionnaire and evaluate their role in the prevention of early childhood caries (EEC) in Serbia where extremely high prevalence of this preventable disease was recorded.

We preformed a cross-sectional study of 268 preschool staff using specially prepared semi-structured questionnaire for measuring potential of secondary children’s caregivers to prevent EEC. The questionnaire was tested on a pilot sample and after that all collected data were analyzed trough construction of correlation matrix with the evaluation of the value of each question, reliability testing, factorial analysis and estimating of its validity using SPSS software.

The tested questionnaire had good internal consistency based on the Cronbach’s alpha coefficient value of 0.873 calculated directly and similar value (0.899) after applied Spearman-Brown “prediction” formula. Using exploratory factorial analysis and orthogonal rotation, we identified two domains that emerged with similar loadings (4.043 and 3.183). The first factor (domain) reflected attitudes of the study participants towards prevention of EEC, and the second factor (domain) showed behaviour of the study participants, which includes preventive actions against EEC.

The total score of the questionnaire was correlated positively with oral health knowledge (Spearman’s correlation coefficient 0.331, p=000) and inversely with the length of employment, where each additional year of employment decreased the total score of the questionnaire by 1.20.

These findings could partially explain an extremely high prevalence of EEC in young children and indicate that preschool teachers should be more engaged in health education activities and motivation programs.

Cost-Effectiveness of Introducing Point-of-Care Test for Detection of Level of Glycogen Phosphorylase in Early Diagnostic Algorithm of Acute Coronary Syndrome

BACKGROUND

The detection of specific biomarkers in the early phase of acute coronary syndrome (ACS) is important for the early diagnosis and appropriate management of patients with ACS.

OBJECTIVES

To estimate the cost-effectiveness of introducing a diagnostic point-of-care (POC) test for determining the levels of glycogen phosphorylase BB isoform (GPBB) in a standard diagnostic algorithm for the early diagnosis of ACS within the health system of the Republic of Serbia.

METHODS

The probabilistic decision-tree model was constructed for patients with nontraumatic chest pain comparing the use of standard diagnostic procedure, physical examination, and electrocardiogram monitoring with the use of a diagnostic test for the detection of the levels of specific biomarkers. The perspective of the health care services purchaser (the Republic Institute for Health Insurance, Serbia) was used in the model, and only direct costs were taken into account. The time horizon was set at one treatment episode of ACS, and the discount rate was not included because of the short length of the time horizon.

RESULTS

Using the GPBB POC test in comparison with not using it in the early diagnosis of ACS results in a significant reduction in the cost per treatment episode (10,034.48 ± 7,283.80 Serbian dinar [RSD]), increase in the number of survivors per 1000 treatment episodes (16 ± 18), decrease in the number of hospitalizations per 1000 treatment episodes (104 ± 44), and decrease in the number of performed coronarographies per 1000 treatment episodes (22 ± 19). The costs per hospitalization avoided (incremental cost-effectiveness ratio) were -145,887.57 ± 5,271.54 RSD, and the costs per coronarography avoided were -137,295.68 ± 4,681.05 RSD.

CONCLUSIONS

In the circumstances of limited health resources, reducing hospitalizations and decreasing unnecessary treatments and invasive diagnostic procedures by a GPBB POC test could be an effective way to improve the economic status of other Balkan countries with limited health care budgets.

Risk factors for healthcare-acquired urinary tract infections caused by multi-drug resistant microorganisms

INTRODUCTION

Healthcare-acquired urinary tract infections (HAUTI) make up to 40% of all healthcareacquired infections and contribute significantly to hospital morbidity, mortality, and overall cost of treatment.

OBJECTIVE

The aim of our study was to investigate possible risk factors for development of HAUTI caused by multi-drug resistant pathogens.

METHODS

The prospective case-control study in a large tertiary-care hospital was conducted during a five-year period. The cases were patients with HAUTI caused by multi-drug resistant (MDR) pathogens, and the controls were patients with HAUTI caused by non-MDR pathogens.

RESULTS

There were 562 (62.6%) patients with MDR isolates and 336 (37.4%) patients with non-MDR isolates in the study. There were four significant predictors of HAUTI caused by MDR pathogens: hospitalization before insertion of urinary catheter for more than eight days (ORadjusted = 2.763; 95% CI = 1.352–5.647; p = 0.005), hospitalization for more than 15 days (ORadjusted = 2.144; 95% CI = 1.547–2.970; p < 0.001), previous stay in another department (intensive care units, other wards or hospitals) (ORadjusted = 2.147; 95% CI = 1.585–2.908; p < 0.001), and cancer of various localizations (ORadjusted = 2.313; 95% CI = 1.255–4.262; p = 0.007).

CONCLUSION

Early removal of urinary catheter and reduction of time spent in a hospital or in an ICU could contribute to a decrease in the rate of HAUTI caused by MDR pathogens.

Cost-Effectiveness Comparison of Fidaxomicin and Vancomycin for Treatment of Clostridium difficile Infection: A Markov Model Based on Data from a South West Balkan Country in Socioeconomic Transition

BACKGROUND

Recent studies have shown that fidaxomicin, a novel antibiotic, can reduce the rate of complications and mortality in patients with colitis induced by Clostridium difficile. Introduction of fidaxomicin in clinical practice is limited by its high costs.

OBJECTIVES

The purpose of this study was to estimate the cost effectiveness of using fidaxomicin versus vancomycin in patients with colitis induced by C. difficile who did not respond to oral metronidazole.

METHODS

We constructed a Markov model that was than simulated by Monte-Carlo simulation using 1000 virtual patients with colitis induced by C. difficile. The perspective in our model was institutional. The time horizon was 3 months. Values of transition probabilities and therapy outcomes were estimated from the available literature, the prices of health services were obtained from the Republic Institute for Health Insurance Tariff Book, and the price of fidaxomicin was derived from data gained from the drug manufacturer.

RESULTS

The total costs of treating one statistical patient for 3 months with fidaxomicin were higher (48,106.19 ± 118.07 Republic of Serbia dinars [RSD]; 95% confidence interval 47,988.12-48,224.27) than the total costs of treating with vancomycin (25,872.85 ± 41.44 RSD; 95% confidence interval 25,831.41-25,914.29). Our results showed that the treatment of infections induced by C. difficile with fidaxomicin correlated with a lower rate of mortality and with a smaller number of colectomies. The incremental cost-effectiveness ratio of fidaxomicin versus vancomycin for colitis induced by C. difficile per saved life was estimated at 2.97 million RSD and for one avoided colectomy at 10.07 million RSD.

CONCLUSIONS

Results of our model indicate that fidaxomicin is a cost-effective therapy compared with vancomycin in patients with colitis induced by C. difficile if the outcome is life-year saved. However, if the outcome is the number of avoided colectomies, then fidaxomycin is not a cost-effective option compared with vancomycin.