- 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.