Biomedical subjects
Publications and source records attributed to R E Dupuis.
Post-transplant complications are common among patients receiving immunosuppressive medications, including pain syndromes. Recently, a pain syndrome, calcineurin-inhibitor induced pain syndrome (CIPS) has been described. To our knowledge, this article is the second report of tacrolimus-associated CIPS, and the first report in the pediatric setting.
Simultaneous determination of mycophenolic acid (MPA) and mycophenolate phenol glucuronide (MPAG) in plasma and urine was accomplished by isocratic HPLC with UV detection. Plasma was simply deproteinated with acetonitrile and concentrated, whereas urine was diluted prior to analysis. Linearity was observed from 0.2 to 50 microg/ml for both MPA and MPAG in plasma and from 1 to 50 microg/ml of MPA and 5 to 2000 microg/ml MPAG in urine with extraction recovery from plasma greater than 70%. Detection limits using 0.25 ml plasma were 0.080 and 0.20 microg/ml for MPA and MPAG, respectively. The method is more rapid and simple than previous assays for MPA and MPAG in biological fluids from patients.
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The pharmacokinetics of tobramycin in patients with cystic fibrosis before and after lung transplantation were evaluated. Twenty-nine lung transplant recipients with cystic fibrosis who received at least one course of tobramycin pre- and posttransplantation were included in this study. Pharmacokinetic parameters (clearance, volume of distribution, elimination rate and half-life) were calculated using a one-compartment Bayesian method. Comparisons were made both between and within pre- and posttransplant periods for patients receiving multiple courses. Significant differences were noted. Clearance was decreased 40%, volume of distribution increased 20%, elimination rate increased 52%, and half-life increased 141%, respectively, posttransplant as compared to pretransplant. There were no differences within each time period between each tobramycin course. The results indicate that tobramycin pharmacokinetics are significantly altered in patients with cystic fibrosis after lung transplantation. Patients with cystic fibrosis require early and close monitoring of tobramycin after lung transplantation.
A study was conducted to determine whether assay-specific quantitative differences exist in the determination of vancomycin serum concentrations obtained from patients with renal dysfunction. Vancomycin serum concentrations were obtained during the first week of therapy for each of three time intervals: 48-96 h, 96-144 h, and 144-192 h after administration of the first dose of vancomycin. Vancomycin serum concentrations were measured using the enzyme-multiplied immunoassay technique (EMIT) and fluorescence polarization immunoassay (FPIA). Twenty patients with an estimated creatinine clearance < 40 ml/min who were receiving intravenous vancomycin were evaluated. Hemodialysis was required in 16 of 20 patients. Fifty samples were included in the data analysis. The mean (+/-SD) serum concentrations obtained with EMIT and FPIA were 10.9 mg/L (+/-5.3) and 12.6 mg/L (+/-5.7), respectively (p = 0.13), and were not statistically different. A linear relationship was observed between EMIT and FPIA (EMIT = 0.89 x FPIA - 0.24; r2 = 0.93). No statistically significant differences were observed in the calculated pharmacokinetic parameters between methods. FPIA and EMIT are comparable methods in determining vancomycin serum concentrations within the first week of vancomycin therapy in patients with moderate to severe renal dysfunction.
OBJECTIVE: To describe delayed peak lithium concentrations after an overdose of extended-release lithium tablets. CASE SUMMARY: A patient with borderline personality disorder and depression ingested extended-release lithium approximately 20.25 g along with other agents. At presentation, the lithium concentration was 1.4 mEq/L. Significant enteral intake was initiated 27 hours after presentation and the lithium concentration 5 hours later increased to 3.2 mEq/L. A second lithium peak concentration of 5.0 mEq/L was noted 40 hours after presentation. Two hemodialysis sessions lasting 4 hours each were performed along with administration of sodium polystyrene sulfonate in sorbitol 20% to enhance lithium elimination and decrease absorption. Eighty-eight hours after presentation, the lithium concentration had decreased to 1.5 mEq/L. DISCUSSION: Delayed and secondary peak lithium concentrations have been reported following an overdose with an extended-release product. Extended-release lithium may form an aggregate in the gastrointestinal tract and/or have delayed absorption secondary to coingested drugs. Toxicity may result if the patient begins enteral intake of drugs, fluids, or nutrition. CONCLUSIONS: Continued monitoring of lithium concentrations after an acute ingestion with an extended-release product are recommended until lithium concentrations are less than 1.5 mEq/L and there are no signs of toxicity, particularly once the patient begins significant enteral intake.
BACKGROUND: A study involving two groups of patients with cardiovascular disease was conducted to compare empiric (clinician-directed) heparin therapy with therapy based on a nomogram-determined dosage. The comparison was based on (1) the average weight-referenced infusion rate yielding a therapeutic activated partial thromboplastin time (APTT) and (2) the time required to reach a therapeutic APTT (55 to 95 seconds) after empiric or nomogram-based heparin therapy was initiated. METHODS: Data were collected for patients admitted to the cardiology service at a university health science center in two phases: phase 1 (April 1 through June 30, 1992), involving 95 patients receiving heparin therapy, with 88 patients included in the data analysis, and phase 2 (March 11 through June 11, 1993), involving 156 patients receiving heparin therapy, with 45 patients receiving nomogram-guided therapy included in the data analysis. RESULTS: In phase 1, 66 patients (75.0%) achieved a therapeutic APTT some time during their heparin therapy, with an average time to therapeutic APTT of 20.7 + 19.1 hours. Regression analysis demonstrated a statistically significant relationship between the heparin infusion rate at the time of the patient's first therapeutic APTT and the patient's total body weight (r2 = .3043). An initial infusion rate based on total body weight (13 U/kg per hour) was therefore used as the basis for the nomogram in phase 2. In phase 2, 41 patients (91.1%) achieved a therapeutic APTT at some time during their heparin therapy, with an average time to therapeutic APTT of 13.1 + 11.9 hours, statistically significantly shorter than that in phase 1. A greater proportion of patients in phase 2 compared with patients in phase 1 reached the therapeutic range within 12 hours (62.2% vs 34.1%) and within 24 hours (77.8% vs 54.5%). CONCLUSIONS: Use of a weight-based nomogram to determine the initial and maintenance heparin infusion rates was associated with a higher percentage of patients admitted to the cardiology service reaching the targeted therapeutic APTT range at a time earlier in the course of therapy compared with empiric dosing.
OBJECTIVE: To review the literature investigating increased lipid concentrations in transplant recipients and the use of lipid-lowering agents in this population. DATA SOURCES: Relevant articles were identified from a MEDLINE search using the terms transplantation, hyperlipidemia, immunosuppression, and therapy including diet, gemfibrozil, bile acid sequestrants, nicotinic acid, probucol, and hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Selected literature, including controlled studies, was used in this review. STUDY SELECTION: Articles published since 1970 pertaining to hyperlipidemia in solid organ transplant recipients. Emphasis was placed on clinical trials that investigated approaches to the treatment of hyperlipidemia in transplant recipients. DATA EXTRACTION: Original articles and reviews were obtained to select material pertinent to the objectives. DATA SYNTHESIS: Descriptions of lipid concentrations in the transplant patient and treatment approaches used, including potential complications, were reviewed. CONCLUSIONS: Hyperlipidemia is an important risk factor for coronary heart disease in the solid organ transplant patient. Treatment alternatives include diet modification and, in most cases, pharmacologic intervention that should be based on the type of hyperlipidemia. The HMG-CoA reductase inhibitors are effective agents in the treatment of hyperlipidemia in the transplant recipient and generally are used as single therapy in low dosages to minimize the risk of myositis or rhabdomyolysis.
To assess the reliability of salivary theophylline concentrations for patient monitoring, concentrations of theophylline in sera and saliva of 50 patients (ages 6-81 years) receiving oral or parenteral theophylline were determined by two methods: a rapid dry-phase apoenzyme reactivation system (ARIS) and fluorescence polarization immunoassay (FPIA). Saliva production was stimulated by both citric acid (CA) and parafilm (PF). With both analytical methods, there were excellent correlations between salivary theophylline concentration, CS, and unbound serum theophylline concentration CU (r2 > 0.95), and between CS and total serum theophylline concentration, CT (r2 > 0.85). CA- and PF-stimulated CS by FPIA resulted in concentrations within 2.0 micrograms/ml of the actual CU for 100% of the samples measured (n = 47). By ARIS, 100% of the PF-stimulated CS and 93.6% of the CA-stimulated CS determinations were within 2.0 micrograms/ml of the CU (n = 47). To evaluate the predictive capabilities of PF- and CA-stimulated saliva, one-half (n = 24) of the patients were randomly selected and their data used to predict the CT for the remaining patients. FPIA PF-CS predicted 83.3% (20/24) of CT within +/- 2 micrograms/ml, while ARIS CA-CS predicted 75.0% within +/- 2 micrograms/ml. There was no difference between FPIA CS and ARIS CS results by multivariate analysis of variance (MANOVA), but there was a difference between PF-CS and CA-CS (p < 0.05). However, when CU was used as a covariant, there was no significant difference. Using appropriate saliva collection procedures and the FPIA system, we conclude that CS provides adequate reliability for therapeutic drug monitoring of theophylline.
OBJECTIVE: Our purpose was to compare the pharmacokinetic parameters of oral administration of a 35 micrograms ethinyl estradiol, 1 mg norethindrone pill in peritoneal dialysis patients and normal women. STUDY DESIGN: A single-dose study was performed with five patients and four controls, followed by a multiple-dose study with five subjects in each group. Pharmacokinetic parameters were calculated by noncompartmental analysis and statistical analysis performed with Mann-Whitney U testing. RESULTS: There is no difference in the pharmacokinetic parameters for norethindrone in peritoneal dialysis patients compared with normal women. During multiple dosing an increased area under the concentration curve and decreased apparent oral clearance was observed for ethinyl estradiol in peritoneal dialysis patients compared with normal women. CONCLUSION: Peritoneal dialysis patients have decreased apparent oral clearance of ethinyl estradiol, leading to slightly higher serum concentrations compared with women with normal renal function. The clearance of norethindrone is the same in peritoneal dialysis patients and normal women.
Analysis of salivary digoxin using a rapid dry chemistry, enzyme-labeled immunometric assay (ELIA) was compared with fluorescence polarization immunoassay (FPIA). Saliva and serum samples were obtained from 40 hospitalized patients who were taking digoxin chronically and from 8 patients just prior to treatment with digoxin. Unstimulated saliva samples were collected from 20 patients; however, saliva volumes from 10 pediatric patients were inadequate to permit analysis by FPIA, and 1 other had unmeasurable concentrations by both methods. Stimulated saliva was collected by having patients chew a small piece of Parafilm for 1-2 min. Salivary digoxin was analyzed using the same procedure recommended for serum digoxin by each manufacturer. There were no significant differences found between ELIA and FPIA determinations of unstimulated or stimulated salivary digoxin, serum digoxin, or saliva/serum concentration ratios. The saliva/serum ratio of the unstimulated group was approximately twice that of the stimulated group (p less than 0.01) by both methods, suggesting that salivary digoxin concentration decreases with increased saliva production rate. Excellent correlations were found between ELIA and FPIA salivary digoxin concentrations and between stimulated saliva and serum concentrations by both assays. Weaker correlations were observed between unstimulated saliva and serum concentrations. There was no evidence of assay interference with either method in eight nondigitalized patients, each taking an average of 6.5 medications. The ELIA appears to provide equivalent results compared with the FPIA for the determination of salivary digoxin concentration. Further investigations are needed before salivary digoxin concentration monitoring can be recommended as an acceptable alternative to serum monitoring.
Critically ill patients often have or develop conditions that make them susceptible to seizures and epilepsy. Treatment frequently involves the use of anti-convulsants. In order to use these effectively, the critical care nurse must be aware of the indications and controversies surrounding their use, the patho-physiologic conditions that impact on the disposition, and appropriate dosing and monitoring of these agents in the critical care setting.
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Idiosyncratic hepatotoxicity, although rare, is of major concern when one is treating patients with valproate (VPA). Several clinical criteria are associated with an increased risk of developing this complication, but more specific predictors are needed. It has been postulated that 4-en-VPA or one of its further metabolites may be responsible for the hepatic toxicity and that under certain conditions the metabolism of VPA is shifted to this product. We postulated that measurement of serum concentrations of 4-en-VPA or another metabolite might be a simple technique that would be predictive of risk for developing idiosyncratic hepatotoxicity. Because this complication is rare, we chose to analyze our data by a multiple linear regression model, exploring associations between VPA or three of its metabolites and clinical risk factors for hepatotoxicity. 4-en-VPA correlated with older age and absence of encephalopathy. 4-en-VPA was only seen in patients receiving polytherapy; all patients were also receiving CBZ. 2-en-VPA correlated with poor nutritional status. We conclude that routine measurement of serum 4-en-VPA is unlikely to be a useful predictor of risk for developing fatal hepatotoxicity. Serum concentrations of 4-en-VPA may not reflect presence or effects in the liver as it may be metabolized to further intermediates or be bound to tissue. Thus, serum levels of 4-en-VPA do not reflect its important role in the pathogenesis of hepatotoxicity. This metabolite was detected only in patients receiving polytherapy, a potent risk factor for developing this rare complication.
Acute toxicity in the setting of valproic acid (valproate sodium) overdose is in most cases benign and readily reversible. However, serious toxicity has been reported. We present a case of accidental acute valproic acid overdose in a 26-month-old female, in whom serious neurological, metabolic, haematological and respiratory sequelae occurred. The major toxicity observed was delayed cerebral oedema. We also present data not previously reported, which describes the pharmacokinetic disposition of valproic acid and several of its metabolites during the course of this acute overdose. A comparison of an enzyme immunoassay and gas liquid chromatographic methodologies for measuring valproic acid in this setting is also presented. It appears that the 2-EN-valproic acid metabolite plays a role in the neurological toxicity.
Placement of a urethral catheter has been recommended to ensure adequate methotrexate elimination in patients with a neobladder; however, the need for this and its impact on methotrexate elimination have not been determined. A 53-year-old man with a cecal continent urinary diversion received intravenous methotrexate 30 mg/m2 on two occasions, with and without urethral catheter drainage of the neobladder. Serum methotrexate concentrations declined at a rate that resulted in 24- and 48-hour values falling below the accepted toxic concentration threshold of 5-50 mumol/L, and 0.05 mumol/L, respectively. In this man, who received low-dose methotrexate, catheterization of the neobladder did not alter methotrexate elimination sufficiently to justify its cost, risk, and inconvenience.