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Theophylline in serum
Last reviewed: 05.07.2025
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The concentration of theophylline in serum when used in therapeutic doses is 8-20 μg/l (44-111 μmol/l). Toxic concentration is more than 20 μg/l (more than 111 μmol/l).
The half-life of theophylline in adults is 3.5 hours, in children - 8-9 hours, in newborns - 103 hours.
The time to reach the equilibrium state of the drug in the blood (multiple oral doses) in adults is 2 days, in children - 1-2 days, in newborns - 2-6 days.
Theophylline inhibits phosphodiesterase, increases the level of cAMP in cells, is an antagonist of adenosine receptors in the lungs, causing the bronchi to dilate. Of the xanthine group, theophylline is the most effective bronchodilator.
Theophylline is used primarily in the treatment of bronchial asthma. It is rapidly absorbed in the gastrointestinal tract, especially when used in the form of salt or double salt (aminophylline). The concentration of theophylline in the blood of patients with bronchial asthma depends on the treatment regimen. The maximum concentration in the blood is achieved 60-90 minutes after taking the drug. Approximately 13% of the administered drug is excreted in the urine. The effect of the drug, preventing the occurrence of bronchial spasm, develops at a concentration of the drug above 10 mcg / l, the optimal concentration is 15 mcg / l.
Rules for taking blood for research. Venous blood serum is examined. Time for taking a blood sample:
- when administering the drug intravenously:
- 30 minutes after administration;
- 6 hours after the start of treatment;
- 12-18 hours after the start of treatment;
- when taken orally - 2 hours after taking and immediately before taking the next dose.
Toxic effects may develop at theophylline concentrations in the blood exceeding 20 μg/l. At concentrations above 20 μg/l but below 35 μg/l, approximately 75% of patients may develop nausea, vomiting, headache, insomnia, and agitation. At concentrations above 35 μg/l - hyperglycemia, decreased blood pressure, tachycardia, arrhythmia, hypoxia, and seizures. The diuretic effect of theophylline promotes fluid loss by the patient's body. This may result in severe dehydration, especially in children.