 , Agents that reduce seizure threshold , Alkaloids , Anti-Asthmatic Agents , Autonomic Agents , Bronchodilator Agents , Cardiovascular Agents , Cytochrome P-450 CYP1A2 Substrates , Cytochrome P-450 CYP1A2 Substrates with a Narrow Therapeutic Index , Cytochrome P-450 CYP2C8 Substrates , Cytochrome P-450 CYP2D6 Substrates , Cytochrome P-450 CYP2D6 Substrates with a Narrow Therapeutic Index , Cytochrome P-450 CYP2E1 Substrates , Cytochrome P-450 CYP2E1 Substrates with a Narrow Therapeutic Index , Cytochrome P-450 CYP3A Substrates , Cytochrome P-450 CYP3A4 Substrates , Cytochrome P-450 CYP3A4 Substrates with a Narrow Therapeutic Index , Cytochrome P-450 Substrates , Drugs for Obstructive Airway Diseases , Enzyme Inhibitors , Heterocyclic Compounds, Fused-Ring , Narrow Therapeutic Index Drugs , Neurotransmitter Agents , Peripheral Nervous System Agents , Phosphodiesterase 5 Inhibitors , Phosphodiesterase Inhibitors , Purinergic Agents , Purinergic Antagonists , Purinergic P1 Receptor Antagonists , Purines , Purinones , Respiratory Smooth Muscle Relaxants , Respiratory System Agents , Vasodilating Agents , Xanthine derivatives , Xanthines and Adrenergics