- Concomitant medications: Administration of prescription or over the counter medication that would significantly affect the course of asthma, or interact with study treatment, such as: anticonvulsants (barbiturates, hydantoins, carbamazepine); polycyclic antidepressants; beta-adrenergic blocking agents; phenothiazines; and monoamine oxidase (MAO) inhibitors; Immunosuppressive medications: A subject must not be using or require use of immunosuppressive medications during the study; cytochrome P450 3A4 (CYP3A4) inhibitors: Subjects who have received a potent CYP3A4 inhibitor within 4 weeks of Visit 1(Screening and Run-in Visit) (e.g., ritonavir, ketoconazole, itraconazole) ; Unable to refrain from the use of prescription or nonprescription drugs, including vitamins, herbal and dietary supplements (including St John's wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or five half-lives (whichever is longer) before the first dose of study treatment, unless in the opinion of the investigator and medical monitor the medication will not interfere with the study procedures or compromise subject safety; Any subjects that have previously received or are currently receiving omalizumab .