Serial FEV 1 (shown in Figure 1, below, as means adjusted for center and baseline effects on test day 1 and test day 85 (primary endpoint)) demonstrated that 1 dose (2 inhalations/21 mcg each) of ATROVENT HFA produced significantly greater improvement in pulmonary function than placebo. During the six hours immediately post-dose on day 1, the average hourly improvement in adjusted mean FEV 1 was liters for ATROVENT HFA (42 mcg) and liters for placebo. The mean peak improvement in FEV 1 , relative to baseline, was liters, compared to liters for placebo. During the six hours immediately post-dose on day 85, the average hourly improvement in adjusted mean FEV 1 was liters for ATROVENT HFA (42 mcg) and liters for placebo. The mean peak improvement in FEV 1 , relative to baseline, was liters, compared to liters for placebo.
Ipratropium exhibits broncholytic action by reducing cholinergic influence on the bronchial musculature. It blocks muscarinic acetylcholine receptors, without specificity for subtypes, and therefore promotes the degradation of cyclic guanosine monophosphate (cGMP), resulting in a decreased intracellular concentration of cGMP.  Most likely due to actions of cGMP on intracellular calcium, this results in decreased contractility of smooth muscle in the lung, inhibiting bronchoconstriction and mucus secretion . It is a nonselective muscarinic antagonist ,  and does not diffuse into the blood, which prevents systemic side effects. Ipratropium is a derivative of atropine  but is a quaternary amine and therefore does not cross the blood–brain barrier , which prevents central side effects (anticholinergic syndrome). Ipratropium is not considered a short-acting bronchodilator and should never be used in place of salbutamol (albuterol) as a rescue medication.
Acute overdosage by intranasal administration is unlikely since ipratropium bromide is not well absorbed systemically after intranasal or oral administration. Following administration of a 20 mg oral dose (equivalent to ingesting more than two bottles of Atrovent® (ipratropium bromide) Nasal Spray %) to 10 male volunteers, no change in heart rate or blood pressure was noted. Following a 2 mg intravenous infusion over 15 minutes to the same 10 male volunteers, plasma ipratropium concentrations of 22-45 ng/mL were observed (>100 times the concentrations observed following intranasal administration). Following intravenous infusion these 10 volunteers had a mean increase of heart rate of 50 bpm and less than 20 mmHg change in systolic or diastolic blood pressure at the time of peak ipratropium levels.