Theophylline
Theophylline is one of the therapeutic drugs used to treat asthma and chronic obstructive pulmonary disease. In recent years, theophylline has been replaced in adult therapy by steroid and beta-adrenergic bronchial inhalers. Theophylline is still used as a second or third line therapy in adults where steroidal therapy has failed and the patient is in acute respiratory distress. It is also used to treat patients on mechanical ventilation, patients with structural asthma, patients with chronic respiratory failure and pediatric asthma.
Because fat stores are poorly accessible to theophylline, dosage should be calculated based on lean or ideal body weight rather than actual body weight. Approximately two days of treatment are required to reach steady state levels in adults. This time is decreased in patients who smoke and increased in patients with cardiac and hepatic failure. Children require one to two days to reach steady state levels, while newborns require approximately five days. Serum concentrations can be measured to optimize therapy. Trough values for dosage adjustment should be drawn 8 to 12 hours after an oral dose or 4 to 6 hours after beginning an IV infusion. Theophylline concentrations exhibit a circadian rhythm with higher concentrations occurring in the morning. It is important to consistently draw blood samples at the same time of the day in order to compare results.
Minor side effects that may occur early in treatment and then subside include headache, nausea, vomiting, nervousness, and insomnia. Acute or chronic overdose may be characterized by similar symptoms as well as tremor, convulsions, tachycardia, diarrhea, cardiac arrhythmias, and cardiorespiratory arrest. If toxicity is suspected, a blood sample should be drawn immediately. Monitoring usually continues until serum levels are less than 20 ug/mL.
Therapeutic range is 10?20 ug/mL. Levels higher than 20 ug/mL are considered critical values.
Specimen requirement is one plain red top tube of blood.
