Measurement Of Theophylline In Serum Research Articles

Serum theophylline after multiple dosing with transdermal gels in cats.

Our objectives were, first, to determine if therapeutic serum theophylline concentrations could be achieved using long-term, once-daily dosing of transdermal theophylline and, secondarily, to evaluate the difference between two transdermal theophylline formulations. Seven healthy cats, 1-10 years of age, were evaluated in a two-way, randomized, double-blinded, crossover study. Participants received transdermal theophylline at 15 mg/kg for 21 days in either pluronic lecithin organogel (PLO) or Lipoderm formulation. On day 22, blood was collected 2, 6, 14 and 24 h after dosing. After a 14 day washout period, blood was collected to verify non-detectible theophylline concentrations. The alternate formulation was administered for 21 days, and sampling was repeated. Serum theophylline concentrations were determined using an automated immunoassay. Serum concentrations were compared between formulations using a two-way random-measures ANOVA and over time within a formulation using a repeated-measures ANOVA. Therapeutic serum theophylline concentrations were achieved for 2/7 cats in each group. Of 56 serum theophylline measurements obtained, only seven (13%) were within the therapeutic range. No significant difference was detected in drug concentrations achieved by the transdermal formulations at any time point. In addition, no significant difference in serum theophylline concentrations was noted between time points for PLO ( P = 0.751) or Lipoderm ( P = 0.107). Once-daily transdermal dosing of theophylline does not reliably achieve therapeutic concentrations. Individual cats may achieve therapeutic concentrations. No significant difference was noted between PLO and Lipoderm formulations. Therefore, transdermal theophylline formulations should not be considered as a first-line therapy in feline asthma patients.

Amperometric enzyme electrode for determination of theophylline in serum

This paper describes an amperometric enzyme electrode for the rapid determination of theophylline in serum. The method is based on the catalysed oxidation of theophylline by the haem-containing enzyme theophylline oxidase. Results are presented for two approaches. First, ferrocene monocarboxylic acid was used as a mediator. The second-order rate constant was 1·1 × 10 3 1 mol −1 s −1. Secondly, the organic conducting salts NMP.TCNQ was used to construct enzyme electrodes. These electrodes were employed for the rapid (60 s) measurement of theophylline in serum at a working potential of +100 mV versus Ag/AgCl. Linear calibration curves were obtained over the clinically relevant range ( y = 0.13 x + 0.22, n = 8). Caffeine, theobromine and 3-methyl-xanthine at levels up to 100 mg l −1 do not interfere and 1-methylxanthine shows cross-reactivity at concentrations greater than 50 mg l −1.

Evaluation of Chromatographic and Kit Immunoassay Techniques for the Measurement of Theophylline in Serum

The accuracy and precision of assay techniques used to measure theophylline concentrations in human serum were compared using data from 96 samples from the Heathcontrol external quality assurance scheme. Abbott TDX had the highest precision, with a mean coefficient of variation (CV) of measurements of 6.4%, and Ames Fluorostat was most accurate, with a mean bias of +0.1%. Differences between the better techniques, however, were not significant. The Beckman ICS assay gave the lowest precision (CV 9.3%) and, in addition, produced the highest proportion (7.5%) of rejected observations greater than 3 standard deviations from the sample mean. The least accurate method was radioimmunoassay, with a -9.9% bias. Measurements from two samples spiked with paraxanthine demonstrated that 76% of laboratories using high-pressure liquid chromatography (HPLC) were unable to distinguish between paraxanthine and theophylline. The +4% bias observed at low concentrations and the high variability (CV 8.3%) of measurements made by HPLC were thus attributed to interference by paraxanthine present in the sample matrix. Discriminant analysis of a range of HPLC column and mobile phase parameters indicated that separation of theophylline and paraxanthine was achieved by the use of lower flow rates with mobile phases of solvent mixtures with lower proton donator selectivity.

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We evaluated the particle-enhanced turbidimetric inhibition immunoassay (PETINIA) for the measurement of theophylline in serum. The coefficients of variation in both within-day (n= 10) and between-day (n=10) precision studies were less than 4 %, and the analytical recoveries were 98-103% at the concentrations of 5, 10 and 20μg/ml of theophylline. Good correlations were observed among assay results by PETINIA, high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA) for 120 serum specimens cbllected from patients with chronic obstructive pulmonary disease receiving theophylline therapy.The regression lines obtained were: PETINIA =1.034 x HPLC -0.404 (r =0.994, Sy/x=0. 57μg/ ml), PETINIA =1.037 x FPIA-0.539 (r=0.995, Sy/x=0.51μg/ml). The cross reactivity in PETINIA was also studied with 11 compounds structurally related to theophylline. None of these compounds exhibited significant cross reactivity (less than 5 %) except for 1, 3-dimethyluric acid (11%). From these results, we could conclude that PETINIA is a useful method for therapeutic monitoring of serum theophylline having good precision and accuracy, and high specificity.

Ligand displacement immunoassay: a novel enzyme immunoassay demonstrated for measuring theophylline in serum.

We describe a ligand displacement immunoassay for measurement of theophylline in serum or plasma and show it to be clinically useful. A conjugate of theophylline-specific antiserum covalently bound to micro-crystalline cellulose and a beta-galactosidase-labeled theophylline derivative is prepared as a lyophilized reagent. Sample is added to the conjugate and, after 5-min incubation at room temperature, the bound and displaced enzyme-ligand are separated by brief centrifugation. The enzyme activity of the displaced enzyme-ligand is measured on a spectrophotometer or centrifugal analyzer. Linear calibration curves are obtained with appropriate sample dilution, allowing generation of the standard curve with a saline zero reference and a single calibrator. Performance of the assay compares favorably with that of other theophylline assays; comparison studies with use of 145 clinical specimens gave a coefficient of correlation with EMIT of 0.97.

Practical Considerations in the Safe and Effective Use of Theophylline

Theophylline is the most widely prescribed drug for treatment of asthma in the United States. In order to use theophylline effectively and safely, the physician must appreciate factors influencing absorption, distribution to body tissues, metabolism, and elimination of the drug. Since both efficacy as a bronchodilator and toxicity are related to serum concentration, measurement of theophylline in serum has proved useful in optimizing therapy. Much still needs to be learned in regard to the concentration of theophylline in serum for optimal bronchodilator activity. It is important to treat the patient and not the serum concentration.

Micro-scale extractive alkylation procedure for the gas-chromatographic measurement of theophylline in serum and saliva, with use of a nitrogen detector.

In this 10-min gas-chromatographic assay for theophylline, a 25-microliter portion of serum or saliva sample, 100 microliter of extraction reagent, and 1.0 ml of solvent were mixed, the solvent separated and evaporated, and an aliquot of the reconstituted extract injected into the gas chromatograph. At a concentration of 11 mg/liter, within-run precision (CV) was 3.6% and run-to-run 2.9%. At 22 mg/liter, within-run precision was 2.8%. Concentration and instrument response are linearly related between 2 and 40 mg/liter. The limit of detection was 0.4 mg/liter. Results correlated well (r = 0.98) with those by another micro-scale gas-chromatographic procedure. Analytical recovery was estimated to exceed 90%, and no interferences from other xanthines or related drugs were observed.

Guide to Oral Theophylline Therapy for the Treatment of Chronic Asthma

Theophylline, when used appropriately, seems to be the most effective noncorticosteroid prophylactic medication for chronic asthma. Dosage, however, requires consideration of the relationship between serum concentration, efficacy, and toxicity, in addition to the variability in rates of elimination. Therapy is initiated with 16 mg/kg/day or 400 mg/day (whichever is less) in divided doses at appropriate intervals depending on the rate of absorption of the product used. If side effects are absent, the dosage is increased at three-day intervals until the age-related mean dosage necessary to produce a therapeutic level, is reached. Final dosage adjustment is generally based on a single determination of serum concentration; dosage requirements generally then remain constant for six to 12 months depending upon the child's growth rate. Dosage adjustment in this manner optimizes benefit, minimizes risk of toxic effect, and avoids excessive numbers of serum theophylline measurements.

Oral theophylline dosage for the management of chronic asthma

Theophylline dosage requirements to maintain serum concentrations of 10 to 20 microgram/ml among asthmatic patients were examined in 156 children, ages 2 1/2 months to 16 years, and 33 otherwise health adults. Using 100% bioavailable preparations, low doses were used initially and increased, if tolerated, at three-day intervals. Final dosage was based on serum theophylline measurements which were subsequently repeated after six or more months of therapy. Dosage standardized by weight averaged 24.1 +/- 5.5 mg/kg/day (mean +/- SD) among the 77 children under age 9 years. Age-related variability of weight-adjusted doses were not observed for younger children, but average dose requirements decreased progressively beyound age 9 years to 13 mg/kg/day for patients beyoung 16 years of age. Although interpatient variability in dosage was confirmed at all ages, intrapatient variability in requirements over an average eight-month interval were small; dosage changes to maintain therapeutic serum concentration were primarily associated with growth. These data allow age-specific guidelines for dosage recommendations based on the likelihood of optimally effective and potentially toxic serum theophylline concentrations.

COMPARISON OF CROMOGLYCATE (CROMOLYN) AND THEOPHYLLINE IN CONTROLLING SYMPTOMS OF CHRONIC ASTHMA: A Collaborative Study

28 children with chronic asthma (15 in Denver and 13 in London) completed a 12 wk double-blind trial of treatment with sodium cromoglycate (cromolyn sodium), theophylline, and a combination of both. The three regimens were administered, each for 4 wk, in random sequence as part of a collaborative investigation of the relative efficacy of the two antiasthmatic agents. Cromoglycate was administered by inhalation in standard doses of 20 mg q.i.d. Theophylline dosage was individualised with the assistance of serum-theophylline measurements and averaged 6 mg/kg/dose q.i.d. (range 3·8-8·5 mg/kg/dose). Peak expiratory-flow rates measured twice daily on all patients averaged 75% of that predicted during cromoglycate administration, 79% during theophylline, and 81% during the combined-drug regimen (P <0·05). Patients had an average of 59% of days free of symptoms while on cromoglycate and 71% of days symptom-free when on both the theophylline and the combination regimens (P <0·025). None of the 13 patients whose asthmatic symptoms were previously controlled with cromoglycate was unable to complete the 4 wk trial with theophylline alone; 1 patient whose symptoms had been previously controlled with theophylline twice developed severe asthmatic symptoms while receiving cromoglycate, and he had to be withdrawn from that study period. No significant differences in adverse effects of the medication were observed during the 12 wk trial.

Improved theophylline serum analysis by an appropriate internal standard for gas chromatography

A gas chromatographic method is presented for the measurement of theophylline in serum. To serum samples containing the drug the internal standard, 3-isobutyl-l-methylxanthine, was added and the serum was saturated with ammonium carbonate. A mixture of isopropanol-chloroform (5:95) was used for extraction. The organic phase was filtered and evaporated. The residue, dissolved in chloroform, was extracted with sodium hydroxide. The basic solution was acidified, washed with hexane and re-extracted with isopropanol-chloroform. The organic phase was dried with anhydrous sodium sulphate before evaporation. The sample was derivatized with n-Butyl-8 reagent. 85% of theophylline was recovered by extraction. 3-Isobutyl-l-methylxanthine was recovered with the same efficiency as theophylline and gas chromatographed well. The standard curve was linear between 1.0 and 50.0 μg/ml theophylline. No interference was encountered from normal serum constituents or methylxanthines such as caffeine, theobromine, or 3-methylxanthine. Serum samples were stored in the refrigerator for two weeks without significant loss of drug. The precision and accuracy of the method were good.

Clinical Evaluation of Elixophyllin with Correlation of Pulmonary Function Studies and Theophylline Serum Levels in Acute and Chronic Asthmatic Patients

This paper describes an amperometric enzyme electrode for the rapid determination of theophylline in serum. The method is based on the catalysed oxidation of theophylline by the haem-containing enzyme theophylline oxidase. Results are presented for two approaches. First, ferrocene monocarboxylic acid was used as a mediator. The second-order rate constant was 1·1 × 103 1 mol−1 s−1. Secondly, the organic conducting salts NMP.TCNQ was used to construct enzyme electrodes. These electrodes were employed for the rapid (60 s) measurement of theophylline in serum at a working potential of +100 mV versus Ag/AgCl. Linear calibration curves were obtained over the clinically relevant range (y = 0.13x + 0.22, n = 8). Caffeine, theobromine and 3-methyl-xanthine at levels up to 100 mg l−1 do not interfere and 1-methylxanthine shows cross-reactivity at concentrations greater than 50 mg l−1.