More sensitive high-pressure liquid-chromatographic determiantion of theophylline in serum.

Abstract

We present procedures for determining theophylline in 50 mul of serum. The drug is extracted into a small volume of solvent that contains an internal standard, 8-chlorotheophylline. The extract is Analyzed by isocratic reversedphase chromatography, with measurement of eluted theophylline at 273 nm. Day-to-day reproducibility within 5% is attainable for the concentration range 5--20 mg/liter. Other xanthines and related metabolites do not interfere. Sensitivity is 1 mg/liter. The correlation coefficient, when results by a spectrophotometric procedure were compared, was 0.989. Amobarbital, secobarbital, phenobarbital, and diphenylhydantoin do not interfere. Total analysis time for a single sample is 15 min.

The effect of assay methods on plasma levels and pharmacokinetics of theophylline: HPLC and EIA.

“…# TA-900502) was obtained from Eisai Pharmaceutical Co., Ltd. 8-chlorotheophylline as an internal standard, was purchased from Tokyo Kasei Chemical Co., Ltd. Acetonitrile, chloroform, isopropanol, glacial acetic acid and methanol, all in special reagent grade, were from Wako Pure Chemical Industry, Ltd. It was found that this method can detect as little as 1 gg/ml of plasma theophylline and was confirmed to be identical with the original (Adams et al, 1976).…”

“…The determinations were performed within a week. For assessing the correlation of the drug concentrations between two methods, HPLC (Adams et al, 1976) and EIA (Syva Company, 1977a, b & c), plasma theophylline determinations were undertaken on 254 blood samples obtained from asthmatic in-and out-patients who received the medication in Department of Respiratory Diseases, National Medical Center Hospital, Tokyo.…”

“…A high-pressure liquid-chromatographic method recently established by Adams et al (1976), which had been developed for specific theophylline determination, was used: a HPLC, Hitachi Model 635, was used in conjunction with Hitachi variable wavelength effluent monitor, a 10 mV recorder (Hitachi Model 056), and a reversed phase column, 150 mm x 4 mm i.d. packed with Lichrosorb RP-18 (octadecyl silica).…”

“…During the course of monitoring the plasma level of theophylline in asthmatic adult patients for the past one year in our Division, we discovered that, by using both a high pressure liquid chromatography (HPLC) and a newly developed enzyme immunoassay (EIA) (EMIT@ of Syva Corp., Palo Alto, Calif. 94304, U.S.A., which was supplied by Diichi Chemical Inc., Tokyo as only for investigational use), the analytical methods may lead to different interpretations of theophylline concentrations in asthmatic patients and pharmacokinetics in normal adult men. The purpose of the study to be described here, although obtained from a limited number of subjects, is to determine both the correlations of plasma theophylline concentrations between two analytical methods in patients, and the pharmacokinetic characteristics in normal subjects using the same blood specimen, since we feel that these methods will be of acceptable quality and of wide applicability for plasma level monitoring (Adams, Vandemark & Schmidt, 1976;Syva Company, 1977a & b;Scharpe, Cooreman, Blomme & Laekeman, 1976;Wisdom, 1976).…”

Preparation and evaluation of micro-porous ethylcellulose capsule as oral sustained-release preparation of theophylline

“…Theophylline concentrations were measured by a HPLC method [5]. Briefly, to a 15 mL extraction tube, 100 mL of defrosted plasma sample, 1mL phosphate buffer (pH 6.0) and 5 mL ethylacetate were added.…”