Normal Reference Ranges
Adult
5.0 - 15.0 mcg/mL
Pediatric
5.0 - 15.0 mcg/mL
Clinical Significance
Bronchodilator with narrow therapeutic index. Toxicity (>20 mcg/mL) causes severe nausea, cardiac arrhythmias (multifocal atrial tachycardia), and grand mal seizures.
Causes of High
- Theophylline toxicity
- CYP1A2 inhibitors (Ciprofloxacin, Erythromycin)
- Fever / illness
Causes of Low
- Subtherapeutic dose
- Smoking (induces CYP1A2)