- Inability or unwillingness to stop using drugs that may inhibit the ability to treat a severe allergic adverse event. This includes, but is not limited to: beta blockers such as atenolol (Tenormin), metoprolol (Lopressor, Toprol-XL) and propranolol (Inderal, Inderal LA) for 14 days prior to Study Day 0 and for the duration of the study