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 achieve 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, which causes bronchi to expand. Of the group of xanthines, theophylline is the most effective bronchodilator.
Theophylline is used, first of all, for the treatment of bronchial asthma. It is rapidly absorbed into the digestive tract, especially when used as a salt or a double salt (aminophylline). The concentration of theophylline in the blood in patients with bronchial asthma depends on the treatment regimen. The maximum concentration in the blood is reached after 60-90 minutes after taking the drug. About 13% of the injected drug is excreted in the urine. The effect of the drug, preventing the appearance of spasm of the bronchi, develops at a drug concentration of more than 10 μg / l, the optimal concentration is 15 μg / l.
Rules of blood sampling for research. Investigate the serum of venous blood. Blood Sampling Time:
- with intravenous administration of the drug:
- 30 minutes after the administration;
- 6 hours after the start of treatment;
- 12-18 hours after the start of treatment;
- at oral reception - in 2 hours after reception and immediately before reception of the next dose.
Toxic effects can develop at concentrations of theophylline 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, agitation. At concentrations above 35 mcg / l - hyperglycemia, lowering blood pressure, tachycardia, arrhythmia, hypoxia, convulsions. The diuretic effect of theophylline contributes to the loss of fluid by the patient's body. As a result, severe dehydration may occur, especially in children.