Ephedrine (l-form) is an alkaloid, which was initially purified from Ephedra plant. The extract form Ephedra has been used in China for medicinal purposes for several thousand years. Ephedrine acts as an agonist at alpha- and beta-adrenergic receptors and indirectly causes the release of norepinephrine from sympathetic neurons. The drug crosses the blood brain barrier and stimulates the central nervous system. Ephedrine products are now banned in many countries, as they are a major source for the production of the addictive compound methamphetamine. FDA has approved ephedrine only for the treatment of clinically important hypotension occurring in the setting of anesthesia.

Levalbuterol is the (R)-enantiomer of the drug substance racemic albuterol (salbutamol). Binding studies have demonstrated that (R)-albuterol binds to the beta2-adrenergic receptor with a high affinity, whereas (S)-albuterol binds with 100-fold less affinity than (R)-albuterol. Other evaluations have suggested that (R)-albuterol possesses the bronchodilatory, bronchoprotective, and ciliary-stimulatory properties of racemic albuterol, while (S)-albuterol does not contribute beneficially to the therapeutic effects of the racemate and was originally assumed to be inert. Xopenex (levalbuterol HCl) Inhalation Solution is indicated for the treatment or prevention of bronchospasm in adults, adolescents, and children 6 years of age and older with reversible obstructive airway disease.

Ipratropium (ipratropium bromide, ATROVENT® HFA) is a muscarinic antagonist structurally related to atropine but often considered safer and more effective for inhalation use. It is indicated for the maintenance treatment of bronchospasm associated with chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema. Ipratropium (ipratropium bromide, ATROVENT® HFA) is an anticholinergic (parasympatholytic) agent which, based on animal studies, appears to inhibit vagally-mediated reflexes by antagonizing the action of acetylcholine, the transmitter agent released at the neuromuscular junctions in the lung. Anticholinergics prevent the increases in intracellular concentration of Ca2+ which is caused by interaction of acetylcholine with the muscarinic receptors on bronchial smooth muscle.

Isoproterenol (trade names Medihaler-Iso and Isuprel) is a medication used for the treatment of bradycardia (slow heart rate), heart block, and rarely for asthma. Isoproterenol is a non-selective β adrenoreceptor agonist and TAAR1 agonist that is the isopropylaminomethyl analog of epinephrine. Isoprenaline's effects on the cardiovascular system (non-selective) relate to its actions on cardiac β1 receptors and β2 receptors on smooth muscle within the tunica media of arterioles. Isoprenaline has positive inotropic and chronotropic effects on the heart. β2 adrenoceptor stimulation in arteriolar smooth muscle induces vasodilation. Its inotropic and chronotropic effects elevate systolic blood pressure, while its vasodilatory effects tend to lower diastolic blood pressure. The overall effect is to decrease mean arterial pressure due to the β2 receptors' vasodilation. The adverse effects of isoprenaline are also related to the drug's cardiovascular effects. Isoprenaline can produce tachycardia (an elevated heart rate), which predisposes patients to cardiac arrhythmias.

Phenobarbital is a barbiturate derivative used to treat insomnia and anxiety, seizures, hyperbilirubinemia in neonates and cholestasis. Phenobarbital promotes binding to inhibitory gamma-aminobutyric acid subtype receptors, and modulates chloride currents through receptor channels.

Racepinephrine or racemic epinephrine is a mixture of levo and dextro isomers of epinephrine act as a nonselective agonist at adrenergic receptors. It is a bronchodilator used in the temporary relief of mild symptoms of intermittent asthma including wheezing, shortness of breath. Inhaled racepinephrine became available in September 2012 as a nonprescription treatment for bronchospasm based on a 1986 US Food and Drug Administration rule. Besides, racemic epinephrine relieves respiratory distress in hospitalized infants with bronchiolitis and is safe but does not abbreviate hospital stay. Morbidity associated with bronchiolitis as identified by parents persists for at least one week after hospital discharge in most infants.

Racephedrine in combination with theophylline, phenobarbital was used to treat bronchial asthma. However, its application was substituted more effective agent. In addition, FDA has reviewed the final monograph for over-the-counter bronchodilator drug products to add additional warnings and to revise the indications in the labeling of products containing racephedrine hydrochloride.

Pseudoephedrine is a sympathomimetic drug. Pseudoephedrine acts as an adrenomimetic and inhibitor of monoamine transporters. Ephedra sinica, a species of ephedra (ma huang), contains ephedrine and pseudoephedrine. Ephedra has been found to stimulate the nervous system, increase airflow into the lungs and constrict blood vessels. In combination with caffeine, ephedra appears to cause weight loss. Pseudoephedrine is a decongestant that shrinks blood vessels in the nasal passages. Pseudoephedrine is used to relieve nasal or sinus congestion caused by the common cold, sinusitis, and hay fever and other respiratory allergies.