Biomedical subjects

A Dasgupta

Publications and source records attributed to A Dasgupta.

At least 55 records · Page 3Linked to original sources

PubMed2000

Stereospecificity of antibody: quinine, the optical isomer of quinidine and anti-malarial drug chloroquine do not cross-react with quinidine immunoassays.

Quinine is an optical isomer of quinidine. Both quinine and chloroquine (an aminoquinoline derivative) are used in treating malaria. The authors studied cross-reactivity of quinine and chloroquine with the quinidine immunoassays using the TDx and AxSYM analyzers (Abbott Laboratories, Abbott Park, IL). The authors observed no cross-reactivity of chloroquine with quinidine immunoassays (TDx and AXSYM) even when drug-free serum was supplemented with 1000 microg/mL chloriquine. The authors observed no cross-reactivity of quinine up to a concentration of 250 microg/mL. At higher concentrations, the authors observed a small cross-reactivity. The cross-reactivity of a substance should be studied in the presence of the primary analyte. When serum pools prepared from patients receiving quinidine were supplemented with various concentrations of quinine or chloroquine, the authors observed statistically significant declines in quinidine concentrations with higher concentrations of both quinine and chloroquine. The authors observed significant cross-reactivity of L-amphetamine with the amphetamine immunoassay also marketed by Abbott Laboratories and run on the AxSYM analyzer. The authors conclude that although the antibody used in the quinidine assay is stereospecific, the antibody used in the amphetamine assay by the same manufacturer is not stereospecific.

Antibodies↗

PubMed2000

Simultaneous determination of fenfluramine and phentermine in urine using gas chromatography mass spectrometry with pentafluoropropionic anhydride derivatization.

Fenfluramine and phentermine ('fen-phen') are stimulants used primarily for weight loss that have a causative association with serious health problems. Though voluntarily removed from the market by their manufacturers and the FDA in September of 1997, both drugs occasionally reappear in the clinical and forensic setting from individuals who retained old prescriptions, transported the drugs from foreign countries, or 'stockpiled' the medications immediately before their removal from the market. The authors describe an analytical method for simultaneous detection of fenfluramine, phentermine, and the internal standard, N-propylamphetamine, in urine using pentafluoropropionic anhydride derivatization. Detection using and mass spectrometry is described. Baseline resolution of the analytes was achieved in the presence of four other common sympathomimetic amines. The increased molecular weights, better peak profiles, and characteristic fragments containing portions of both derivatizing agent and parent compound aid in the unambiguous identification of these analytes.

Appetite Depressants↗

PubMed2000

Time-dependent absorption of therapeutic drugs by the gel of the Greiner Vacuette blood collection tube.

Stability of therapeutic drugs in sera collected in Becton-Dickinson VACUTAINER serum separator SST tubes has been well studied. Recently, the Greiner Vacuette serum separator tube has become available for blood collection. However, stability of therapeutic drugs in sera when the specimen is collected in the Greiner tube has not been reported. The authors studied the stability of 15 commonly monitored drugs in sera when stored on the gel of the Greiner serum separator tubes. The drugs studied were amikacin, gentamycin, tobramycin, vancomycin, digoxin, quinidine, theophylline, carbamazepine, phenobarbital, phenytoin, valproic acid, tricyclic antidepressants, salicylate, acetaminophen, and ethanol. The authors compared the concentrations of drugs in sera stored in plain tubes (no gel) and in sera stored in the Greiner tubes containing serum separator gel. They observed a significant decline in the concentrations of tricyclic antidepressants when stored in the Greiner tubes. Interestingly, concentrations of amitriptyline declined more than its metabolite nortriptyline and concentration of imipramine also decreased more than its metabolite desipramine. The concentration of carbamazepine also decreased slightly over time when serum was stored in the Greiner tube. Although declines in carbamazepine concentrations on prolonged storage in the Greiner tubes were statistically significant, the decreases may not be clinically significant. The concentrations of the other drugs studied did not decline when stored in the Greiner tubes. The authors conclude that the Greiner brand tube is not suitable for blood collection for analysis of tricyclic antidepressants.

Absorption↗

PubMed2000

Role of Tc-99m MIBI in the evaluation of single pulmonary nodules: a preliminary report.

BACKGROUND: Survival in bronchial carcinoma is closely related to the stage of the disease at the time of diagnosis and a single pulmonary nodule represents a potentially curable stage. This study was conducted to assess the feasibility of using Tc-99m labelled 2-methoxy isobutyl isonitrile (MIBI) to differentiate benign from malignant single pulmonary nodules. METHODS: A prospective study was conducted in the outpatient pulmonary clinic at the Cleveland Clinic Foundation. Twenty five patients with single pulmonary nodules considered indeterminate by their physicians and undergoing a procedure for tissue diagnosis were evaluated by Tc-99m MIBI SPECT scanning prior to definitive testing. Assessment of MIBI uptake was done qualitatively (subjectively) and quantitatively and correlated with the histopathology and nodule size. RESULTS: Of the 21 patients with malignant lesions, 18 had increased uptake of MIBI corresponding to the location of the nodule and were considered positive. The predominant tumour types were large cell (n = 5) and adenocarcinoma (n = 10). All four patients with benign lesions had negative MIBI scans. For malignancy the overall specificity was 100%, sensitivity was 85.7%, positive predictive value was 100%, and negative predictive value was 57%. Quantitative uptake of MIBI correlated with the diameter of the nodule with a correlation coefficient of 0.61 by Spearman's rank sum test. This relationship was statistically significant (p = 0.02). CONCLUSION: This preliminary study suggests that Tc-99m MIBI has a very high specificity and positive predictive value for malignant single pulmonary nodules and might be a useful non-invasive diagnostic modality in their management.

Aged↗

PubMed2000

Positive and negative interference of the Chinese medicine Chan Su in serum digoxin measurement. Elimination of interference by using a monoclonal chemiluminescent digoxin assay or monitoring free digoxin concentration.

An over-the-counter Chinese medicine, Chan Su, is used as a cardiotonic agent. We demonstrated significant digoxin-like immunoreactivity in various organic and aqueous extracts of Chan Su. For example, when a 20-microL aliquot of an aqueous extract of Chan Su powder (1 mg/mL) was added to a 2-mL aliquot of a drug-free serum, the observed digoxin-like immunoreactivity was 2.76 ng/mL (3.53 nmol/L) digoxin equivalent using the fluorescence polarization immunoassay (FPIA). The magnitude of interference was much lower (0.94 ng/mL [1.20 nmol/L]) with the microparticle enzyme immunoassay (MEIA), and no interference was observed with the chemiluminescent assay (CLIA). We also observed a significant positive interference of the extract with the serum digoxin measurement using FPIA. In contrast, we observed a negative interference (falsely lowered digoxin concentration) of the extract in the serum digoxin measurement with the MEIA. The extract had no effect on the serum digoxin measurement with the CLIA. By taking advantage of the high protein binding of Chan Su and only 25% protein binding of digoxin, we further demonstrated that positive interference of Chan Su in the FPIA and negative interference of Chan Su in the MEIA of digoxin could be eliminated by monitoring the free digoxin concentration.

Amphibian Venoms↗

PubMed2000

Mathematical models to calculate fosphenytoin concentrations in the presence of phenytoin using phenytoin immunoassays and alkaline phosphatase.

Under certain circumstances, it is necessary to measure both fosphenytoin and phenytoin concentrations. We describe equations by which fosphenytoin concentrations can be calculated accurately by using phenytoin immunoassays. We supplemented aliquots of drug-free serum with fosphenytoin and measured the phenytoin equivalent concentrations (reading a) using fluorescence polarization immunoassay and a chemiluminescent assay. Then 10 microL of alkaline phosphatase (ALP) solution was added to the specimen, and after incubation for 5 minutes at room temperature, total phenytoin concentration was measured (reading b). ALP completely converts fosphenytoin to phenytoin in 5 minutes. Therefore, the delta reading (b-a) represents increased observed value due to complete conversion of fosphenytoin to phenytoin for a particular fosphenytoin concentration. By using the x-axis as the delta reading and the y-axis as the target fosphenytoin concentrations, we observed equations that can be used to calculate the concentration of fosphenytoin in the presence of phenytoin. To test the validity of our equations, we prepared 2 serum pools from patients receiving phenytoin and supplemented them with known concentrations of fosphenytoin. Then initial (reading a) and final (after addition of ALP and incubation, reading b) concentrations were measured by immunoassay. We can accurately predict fosphenytoin and phenytoin concentrations from the delta reading.

Alkaline Phosphatase↗

PubMed2000

Cytokine mRNA expression and serum cortisol evaluation during murine lung inflammation induced by Mycobacterium tuberculosis.

A model system was characterized for investigating the potential role of cortisol in MTB induced immunopathology. Serum cortisol levels were evaluated in two mouse strains; C57BL/6 mice develop lung granulomas following acute Mycobacterium tuberculosis infection while A/J mice are deficient in this process. Serum cortisol levels were examined post infection, as well as immunoregulatory mRNA expression in the lung, measured using bioluminescent RT-PCR techniques. Prior to infection, the A/J mice constitutively maintain nearly 75&percent; higher serum cortisol than C57BL/6 mice. Both A/J and C57BL/6 mice exhibited approximately 30&percent; reduction in relative serum cortisol following infection. At no time did serum cortisol levels in the A/J fall below constitutive levels in the non-infected C57BL/6. The overall elevated cortisol in the A/J may affect pulmonary immunoresponsiveness; A/J mice exhibited earlier induction of IL-10 and TNF-alpha than C57BL/6 mice, with a relative lack of IL-2 during late infection. Conversely, the C57BL/6 mice demonstrated higher IL-12(p40) and IL-2 messages at the latter stages of disease than the A/J mice. Both mice demonstrated high IFN-&gama; mRNA. The high constitutive serum cortisol in the A/J mice may therefore contribute to establishment of an environment counter-productive to initiation of protective Th1 cell and granulomatous responses.

Animals↗

PubMed2000

Performance evaluation of a new chemiluminescent cardiac troponin I assay.

Cardiac troponin I is a marker for diagnosis of myocardial damage. Several immunoassays are currently available for determination of concentrations of troponin I in serum. We evaluated a chemiluminescent assay for troponin I using ACS:180 automated analyzer (Bayer Diagnostics). We compared our results with two other immunoassays using the OPUS Magnum (OPUS troponin I assay, Dade Behring) and AxSYM (microparticle enzyme immunoassay, Abbott) analyzers. The within-run and between-run CVs were less than 5% for all three levels of controls. The chemiluminescent assay for troponin I was linear up to a serum troponin I concentration of 50 ng/mL and the detection limit was 0.1 ng/mL of troponin. A good correlation between troponin I concentration measured by the chemiluminescent assay (y axis) and the microparticle enzyme immunoassay (MEIA) (x axis) was observed, although the concentrations of troponin I in individual specimens were approximately four times higher, when measured by the MEIA assay, than those measured by chemiluminescent assay. The correlation coefficient was 0.98 with the regression equation y = 0.22x + 1.125. We also observed a good correlation in troponin I concentrations obtained by the chemiluminescent assay (y axis) and OPUS troponin I assay (x axis). The correlation coefficient was 0.96 and the regression equation was y = 0.79x - 0.52. The correlation coefficient was 0.93 when we compared troponin I concentrations obtained by the OPUS assay (x axis) with the corresponding concentrations obtained by the MEIA assay (y axis). The corresponding regression equation was y = 0.25x + 3.5. We conclude that the chemiluminescent troponin I assay showed good analytical performance.

Humans↗

PubMed1999

Structure and function of a small RNA that selectively inhibits internal ribosome entry site-mediated translation.

A 60 nt long RNA termed IRNA, isolated from the yeast Saccharomyces cerevesiae, was previously shown to selectively block internal ribosome entry site (IRES)-mediated translation without interfering with cap-dependent translation of cellular mRNAs both in vivo and in vitro. IRNA specifically bound cellular proteins believed to be important for IRES-mediated translation. We demonstrate here that a complementary copy of IRNA (cIRNA) is also active in blocking IRES-mediated translation and that it binds many of the same cellular proteins that IRNA does. We have probed the secondary structure of both IRNA and cIRNA using single-strand- and double-strand-specific nucleases as well as using oligonucleotide hybridization followed by RNase H digestion. Both IRNA and cIRNA share secondary structural homology, although distinct differences do exist between the two structures. Mutational analysis of IRNA shows that sequences that form both the main stem and one loop are critical for its translation inhibitory activity. Maintenance of the established secondary structure appears to be required for both IRNA's ability to bind cellular trans -acting proteins believed to be required for IRES-mediated translation and its ability to block IRES-mediated translation.

Computer Simulation↗

PubMed1999

Significantly improved oral uptake of amikacin in FVB mice in the presence of CRL-1605 copolymer.

Amikacin is an aminoglycoside which is used in the treatment of infection from gram negative bacteria. Amikacin is also used synergistically with penicillin against gram positive cocci. Amikacin cannot be delivered orally probably due to efflux of drug by P-glycoprotein pump in the brush border of intestine. We studied the possibility of delivering amikacin orally in mice using a copolymer (CRL-1605) as a vehicle. This copolymer inhibits P-glycoprotein pump. Two different doses of amikacin were used (500 mg/kg and 100 mg/kg). The concentration of polymer used was 132 mg/kg. The liquid formulation was fed to mice by gavage and serum amikacin concentrations were estimated after one hour and two hours using fluorescence polarization immunoassay. We observed a two fold increase in serum amikacin concentration when amikacin was orally delivered in the presence of CRL-1605 compared to controls (amikacin alone). We conclude that gastrointestinal absorption of amikacin is significantly increased in the presence of CRL-1605 in mice.

Administration, Oral↗

PubMed1999

Transbronchial needle aspiration. An underused diagnostic technique.

Despite its proven usefulness, TBNA is not widely used. An American College of Chest Physicians (ACCP) survey showed that only 11.8% of pulmonologists use TBNA. Most pulmonologists in the 1980s were not formally trained in TBNA. This lack of training has unfortunately translated to minimal emphasis on TBNA in current training programs in a large number of institutions. Technical problems with the procedure (faulty site selection, incomplete needle penetration, catheter kinking that prevents adequate suction, etc.), the confusing array of needles, low diagnostic yields, unproven concerns regarding the safety of the procedure, inadequate cytopathology support, and bronchoscopic damage have all perpetuated the image of limited usefulness for this procedure. Limitations to the practice of TBNA are: Lack of training during fellowship Technical inadequacies Lack of cytopathologists trained in TBNA interpretation Fear of bronchoscope damage Safety issues Failure to reproduce published successes Reservations regarding usefulness of TBNA results Hands-on experience with TBNA, developing familiarity and expertise with only a few needles, and paying careful attention to anatomy, procedure techniques, and specimen acquisition may all help to increase yield. The following lists how better results can be obtained with TBNA: Preprocedure Review TBNA instruction tapes Attend hands-on courses Practice with lung models Review patient's CAT scans Familiarize with one-two cytology and histology needle Obtain a trained assistant Procedural Identify target site Needle to airway angle at least greater than 45 degrees Insert entire length of the needle Use scope channel to support the catheter Release suction before withdrawing needle (for staging) Specimen acquisition Avoid delay in preparing slides Adequate sampling (at least two) Use smear method for cytology specimen Analyze all samples flush solutions cell block Postprocedure Find an experienced cytopathologist Review your procedure (by watching video) Review pathology slides Acquisition of skills with cytology needles should precede the use of the histology needle. Increasing education and experience can also increase diagnostic yields. Transbronchial needle aspiration has been proven to be accurate in staging lung cancers, identifying inoperable carcinomas, and diagnosing a variety of lung diseases. Few complications have been encountered and the technique is less invasive and less costly than surgical procedures. Drawing on evidence from published literature, we suggest the following guidelines for TBNA: All patients presenting with mediastinal or hilar adenopathy or both, should have 22-ga and/or 19-ga TBNA as the initial procedure. These procedures would help diagnose malignant and nonmalignant diseases, and stage lung cancers. All patients with evidence of submucosal and peribronchial disease should have 22-ga needle cytology sampling. In patients with visible endobronchial disease, 22-ga TBNA should be optional. In the presence of a necrotic or a hemorrhagic tumor, or in a patient with a bleeding diathesis, TBNA would be helpful. In all patients with Type III and IV peripheral nodules, TBNA should be the initial diagnostic procedure. There remains no doubt about the diagnostic usefulness of TBNA. Guidelines must be developed to ensure that pulmonary fellows are adequately trained in this procedure. Regional workshops with hands-on experience targeted to practicing pulmonologists organized by the ACCP would help popularize the procedure. Initial low yields should not discourage pulmonologists from using the procedure. Collaboration between thoracic surgeons, oncologists, and pulmonary physicians is essential to set up TBNA programs within institutions. With time, as more and more pulmonologists attain expertise in TBNA, the full potential of this nonsurgical, cost-effective, and safe procedure will be realized.

Biopsy, Needle↗

PubMed1999

Airway stents.

Considerable progress has been made since the initial stents were manufactured. Despite the reported side effects, cumulative evidence suggests beneficial effects in properly selected patients. The technology is still in evolution, and design modifications strive to find the perfect stent. The Dumon stent remains the gold standard against which the functions of all other stents are being measured. Unfortunately requirement for the RB for deployment has restricted widespread application at least in the United States. The Wallstent can be inserted using FB and has a great potential among the metal stents. Its biggest drawback is that once inserted it is difficult to remove. Studies with the nitinol Ultraflex and the polyester/silicone Polyflex prototype stent also show promise, although extensive experience and long-term follow-up data are still not available. It is possible that combining the strength of the tube stents with the flexibility of the metal stents may one day help to develop the ideal stent.

Airway Obstruction↗

PubMed1999

Suppression of total digoxin concentrations by digoxin-like immunoreactive substances in the MEIA digoxin assay. Elimination of negative interference by monitoring free digoxin concentrations.

Digoxin-like immunoreactive substances (DLIS) cross-react with antidigoxin antibody and falsely elevate immunoassay-measured total digoxin concentrations. The fluorescence polarization immunoassay (FPIA) for digoxin showed high cross-reactivity with DLIS, but a new microparticle enzyme immunoassay (MEIA) had low cross-reactivity. The concentration of digoxin in the presence of DLIS was falsely lowered (negative interference) when measured by MEIA. We prepared the following serum pools: 2 normal (no DLIS), 2 from patients with uremia, and 3 from patients with liver disease (high DLIS). No patients received digoxin or digitoxin. When normal pools were supplemented with known concentrations of digoxin, total and free concentrations measured by both assays were comparable, but when liver and uremic pools containing high DLIS were supplemented with digoxin, the measured total digoxin concentrations were lower by MEIA and higher by FPIA. However, by taking advantage of 25% protein binding of digoxin and high protein binding of DLIS, free digoxin levels were not affected by DLIS. In 2 patients receiving digoxin but without volume expansion, total and free digoxin concentrations measured by both assays were comparable; in the 2 volume-expanded patients, only free digoxin concentrations were comparable. Monitoring free digoxin concentration can eliminate negative interference of DLIS in the MEIA for digoxin.

Cross Reactions↗

PubMed1999

Use of alkaline phosphatase to correct the underestimation of fosphenytoin concentration in serum measured by phenytoin immunoassays.

The pharmacologic activity of fosphenytoin, a new phosphate ester pro-drug of phenytoin, is due to in vivo conversion to phenytoin. Fosphenytoin concentrations cannot be accurately estimated by phenytoin immunoassays (fluorescence polarization and chemiluminescence) owing to the nonlinear relation between fosphenytoin concentration and the observed cross-reactivity. The problem of slow conversion of fosphenytoin to phenytoin in serum in vitro can be circumvented by rapidly converting fosphenytoin to phenytoin in vitro by alkaline phosphatase. Drug-free serum, heparin, EDTA, or citrated plasma were supplemented with 2 concentrations of fosphenytoin. Then to 1-mL aliquots of specimen, no enzyme (control), 10 microL, or 25 microL of enzyme solution was added. The specimens were incubated, and phenytoin concentrations were measured by fluorescence polarization and chemiluminescent assays. In the absence of enzyme, we observed little conversion of fosphenytoin to phenytoin, but in the presence of only 10 microL of enzyme, the conversion of fosphenytoin to phenytoin was complete in 5 minutes. We also observed complete conversion of fosphenytoin to phenytoin by alkaline phosphatase in heparin, EDTA, and citrated plasma. If clinically indicated, the phenytoin concentration can be measured before and after addition of enzyme to roughly estimate the rate of conversion.

Alkaline Phosphatase↗

PubMed1999

False-positive troponin I in the MEIA due to the presence of rheumatoid factors in serum. Elimination of this interference by using a polyclonal antisera against rheumatoid factors.

We report false-positive cardiac troponin (cTn) I results in the microparticle enzyme immunoassay (MEIA) using the AxSYM analyzer. We studied serum samples from 12 patients with positive rheumatoid factor but with no indication of myocardial infarction (MI); 2 also had positive antinuclear antibody (ANA) titers. Serum samples from 7 patients with positive ANA titers and negative rheumatoid factors also were studied. Total creatine kinase (CK) was run using a Hitachi 747 analyzer, cTnT using an Elecsys 2010 analyzer, and cTnI and CK-MB using an AxSYM analyzer. We observed no measurable cTnI and cTnT concentrations in 12 control samples or in specimens with positive ANA titers and negative rheumatoid factors. In contrast, samples from 7 of 12 patients containing rheumatoid factors had measurable cTnI concentrations. Four specimens showed cTnI concentrations more than 2.0 micrograms/L, the suggested diagnostic cutoff for MI. None of the specimens showed detectable cTnT. The concentrations of total CK and CK-MB were within normal ranges in all specimens. False-positive results were observed only with the MEIA for cTnI. This interference can be eliminated by using a polyclonal antisera against rheumatoid factor. The chemiluminescent assay for cTnI showed no detectable cTnI concentration in any specimen.

Antibodies, Antinuclear↗

PubMed1999

Gas chromatographic/mass spectrometric identification and quantification of aniline after extraction from serum and derivatization with 4-carbethoxyhexafluorobutyryl chloride, a new derivative.

Aniline, widely used as an intermediate in the synthesis of dye, is also used in the manufacture of pharmaceuticals, photographic developers, shoe polish, and other common substances. Exposure to aniline is toxic because it produces methemoglobin. Aniline levels are usually not measured in serum; in humans, blood methemoglobin levels are often measured as an index of exposure to aniline. In this article, we describe a method for the identification and the quantification of aniline by gas chromatography/mass spectrometry (GC/MS) after its extraction from human serum and derivatization with 4-carbethoxyhexafluorobutyryl chloride. Aniline, as well as the internal standard N-methyl aniline, was extracted from alkaline serum using chloroform. Aniline and the internal standard were derivatized with 50 microL of 4-carbethoxyhexafluorobutyryl chloride. After evaporating the excess derivatizing reagent, the residue was reconstituted in 50 microL of ethyl acetate and injected into the GC/MS. A positive identification of derivatized aniline can be made from the strong molecular ion at m/z 343. Similarly, derivatized internal standard showed a strong molecular ion at m/z 357. The within-run and between-run precisions of the assay were 3.8% and 5.8%, respectively, at an aniline concentration of 5 mg/L. The assay was linear for serum aniline concentrations of 0.5 mg/L to 25.0 mg/L. The detection limit was 0.1 mg/L. The assay was not affected by lipemia, hemolysis, or high bilirubin concentration in serum, and the assay was applicable to whole blood. We also fed mice (C57bl/6) with various concentrations of aniline and measured methemoglobin and blood concentrations of aniline. The methemoglobin percentage and aniline concentrations in blood increased with increasing aniline doses.

Aniline Compounds↗

PubMed1999

Effect of digoxin fab antibody on the measurement of total and free digitoxin by fluorescence polarization and a new chemiluminescent immunoassay.

Digoxin fab antibody (Digibind; Burroughs Wellcome, Research Triangle Park, NC, USA) is used in the treatment of digoxin overdose. The effect of digibind on the measurement of total and free digoxin has been extensively studied. However, the effect of digibind on digitoxin measurements has not been studied thoroughly. The authors studied the effect of digibind on the measurement of total and free digitoxin in vitro using the fluorescence polarization immunoassay and a new chemiluminescent immunoassay. We also studied the capability of digibind to bind digitoxigenin, the major aglycon metabolite of digitoxin. Digibind neutralized both digitoxin and digitoxigenin in vitro, as evidenced by significant reductions in free digitoxin and digitoxigenin (measured as digitoxin equivalent) concentrations. Digibind caused negative interference in the measurement of total digitoxin concentrations by both fluorescence polarization and chemiluminescent assays. However, the magnitude of negative interference was significantly higher with the chemiluminescent assay. For example, in a serum pool supplemented with 80 ng/mL of digitoxin, the concentrations of total and free digitoxin measured by the fluorescence polarization immunoassay were 82.1 ng/mL and 3.3 ng/mL respectively. In the presence of 5 microg/mL of Digibind, the corresponding total and free digitoxin concentrations were 73.9 ng/mL and none detected, respectively. In another serum pool supplemented with 70 ng/mL of digitoxin, the concentrations of total and free digitoxin as measured by the chemiluminescent assay were 69.1 ng/mL and 3.8 ng/mL, respectively. In the presence of 5 microg/mL of Digibind, the corresponding total and free digitoxin concentrations were 29.0 ng/mL and none detected, respectively. Because this effect may also occur in vivo, the progress of Digibind therapy in treating a patient with digitoxin overdose may be monitored by measuring the free digitoxin concentrations.

Cardiotonic Agents↗

PubMed1999

Effect of heating human sera at a temperature necessary to deactivate human immunodeficiency virus on measurement of free phenytoin, free valproic acid, and free carbamazepine concentrations.

Minimizing the risk for infection to laboratory staff from a contaminated blood sample is a major safety goal in the clinical laboratory. One dangerous pathogen, the human immunodeficiency virus (HIV), can be deactivated by heating sera at 56 degrees C for 30 minutes. The authors previously reported that if serum was subjected to those conditions, the concentrations of the nine most commonly monitored drugs were not altered, whereas phenytoin and carbamazepine concentrations were reduced slightly. Monitoring free phenytoin, free valproic acid, and free carbamazepine concentrations is strongly recommended for patients with uremia, liver disease, and hypoalbuminemia. Because drug protein binding can be affected by temperature, the authors investigated the effect on free drug concentrations of sera heated to levels necessary for deactivation of the HIV virus. They measured total and free drug concentrations in serum pools prepared from patients receiving phenytoin, valproic acid, and carbamazepine. Serum pools were heated at 56 degrees C for 30 minutes and then brought to room temperature. The total and free drug concentrations were measured immediately after heating and then at 20- and 45-minute intervals. The concentrations of free phenytoin and free valproic acid were significantly higher after heat treatment. However, after equilibration of sera at room temperature for 20 minutes, the free concentrations of phenytoin were comparable to preheating values, although total phenytoin concentrations (Serum Separator Tubes) were reduced slightly. In contrast, free valproic acid concentrations did not return to the original levels even after 45 minutes. Free carbamazepine concentrations did not change even immediately after heating. However, total carbamazepine concentrations were reduced slightly when sera were heated in serum separator tubes (SST Tubes).

Anticonvulsants↗