Classification of recombinant factor VIII products and implications for clinical practice: A systematic literature review

INTRODUCTION

Consensus over the definition of recombinant factor VIII (rFVIII) product classification in haemophilia A is lacking. rFVIII products are often classified as standard half-life (SHL) or extended half-life (EHL); despite this, no universally accepted definition currently exists. One proposed definition includes half-life, area under the curve, and technology designed to extend half-life; however, the International Society on Thrombosis and Haemostasis defines activity over time as the most intuitive information for building treatment regimens and the World Federation of Hemophilia describes rFVIII product classification in terms of infusion frequency.

AIM

To summarise published data on the clinical and pharmacokinetic criteria used to define rFVIII product classification.

METHODS

PubMed and EMBASE database searches of English-language articles (2002-2022) were conducted using search strings to identify the relevant population, intervention, and outcomes (e.g., clinical and pharmacokinetic parameters). Articles then underwent title/abstract and full-text screens.

RESULTS

Among 1147 identified articles, 62 were included. Half-life was the most widely reported outcome with no clear trends or product groupings observed. No clear groupings emerged among other outcomes, including infusion frequency, consumption, and efficacy. As activity over time was reported in few articles, further investigation of its relevance to rFVIII product classification is warranted.

CONCLUSION

The findings of this systematic literature review suggest that parameters other than half-life might be important for the development of a comprehensive and clinically relevant rFVIII product classification definition. There seems to be an opportunity to consider parameters that are clinically meaningful and useful for shared decision-making in haemophilia A treatment.

A French Real-World Evidence Study Evaluating the Efficacy, Safety, and Pharmacokinetic Parameters of rVIII-SingleChain in Patients with Hemophilia A Receiving Prophylaxis

BACKGROUND

 rVIII-SingleChain is a recombinant factor VIII (FVIII) with increased binding affinity to von Willebrand factor compared with other FVIII products. rVIII-SingleChain is indicated for the treatment and prevention of bleeding episodes in patients with hemophilia A.

OBJECTIVES

 To collect real-world evidence data from patients treated with rVIII-SingleChain to confirm the efficacy and safety established in the clinical trial program and carry out a population pharmacokinetic (PK) analysis.

PATIENTS/METHODS

 This interim analysis includes data, collected between January 2018 - September 2021, from patients treated with rVIII-SingleChain prophylaxis at French Hemophilia Treatment centers. Data on annualized bleeding rates, dosing frequency, and consumption before and after switching to rVIII-SingleChain were recorded. A population PK analysis was also conducted to estimate PK parameters.

RESULTS

 Overall, 43 patients switched to prophylaxis with rVIII-SingleChain either from a previous prophylaxis regimen or from on-demand treatment. Following the switch to rVIII-SingleChain, patients maintained excellent bleed control. After switching to rVIII-SingleChain, most patients maintained or reduced their regimen. Interestingly, a majority of patients treated >2 ×/weekly with a standard half-life FVIII reduced both injection frequency and FVIII consumption with rVIII-SingleChain. A PK analysis revealed a lower clearance of rVIII-SingleChain (1.9 vs. 2.1 dL/h) and a longer half-life both in adolescents/adults (n = 28) and pediatric (n = 6) patients (15.5 and 11.9 hours, respectively vs. 14.5 and 10.3 hours) than previously reported.

CONCLUSIONS

 Patients who switched to rVIII-SingleChain prophylaxis demonstrated excellent bleed control and a reduction in infusion frequency. A population PK analysis revealed improved PK parameters compared with those reported in the clinical trial.

Clinical experience of switching patients with severe hemophilia to rVIII-SingleChain or rIX-FP

OBJECTIVE

Prophylaxis treatment is the current standard of care for patients with severe hemophilia. Factor concentrates with improved pharmacokinetics have offered more options for individualizing treatment. The treatment focus may be on increased protection, aiming for higher trough factor levels or longer dosing intervals to reduce the burden of hemophilia. Both aspects can have long-term effects on joint health. Products, such as rVIII‑SingleChain and rIX-FP have been developed to reduce the treatment burden for patients with hemophilia and optimize prophylactic efficacy. The objective of this report is to provide a summary of the clinical experience of different Hemophilia Treatment Centers in managing the switch to rVIII-SingleChain or rIX-FP in patients with hemophilia.

METHODS

This report summarizes a selection of patient cases presented at the 3rd Alliance for Coagulation Academy Meeting in October 2020. The cases from the participating centers provide examples of the clinical experience in managing patients' switch to rVIII-SingleChain and rIX‑FP, including which types of patients are suitable for switching, and practical steps in managing a switch.

RESULTS

It is important to take into consideration the physical and social fulfillment of the patient when deciding to switch to rVIII-SingleChain or rIX-FP. The physician plays an important role in the motivation of patients as they understand not only the patient's needs but the potential benefits of the new treatment.

CONCLUSION

The selected patient cases reported here demonstrate that patients may wish to switch factor products for a variety of reasons; therefore, it is critical to understand why patients switch and what they expect from switching.

Determinants of adherence and consequences of the transition from adolescence to adulthood among young people with severe haemophilia (TRANSHEMO): study protocol for a multicentric French national observational cross-sectional study

INTRODUCTION

Severe haemophilia is a rare disease characterised by spontaneous bleeding from early childhood, which may lead to various complications, especially in joints. It is nowadays possible to avoid these complications thanks to substitutive therapies for which the issue of adherence is major. The transition from adolescence to adulthood in young people with severe haemophilia is a critical period as it is associated with a high risk of lack of adherence to healthcare, which might have serious consequences on daily activities and on quality of life.

METHODS AND ANALYSIS

We present the protocol for a cross-sectional, observational, multicentric study to assess the differences between adolescents and young adults with severe haemophilia in France through the transition process, especially on adherence to healthcare. This study is based on a mixed methods design, with two complementary and consecutive phases, comparing data from a group of adolescents (aged 14-17 years) with those from a group of young adults (aged 20-29 years). The quantitative phase focuses on the determinants (medical, organisational, sociodemographic and social and psychosocial and behavioural factors) of adherence to healthcare (considered as a marker of the success of transition). The qualitative phase explores participants' views in more depth to explain and refine the results from the quantitative phase. Eligible patients are contacted by the various Haemophilia Treatment Centres participating in the French national registry FranceCoag.

ETHICS AND DISSEMINATION

The study was approved by the French Ethics Committee and by the French National Agency for Medicines and Health Products Safety (number: 2016-A01034-47). Study findings will be disseminated to the scientific and medical community in peer-reviewed journals and presented at scientific meetings. Results will be popularised to be communicated via the French association for people with haemophilia to participants and to the general public.

TRIAL REGISTRATION NUMBER

NCT02866526; Pre-results.

Effect of target-enriched multiplex polymerase chain reaction on patient outcomes and costs during the 2013-14 influenza season

The US Centers for Disease Control and Prevention recommends the initial use of rapid antigen influenza diagnostic test (RIDT) for the detection of influenza A (H1N1-09). Nasopharyngeal samples were tested from 246 patients for H1N1-09 using target-enriched multiplex polymerase chain reaction (TEM-PCR), of which 163 were additionally tested via RIDT. RIDTs had a sensitivity of 18.7% compared with TEM-PCR as the reference standard. Patients with false-negative RIDTs were withheld from 111 days of oseltamivir and 65 days of isolation. Patients negative for H1N1 via TEM-PCR had antiviral therapy immediately stopped, thereby evading 408 days of oseltamivir and 315 days of unnecessary isolation. This cost avoidance saved US$208,982.

Retrospective comparative analysis of cardiovascular implantable electronic device infections with and without the use of antibacterial envelopes

BACKGROUND

Cardiovascular implantable electronic device (CIED) infections are associated with morbidity and mortality. Peri-operative systemic intravenous antibiotic prophylaxis reduces the rate of CIED infections. AIGIS_Rx, a polymer envelope implanted with the CIED, releases minocycline and rifampin, and has been introduced to reduce infections.

METHODS

Retrospective review of 184 patients who underwent CIED implantation was conducted. Ninety-two patients were implanted with an AIGIS_Rx envelope (AIGIS_Rx group) and 92 patients were not implanted with an AIGIS_Rx envelope (control group). Data were collected on demographics and risk factors for CIED infections (i.e. congestive heart failure, renal insufficiency, chronic kidney disease, oral anticoagulant use, chronic steroid use, need for lead replacement or revision, temporary pacing, early re-intervention, and having more than two leads in place). Rates of implantation success, major infections and mortality were compared between the AIGIS_Rx group and the control group.

RESULTS

The AIGIS_Rx group had longer hospitalizations (6.8±10.7 days vs 3.1±5.2 days; P=0.001), higher chronic corticosteroid use, higher rates of replacement or revision (51.1% vs 8.7%; P=0.001), and a greater proportion of devices with more than two intracardiac leads (42.4% vs 29.3%; P=0.03) than the control group. Successful implantation occurred in 97% of patients in both groups. Major infection was seen in 5.4% of cases in the AIGIS_Rx group and 1.1% of cases in the control group (P=0.048). Device removal was conducted in 3.3% of cases in the AIGIS_Rx group compared with 1.1% of cases in the control group (P=0.16). There were two deaths in the AIGIS_Rx group. Organisms cultured were meticillin-resistant Staphylococcus aureus, meticillin-susceptible S. aureus and Enterococcus faecalis.

CONCLUSION

The AIGIS_Rx group had higher rates of major infection but also higher risk factors compared with the control group. The rate of device extraction and CIED-related mortality was higher in the AIGIS_Rx group than in the control group.

Prenatal exposure to antibiotics, cesarean section and risk of childhood obesity

BACKGROUND/OBJECTIVES

Cesarean section (CS) and antibiotic use during pregnancy may alter normal maternal-offspring microbiota exchange, thereby contributing to aberrant microbial colonization of the infant gut and increased susceptibility to obesity later in life. We hypothesized that (i) maternal use of antibiotics in the second or third trimester of pregnancy and (ii) CS are independently associated with higher risk of childhood obesity in the offspring.

SUBJECTS/METHODS

Of the 727 mothers enrolled in the Northern Manhattan Mothers and Children Study, we analyzed the 436 mother-child dyads followed until 7 years of age with complete data. We ascertained prenatal antibiotic use by a questionnaire administered late in the third trimester, and delivery mode by medical record. We derived age- and sex-specific body mass index (BMI) z-scores using the CDC SAS Macro, and defined obesity as BMI z⩾95th percentile. We used binary regression with robust variance and linear regression models adjusted for maternal age, ethnicity, pre-gravid BMI, maternal receipt of public assistance, birth weight, sex, breastfeeding in the first year and gestational antibiotics or delivery mode.

RESULTS

Compared with children not exposed to antibiotics during the second or third trimester, those exposed had 84% (33-154%) higher risk of obesity, after multivariable adjustment. Second or third trimester antibiotic exposure was also positively associated with BMI z-scores, waist circumference and % body fat (all P<0.05). Independent of prenatal antibiotic usage, CS was associated with 46% (8-98%) higher offspring risk of childhood obesity. Associations were similar for elective and non-elective CS.

CONCLUSIONS

In our cohort, CS and exposure to antibiotics in the second or third trimester were associated with higher offspring risk of childhood obesity. Future studies that address the limitations of our study are warranted to determine if prenatal antibiotic use is associated with offspring obesity. Research is also needed to determine if alterations in neonatal gut microbiota underlie the observed associations.

A prospective registry of European haemophilia B patients receiving nonacog alfa, recombinant human factor IX, for usual use

Nonacog alfa, a recombinant factor IX (FIX) used for the treatment of haemophilia B, was approved in Europe in 1998. In accordance with European Medicines Agency requirements, a registry study was conducted from 2002 to 2009. A reformulated iso-osmotic version was approved for European use in 2007. This study was conducted to evaluate the safety of nonacog alfa in a usual care setting, and provide clinical trial and postmarketing surveillance data support. This open-label, non-interventional, prospective observational cohort study (registry) comprised 52 sites in nine European countries. Patients with haemophilia B receiving nonacog alfa in either formulation for prevention or treatment were followed on a usual care schedule. A total of 218 patients were enrolled, of whom 66 (30.3%) were <18 years of age. Haemophilia severity was evenly distributed, with baseline FIX activity of <1%, 1-5% and >5% in 33.3%, 36.6% and 30.1% of patients, respectively. One hundred thirty-eight patients received the original formulation alone; 80 switched to or received only the new formulation. There was a low incidence of events of special interest (ESIs), with less-than-expected therapeutic effect in five patients (2.2%), inhibitor development in two (0.9%), thrombosis in one (0.5%) and allergic events in eight (3.7%). These accounted for the majority of the 15 serious AEs reported in six patients. Six patients discontinued because of AEs, primarily related to hypersensitivity. Nonacog alfa was shown to be safe for the treatment of haemophilia B, with a low incidence of serious AEs and ESIs.

Prevalence of painful diabetic peripheral neuropathy among patients with diabetes mellitus in the Middle East region

The prevalence of painful diabetic peripheral neuropathy (DPN) was evaluated in type 1 or type 2 diabetes mellitus patients (n = 4097) attending outpatient clinics across the Middle East. Overall, 53.7% of 3989 patients with DN4 data met the criteria for painful DPN (Douleur Neuropathique-4 [DN4] scores ≥ 4). Significant predictors of painful DPN included long history (≥ 10 years) of diabetes (odds ratio [OR] 2.43), age ≥ 65 years (OR 2.13), age 50 - 64 years (OR 1.75), presence of type 1 versus type 2 diabetes (OR 1.59), body mass index > 30 kg/m(2) (OR 1.35) and female gender (OR 1.27). Living in one of the Gulf States was associated with the lowest odds of having painful DPN (OR 0.44). The odds of painful DPN were highest among patients with peripheral vascular disease (OR 4.98), diabetic retinopathy (OR 3.90) and diabetic nephropathy (OR 3.23). Because of the high prevalence and associated suffering, disability and economic burden of painful DPN, it is important that diabetic patients are periodically screened, using a simple instrument such as the DN4, and receive appropriate treatment if symptoms develop.

Screening markers of impaired glucose tolerance in the obese pediatric population

BACKGROUND

With the epidemic of childhood obesity, it is crucial to devise a simple screening protocol to predict impaired glucose tolerance (IGT) or pre-diabetes. The oral glucose tolerance test (OGTT), which is the gold standard for the diagnosis of IGT, is impractical for screening purposes. This pilot study was designed to formulate a simple, sensitive algorithm to predict IGT using clinical and laboratory parameters.

METHODS

Ethnicity, family history of diabetes, pubertal status, BMI z-score, blood pressure, lipids, hemoglobin A1c (HbA1c) and OGTT data were retrospectively collected from 209 overweight multi-ethnic subjects aged 3-21 years. Multivariate logistic regression was used to determine independent predictors of IGT.

RESULTS

HbA1c was the only significant predictor of IGT (p = 0.001), whereas fasting glucose was not. A cut-off of 5.5% had the best combined sensitivity (85.7%) and specificity (56.9%) with an odds ratio of 7.9 of having IGT when HbA1c is > or =5.5%. The remaining clinical parameters were not significant predictors of IGT.

CONCLUSION

While fasting blood glucose does not seem to be a predictor of IGT, we propose that HbA1c > or =5.5% can be used as a screening test to assess the risk of IGT and to determine who should undergo diagnostic OGTT. Large prospective studies validating our findings are warranted.

Factor VIII recovery after a single infusion of recalibrated ReFacto�in 14 severe haemophilia A patients

A recent multicentre collaborative study showed higher estimates of ReFacto potency when assayed with ReFacto Laboratory Standard(TM) (RLS) in comparison when standards consisting of full-length factor VIII (FVIII) were used. The RLS was hence recalibrated, leading to a 20% increase in the amount of ReFacto per vial without change in the labelled potency. The primary objective of this study was to determine the incremental and in vivo recovery of the recalibrated ReFacto in patients with severe haemophilia A. Fourteen male severe haemophilia A patients (FVIII < 1 IU dL(-1)) with a cumulative previous exposure days to any FVIII product >150 were administered an intravenous infusion 50 +/- 5 IU kg(-1) of ReFacto over a 5-min period. Blood samples were collected before infusion and after 15, 30 and 60 min. FVIII clotting activity (FVIII:C) was assessed in a central laboratory by the chromogenic substrate assay. After ReFacto infusion, peak FVIII:C was obtained within 15 min for 10 patients and within 30 min for the remaining four. Mean FVIII:C at peak was 117.7 +/- 17.3 IU dL(-1). Mean incremental recovery was 2.22 +/- 0.27 IU dL(-1) per IU kg(-1) while mean in vivo recovery was 105.9 +/- 14.6%. One patient reported three mild adverse events rated as 'unrelated' to the study drug. FVIII recovery after recalibrated ReFacto infusion falls within the expected range and is similar to the values reported for other FVIII concentrates.

Bile analysis of drugs in postmortem cases

Bile is, in certain cases, collected together with blood from different sites (heart, brain, femoral), urine and other organs or matrices. This study reports comparative results obtained from the analysis of blood and bile for different drugs found: acetaminophen, amphetamine and related compounds, several antidepressants, several benzodiazepines, cocaine and its metabolites, dextropropoxyphene and its metabolite, hydroxyzine, methadone and metabolite, morphine and codeine, levomepromazine, thioridazine, propranolol, tramadol and its metabolite. Several findings are presented: (1) There were no significant differences in the levels of the compounds among the samples of blood obtained from different sites. (2) Levels in bile are generally several fold higher than those in blood. The mean bile to blood ratios vary from about 1 (for acetaminophen, amphetamine) to about 2000 (for desmethylclobazam). (3) In certain cases (16 over 44), although the drug or its metabolite was not detected in blood from different sites, it was detected in bile. As other authors had advocated, it is very useful to ask the pathologist to take the gall bladder with its contents together with the other samples, in order that the sample of bile can be used in the comprehensive toxicological analysis and therefore be complementary to the other fluids or matrices. An additional advantage for using bile is that the concentrations of drugs or their metabolites are generally several fold higher than their blood concentrations.

Highly heterogeneous nature of delta-aminolevulinate dehydratase (ALAD) deficiencies in ALAD porphyria

The properties of 9 delta-aminolevulinate dehydratase (ALAD) mutants from patients with ALAD porphyria (ADP) were examined by bacterial expression of their complementary DNAs and by enzymologic and immunologic assays. ALADs were expressed as glutathione-S-transferase (GST) fusion proteins in Escherichia coli and purified by glutathione-affinity column chromatography. The GST-ALAD fusion proteins were recognized by anti-ALAD antibodies and were enzymatically active as ALAD. The enzymatic activities of 3 ALAD mutants, K59N, A274T, and V153M, were 69.9%, 19.3%, and 41.0% of that of the wild-type ALAD, respectively, whereas 6 mutants, G133R, K59N/G133R, F12L, R240W, V275M, and delTC, showed little activity (< 8%). These variations generally reflect the phenotype of ALAD in vivo in patients with ADP and indicate that GST-ALAD fusion protein is indeed useful for predicting of the phenotype of ALAD mutants. The location of F12L mutation in the enzyme's molecular structure indicates that its disturbance of the quaternary contact of the ALAD dimer appears to have a significant influence on the enzymatic activity. Mouse monoclonal antibodies to human ALAD were developed that specifically recognized a carboxy terminal portion of ALAD, or other regions in the enzyme. This study represents the first complete analysis of 9 mutants of ALAD identified in ADP and indicates the highly heterogeneous nature of mutations in this disorder.

Molecular analysis of delta-aminolevulinate dehydratase deficiency in a patient with an unusual late-onset porphyria

Cloning, expression, and genotype studies of the defective gene for delta-aminolevulinate dehydratase (ALAD) in a patient with an unusual late onset of ALAD deficiency porphyria (ADP) were carried out. This patient was unique in that he developed the inherited disease, together with polycythemia, at the age of 63. ALAD activity in erythrocytes of the patient was less than 1% of the normal control level. ALAD complementary DNA (cDNA) isolated from the patient's Epstein-Barr virus (EBV)-transformed lymphoblastoid cells had 2 base transitions in the same allele, G(177) to C and G(397) to A, resulting in amino acid substitutions K59N and G133R, respectively. It has been verified that the patient had no other ALAD mutations in this and in the other allele. By restriction fragment length polymorphism (RFLP) analysis, all family members of the proband who had one-half ALAD activity compared with the ALAD activity of the healthy control were shown to have the same set of base transitions. Expression of ALAD cDNA in CHO cells revealed that K59N cDNA produced a protein with normal ALAD activity, while G133R and K59N/G133R cDNA produced proteins with 8% and 16% ALAD activity, respectively, compared with that expressed by the wild type cDNA. These findings indicate that while the proband was heterozygous for ALAD deficiency, the G(397) to A transition resulting in the G133R substitution is responsible for ADP, and the clinical porphyria developed presumably due to an expansion of the polycythemic clone in erythrocytes that carried the mutant alad allele.

Immunologic factors: the major risk for decreased long-term renal allograft survival

BACKGROUND

Both antigen-dependent (immunologic) and non-antigen-dependent (nonimmunologic) factors have been implicated in long-term renal allograft loss. Differentiating between these two factors is important because prevention strategies differ.

METHODS

To isolate the importance of these 2 factors, we studied long-term actuarial graft survival in a cohort of adult kidney recipients who underwent transplants at a single institution between January 1, 1984 and October 31, 1998. Excluded were recipients with graft loss as a result of death with function, technical failure, primary nonfunction, and recurrent disease, leaving 1587 recipients (757 cadaver [CAD], 830 living donor [LD]) who would be at risk for graft loss secondary to both immunologic and nonimmunologic factors. These recipients were analyzed in the following 2 groups: those treated for a previous episode of acute rejection (AR) (Group1; n = 588; 328 CAD, 260 LD) and those with no AR (Group 2: n = 999; 429 CAD, 570 LD). Actuarial graft survival and causes of graft loss were determined for each group. Presumably, graft loss in Group 1 would be caused by immunologic and nonimmunologic factors; graft loss in Group 2 would be caused primarily by nonimmunologic factors.

RESULTS

The 10-year graft survival rate (censored for death with function, technical failure, primary nonfunction, and recurrent disease) in Group 2 was 91%. In contrast, the 10-year graft survival rate in Group 1 was 45% (P<0.001 vs. Group 2). Causes of graft loss in Group 2 were chronic rejection in 1.8% (3.0% CAD, 0.9% LD), de novo disease, 0.4%; sepsis, 0.2%; discontinuation of immunosuppressive therapy, 0.3%; and unknown, 0.6%. In contrast, 23.8% (29.9% CAD, 16.2% LD) of recipients in Group 1 had graft loss caused by chronic rejection (P = 0.001 vs. Group 2).

CONCLUSIONS

This very low incidence of chronic rejection in recipients without previous AR suggests that immunologic factors are the main determinants of long-term kidney transplant outcome; nonimmunologic factors in isolation may have only a minimal impact on long-term graft survival.

Simultaneous detection and quantification of acidic and basic drugs in serum toxicological screening: use of ion-pairing technique in liquid-liquid extraction

The toxicological screening, using the combination of high performance liquid chromatography with diode array ultraviolet detector and ion-pairing technique in liquid-liquid extraction, is an effective tool in the identification and quantification of the acidic and basic substances in a single run. The use of an ion-pairing technique in the conventional extraction shows the co-extraction of the uncharged and charged form of the analytes present in a serum sample. The stationary phase used is C-18-bonded phase. The mobile phase is acetonitrile--phosphate buffer (pH 3; 25 mM) containing 25 mM triethylammonium as ion-pairing agent. The analytical validation shows reproducible recoveries, good day-to-day repeatability and sensible results compatible with clinical and forensic use.

Ethanol treatment of tendon allografts: a potential HIV inactivating procedure

The penetration rate of ethanol in human tendons was studied to in order to define the conditions which were necessary to achieve an inactivating concentration against the Human Immunodeficiency Virus (HIV) within the tendon. The rate of alcohol penetration was found to be slow and did not differ with different types of tendons. An average ethanol concentration of 14% (v/v) was measured in human tendons after they had been immersed for 2 h in 70% (v/v) ethanol, and a concentration of 19% (v/v) was reached after 3 h. Ethanol immersion of human tendons may represent an additional safety procedure in inactivating the HIV virus provided the duration is at least 3 h.

Ethylene glycol poisoning treated by intravenous 4-methylpyrazole

A 19-year-old woman was admitted 45 min after ethylene glycol (EG) ingestion. The initial serum EG concentration was 1.34 g/l (21.6 mmol/l), the anion gap 14.5, and the osmolal gap 24. Renal function was preserved (serum creatinine 75.1 micromol/l). As the patient was seen soon after poisoning, before the development of metabolic acidosis, therapy with 4-methylpyrazole (4-MP) was proposed as an antidote. 4-MP was administered via the intravenous route (7 mg/kg as loading dose, followed by 3.6, 1.2, 0.6, and 0.6 mg/kg at intervals of 12 h). 4-MP alone was effective in preventing EG biotransformation to toxic metabolites (absence of metabolic acidosis and renal injury). Ethanol therapy, hemodialysis, and sodium bicarbonate administration were not required. The half-life of EG during 4-MP therapy was 11 h, with a mean EG renal clearance of 26.9 ml/min, and a total of 65.3 g EG was eliminated unchanged in the urine. 4-MP therapy was also well tolerated.

Excretion of tacrolimus glucuronides in human bile

Tacrolimus is extensively metabolized by the cytochrome P-450 system. Hepatic metabolic phase I reactions of tacrolimus include mainly demethylation and/or hydroxylation. No valid data have been published on phase II pathways (glucuronide- or sulfo-conjugation). In order to investigate these pathways, different beta-glucuronidase/sulfatase enzyme preparations were used to hydrolyse the conjugates potentially present in human bile extracts. Two analytical methods were used: a non-specific method, MEIA, and a specific combined HPLC/MEIA method. The influence of the extraction pH was investigated. After beta-glucuronidase hydrolysis and extraction at pH 5, tacrolimus concentrations, obtained either from HPLC-MEIA or MEIA, always appeared significantly higher, suggesting the presence of glucuronides in the bile. When the extraction was performed at pH 1.5, only the HPLC-MEIA concentrations appeared higher after hydrolysis. MEIA concentrations obtained before and after hydrolysis were similar. These data are consistent with the fact that glucuronides are extracted at pH 1.5 but not at pH 5 and suggest first that, without hydrolysis, the extracted glucuronides are separated from the tacrolimus fraction in the HPLC-MEIA procedure, and second, that the glucuronides are cross-detected by the monoclonal antibody in the immunoassay. From these data, it is concluded that clues have been found, suggesting the presence in human bile of tacrolimus glucuronides, which cross-react with the monoclonal antibody, provided they are extracted in the sample tested.

HPLC-microparticle enzyme immunoassay specific for tacrolimus in whole blood of hepatic and renal transplant patients

Tacrolimus is a relatively new immunosuppressant used in organ transplantation to prevent graft rejection. However, its use is not devoid of side effects, making it important to maintain blood concentrations within therapeutic ranges. Several analytical methods are currently available for routine drug monitoring. However, these methods are based on use of the same monoclonal antibody, which also cross-reacts with some metabolites, resulting in overestimation of some blood concentrations. Even though this antibody appears appropriate for therapeutic drug monitoring, no reference method measures only the parent drug, mainly because of the poor absorptivity of tacrolimus in ultraviolet light. We have developed a method displaying an increased specificity towards the unchanged drug, using conventional equipment available in most clinical laboratories. After chromatographic separation of the blood extract, the tacrolimus fraction is analyzed by an automated microparticle enzyme immunoassay (MEIA) performed on the IMx analyzer (Abbott Labs.). This method is linear from 0 to 40 micrograms/L, yields CVs from 8.5% to 18.2%, and has a detection limit of 5 micrograms/L. Tacrolimus concentrations obtained by HPLC-MEIA in hepatic and renal transplant patients are from 47.5% to 18.8% lower than those obtained by MEIA, according to liver function tests and metabolite accumulation, even though no significant differences were observed between the methods for drug-free blood samples supplemented with known amounts of tacrolimus.

HPLC-microparticle enzyme immunoassay specific for tacrolimus in whole blood of hepatic and renal transplant patients

Tacrolimus is a relatively new immunosuppressant used in organ transplantation to prevent graft rejection. However, its use is not devoid of side effects, making it important to maintain blood concentrations within therapeutic ranges. Several analytical methods are currently available for routine drug monitoring. However, these methods are based on use of the same monoclonal antibody, which also cross-reacts with some metabolites, resulting in overestimation of some blood concentrations. Even though this antibody appears appropriate for therapeutic drug monitoring, no reference method measures only the parent drug, mainly because of the poor absorptivity of tacrolimus in ultraviolet light. We have developed a method displaying an increased specificity towards the unchanged drug, using conventional equipment available in most clinical laboratories. After chromatographic separation of the blood extract, the tacrolimus fraction is analyzed by an automated microparticle enzyme immunoassay (MEIA) performed on the IMx analyzer (Abbott Labs.). This method is linear from 0 to 40 micrograms/L, yields CVs from 8.5% to 18.2%, and has a detection limit of 5 micrograms/L. Tacrolimus concentrations obtained by HPLC-MEIA in hepatic and renal transplant patients are from 47.5% to 18.8% lower than those obtained by MEIA, according to liver function tests and metabolite accumulation, even though no significant differences were observed between the methods for drug-free blood samples supplemented with known amounts of tacrolimus.

Accumulation of protoporphyrin isomers I and III, and multiple decarboxylation products of uroporphyrin in a case of porphyria in a slaughtered pig

Pathological and biochemical examinations were made on tissues from a case of porphyria in a slaughtered pig. Bones, kidneys, teeth and lymph nodes showed a mahogany discoloration. Histologically, the pigment was negative on staining for iron (Gomori) and showed a strong red-orange fluorescence under UV light proving it to be porphyrin. Biochemical studies on the kidney, lymph nodes, bone and bone marrow revealed a 'mixed' erythropoietic protoporphyria-coproporphyria. This indicates that the case presented probably represented both a uroporphyrinogen decarboxylase and uroporphyrinogen-III-cosynthase dysfunction.

Adverse cardiac manifestations following dextropropoxyphene overdose: can naloxone be helpful?

Dextropropoxyphene overdose may be complicated by serious cardiovascular manifestations, including conduction abnormalities and collapse. We report two patients in whom cardiac toxicity developed. Cardiovascular depression seemed to be improved after naloxone infusion in these two cases. Possible mechanisms are briefly discussed.

Outcome following organ removal from poisoned donors in brain death status: a report of 12 cases and review of the literature

Experience with organ procurement from poisoned donors in brain death status is still limited in comparison with other etiologies. From 1963 to 1993, 2769 grafts (heart 141, kidney 1922, liver 623, pancreas 43) were performed in our University Hospital. Since 1975, among 1174 patients admitted to the ICU for acute poisoning, 12 patients who developed brain death status were considered for organ donation. The toxics involved were: methaqualone (1), benzodiazepines (1), benzodiazepines plus tricyclic antidepressants (2), barbiturates (2), insulin (2), carbon monoxide (1), cyanide (1), methanol (1), and acetaminophen (1). Exclusion criteria for organ removal were applied according to the nature of the toxin and the general criteria used for organ donation. The organs removed were: heart 5, heart valves for graft bank 2, kidneys 22, liver 4, pancreas 2, pancrease islet cells 2. Pertinent follow-up was obtained in 23 of 32 recipients. Immediate outcome was favorable in 20/23 patients (85%). Three patients died either from stroke, heart failure or preexisting encephalopathy. Two patients died from either chronic hepatic or renal graft rejection. None of these events could be directly related to a toxic origin. The one year survival rate of 75% is similar to that observed in the population who received organs from nonpoisoned donors. Organ procurement can be considered in few selected cases of acute poisoning. The accuracy of the diagnosis of irreversible brain damage is essential in this setting.

Inhibitory effects of solvent and solid-phase extraction residues on mixed lymphocyte cultures

Residues from eight solvents/solvent mixtures before and after their passage through C18- bonded phase columns were assayed for cytostatic activity using mixed lymphocyte cultures (MLC). All residues, except those from acetonitrile, exhibited cytostatic activity (15%-35% MLC inhibition as measured by 3H-thymidine incorporation). Passage of solvents through bonded phase columns contributed an additional and significant cytostatic effect (19%-69% MLC inhibition). Pretreatment of columns with methanol led to further increases in the release of cytostatic residues from the columns, only when followed by less polar solvents (hexane, ethylacetate, etc.). It is concluded that residues from solid-phase extraction columns may interfere with subsequent cell culture-based assays for proliferative/antiproliferative activity.

Unusual manifestations after malathion poisoning

We report a case of organophosphate poisoning with a commercial preparation of malathion (deliberate ingestion of Malathane Garden Spray: malathion 15% in isopropyl alcohol) in which the initial cholinergic crisis was followed by cardiac, pulmonary, neurological and renal manifestations. They occurred when erythrocyte and plasma cholinesterases were reactivating. A chemical analysis of the pesticide preparation revealed, apart from malathion itself, the presence of isopropylmalathion and O,O,S-trimethylphosphorothioate. Although pure malathion is regarded as one of the safest organophosphate insecticides, this observation underlines the possibility of severe complications after exposure to a preparation which has been stored for a long period of time.

Potential use of a radioreceptor assay for the determination of benzodiazepine compounds in serum

The clinical monitoring and intensive care of patients who have taken an overdose of a benzodiazepine require rapid and quantitative methods to assess benzodiazepine concentrations in biological fluids. A radioreceptor assay (RRA) permits the simultaneous measurement of the benzodiazepine molecules that bind to the receptor, providing a total estimate of all pharmacologically active forms of the drug(s) (parent drug and active metabolites). This study describes the development of an RRA for the determination of benzodiazepine compounds in serum using a lyophilized bovine brain cerebral cortex receptor preparation. The standard curves and the sensitivity of this RRA are determined for 20 different benzodiazepines and the specific antagonist flumazenil. The sensitivity ranges from 5 ng/mL for clonazepam to 3500 ng/mL for chlordiazepoxide. The IC50 values are significantly correlated (r = 0.81) with the lowest recommended therapeutic concentrations. The advantages and disadvantages of this RRA are discussed and compared with those of other chromatographic and immunological methods.

Improvement and assessment of enzyme-linked immunosorbent assay to detect low FK506 concentrations in plasma or whole blood within 6 hours

FK506, a promising new immunosuppressant, is currently under clinical investigation. Because dose-dependent toxicity is possible, blood concentrations of FK506 should be monitored. We improved the original ELISA of FK506 by shortening the incubation time. With some modification of materials, results are obtained within 6 h instead of 2 days, with similar or even better precision. Internal and external quality-control programs showed that our results correlated satisfactorily both with values determined by the original method and the theoretical expected values. Either plasma (detection limit 0.1 microgram/L) or whole-blood (detection limit 1 microgram/L) samples can be used. The sensitivity of the method makes it particularly useful for accurate pharmacokinetic studies or measurement of low blood concentrations. Twenty-four drugs and nine biological variables showed no significant interference on the assay. Study of the concentration- and temperature-dependent distribution of FK506 shows that the drug is largely bound to erythrocytes (ratio of blood to plasma concentrations is 10-40); as the erythrocytes become saturated, more of the drug is found in the plasma. Plasma concentrations may vary according to the blood temperature. We conclude that whole blood should be used for FK506 monitoring, as it is for monitoring cyclosporine.

Improvement and assessment of enzyme-linked immunosorbent assay to detect low FK506 concentrations in plasma or whole blood within 6 hours

FK506, a promising new immunosuppressant, is currently under clinical investigation. Because dose-dependent toxicity is possible, blood concentrations of FK506 should be monitored. We improved the original ELISA of FK506 by shortening the incubation time. With some modification of materials, results are obtained within 6 h instead of 2 days, with similar or even better precision. Internal and external quality-control programs showed that our results correlated satisfactorily both with values determined by the original method and the theoretical expected values. Either plasma (detection limit 0.1 microgram/L) or whole-blood (detection limit 1 microgram/L) samples can be used. The sensitivity of the method makes it particularly useful for accurate pharmacokinetic studies or measurement of low blood concentrations. Twenty-four drugs and nine biological variables showed no significant interference on the assay. Study of the concentration- and temperature-dependent distribution of FK506 shows that the drug is largely bound to erythrocytes (ratio of blood to plasma concentrations is 10-40); as the erythrocytes become saturated, more of the drug is found in the plasma. Plasma concentrations may vary according to the blood temperature. We conclude that whole blood should be used for FK506 monitoring, as it is for monitoring cyclosporine.

[Drug-induced syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Review of literature]

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is caused by an incapacity of plasmatic hypotonia to inhibit antidiuretic hormone (ADH) secretion. This phenomenon leads to a water retention and an expanded extracellular fluid volume, and secondary to a dilution of plasmatic sodium and also to a renal loss of sodium. The SIADH is a relatively rare syndrome, which may occur in various circumstances: central nervous system diseases, cancers, infections... Sometimes, it may be observed as a drug-related side effect: carbamazepine, chlorpropamide, antidepressors, anticancer drugs are particularly involved.

Use of octreotide in the treatment of digestive neuroendocrine tumours. Seven year experience in 20 cases including 9 cases of metastatic midgut carcinoid and 5 cases of metastatic gastrinoma

The authors report their experience with octreotide in 20 patients (median age 57 years, 10 M, 10 F) from 1984 to 1991; 16 had metastatic APUDoma: 1 PPoma with VIPoma, 1 glucagonoma, 5 gastrinoma including 1 associated to PP-oma, 9 mid-gut carcinoid; 3 patients had multiple-endocrine neoplasia type I (MEN-I) with Zollinger-Ellison syndrome (ZES) and 1 patient a non-metastatic VIPoma. Octreotide (200-750 micrograms/day) was administered bid or tid with regular laboratory controls and morphological assessment. There was a striking improvement of symptoms, particularly in the carcinoid group (reduction of flushing in all patients and of diarrhoea in 3/5), in the patient with gastrinoma + acromegaly (regression of congestive heart failure) and in the patient with non-metastatic VIPoma. The hormonal markers were markedly reduced, particularly gastrin, PP (except in the patient with PPoma + VIPoma), VIP, GH and Somatomedin-C and urinary 5HIAA in 4/9 patients with carcinoid. There was only one partial regression of metastases (gastrinoma) and 4 apparent stabilizations of tumour growth, in the 16 metastatic cases. Among them, 4 patients died: 1 glucagonoma, 1 PPoma + VIPoma, 2 mid-gut carcinoids after a treatment of 5, 16, 30, 36 months, respectively. The patient with acromegaly + ZES died after 6 years of treatment at age 81. A patient with prolactinoma, resected insulinoma, hyperparathyroidism and ZES was not improved by a short course of octreotide (hypoglycemia); he died later of recurrent insulinoma. In conclusion, octreotide is a useful drug to control most of the symptoms related to gut endocrine tumours; it may inhibit tumour growth.

The Use of Radioreceptor Assays for the Determination of Benzodiazepines in Biological Samples: A Review

Benzodiazepines are the most widely prescribed class of psychotropes. The demonstration of specific, high affinity binding sites for benzodiazepines in mammalian brain has provided a basis for a radioreceptor assay (RRA) of these compounds in biological samples (fluids or tissues). The RRA permits the simultaneous measurement of the benzodiazepine molecules that bind to the receptor, providing a total estimate of all pharmacologically active forms of the drug, which is useful in drug monitoring and in the intensive care of patients. After a complete description of the methodological aspects of this technique, the results obtained in therapeutic monitoring and in toxicological analysis are reviewed, and the advantages and disadvantages of this method are examined.

Repeated doses of activated charcoal and cholestyramine for digitoxin overdose: pharmacokinetic data and urinary elimination

A 48-year-old man chronically treated with digitoxin and verapamil for prevention of atrial fibrillation voluntarily ingested 2.2 mg of digitoxin. Serum digitoxin concentrations and the urinary elimination of the drug were followed over a 12-day period. Urinary data indicate that a large percentage (50%) of the drug was eliminated renally despite administration of multiple doses of activated charcoal, cholestyramine and hyperosmotic laxatives. The possible interaction with two other drugs, heparin and verapamil, is also discussed.

Amrinone for refractory cardiogenic shock following chloroquine poisoning

Cardiac arrhythmias and circulatory collapse account for the high mortality reported after severe chloroquine poisoning. We have recently observed a 17-year-old man who ingested an 8 g chloroquine overdose. Cardiac arrest occurred within 1 h. Cardiogenic shock was refractory to epinephrine, dopamine and molar sodium lactate. Amrinone, a bipyridine analog, was then successfully used to improve haemodynamic conditions.

Hereditary hepatic porphyria due to homozygous delta-aminolevulinic acid dehydratase deficiency: studies in lymphocytes and erythrocytes

Activities of delta-aminolevulinic acid (ALA) dehydratase and porphobilinogen (PBG) deaminase, and haem content were determined in EB-virus transformed lymphocytes from two patients with homozygous ALA dehydratase deficiency, and their family members to determine the expression of the specific gene defect in this cell type. ALA dehydratase activity, but not PBG deaminase activity or haem content, was markedly decreased in lymphocyte preparations from both patients with homozygous enzyme deficiency, and moderately decreased in subjects heterozygous for enzyme deficiency. Immunochemical quantitation of erythrocyte ALA dehydratase suggested the presence of a cross-reactive material in a patient with a late-onset of acute hepatic porphyria due to the homozygous enzyme deficiency.

[Association of idiopathic hemochromatosis and tardive cutaneous porphyria]

Porphyria cutanea tarda is a disorder of porphyrin metabolism that results from a deficiency of uroporphyrinogen decarboxylase, resulting in a characteristic pattern of porphyrin excretion. Elevated serum iron values are frequently observed among patients with porphyria cutanea tarda. The hypothesis has been advanced that a hemochromatosis allele is implicated in the clinical manifestation of porphyria cutanea tarda. We report the case of a patient suffering from both idiopathic hemochromatosis and porphyria cutanea tarda. The data of the medical literature concerning such an association are discussed.