theophylline in serum/plasma
Indications
Reference interval
- Therapeutic Range: 10-20 ug/mL
- Toxic Range: >25.0 ug/mL (see theophylline for adverse effects)
Principle
The THEO method uses a single pack rate technique to measure theophylline. The THEO pack contains a particle reagent (PR), which is a latex particle with theophylline linked to the surface. Aggregates of these particles are formed when a theo- phylline- specific monoclonal antibody (Ab) is introduced. Theophylline present in the sample competes with the particles for the antibody, thereby decreasing the rate of aggregation. Hence, the rate of aggregation is inversely proportional to the concentration of theophylline in the sample. The rate of aggregation is measured turbidimetrically at 340 nm. The concentration is determined by means of a previously prepared lot-specific calibration curve or mathematical function.
Theophylline + PR + Ab ----> PR-Ab complex + Theophylline-Ab (absorbs at 340 nm)
Clinical significance
,Theophylline relaxes bronchial smooth muscle to relieve or prevent asthma. The drug is principally eliminated by hepatic metabolism. Theophylline is readily absorbed after oral, rectal, or parenteral administration. If the drug is taken orally without food, the blood concentration peaks within 2 hours. In children & in adults who smoke, the half-life ranges from 3 to 4 hours. Non- smoking adults in good health has an elimination half-life of about 9 hours. ,
Optimal therapeutic effect of theophylline, as evaluated by forced expiratory volume measurements, appears to occur at plasma concentrations of 5-20 ug/mL. Suppression of exercise-induced bronchospasm in the asthmatic patient is optimal at 15 ug/mL. Neonatal apnea treated with theophylline responds to slightly lower concentrations.
Specimen
Patient preparation: No special patient preparation is required.
- Serum is the specimen of choice. Serum is collected in a red top vacutainer by venipuncture. Serum samples can be stored at room temperature for several hours. If frozen at -20 C, serum is stable for at least one year.
- Plasma samples are also acceptable. These samples are collected by venipuncture in a green top vacutainer. Plasma separated from the red cells can be store at room temperature for several hours & frozen for one year.
Minimum sample size 0.6 mL: with an optimum size of 1.5 mL or larger.
More general terms
More specific terms
- theophylline free in serum/plasma
- theophylline in serum/plasma peak
- theophylline in serum/plasma trough
Additional terms
References
- ↑ Kaplan, L., & Pesce, A., Clinical Chemistry:theory, analysis, & correlation, C. V. Mosby Co., St. Louis, MO., 1984, pp. 1389.
- ↑ Tietz, N., Fundamentals of Clinical Chemistry, 3rd edition W. B. Saunders Co., Philadelphia, 1987, pp. 859.
- ↑ Tietz, N., Textbook of Clinical Chemistry, W. B. Saunders Co., Philadelphia, 1986, pp. 1647.
- ↑ ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 1:Operation, DuPont Company, Wilmington, Delaware, 1984.
- ↑ ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 3:Chemistry, DuPont Company, Wilmington, Delaware, 1984.
- ↑ Theophylline Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0090265.jsp