 Treatment T Albuterol-HFA, N200: 216 mcg albuterol sulfate equivalent to 180 mcg albuterol base, QID; Treatment R Proventil-HFA, N50: 216 mcg albuterol sulfate equivalent to 180 mcg albuterol base, QID; Treatment P Placebo-HFA, N50: two actuations of placebo, QID. 