Mechanism of Action

Ipratropium bromide is an anticholinergic (parasympatholytic) agent which, based on animal studies, appears to inhibit vagally-mediated reflexes by antagonizing the action of acetylcholine, the transmitter agent released at the neuromuscular junctions in the lung. In humans, ipratropium bromide has anti-secretory properties and, when applied locally, inhibits secretions from the serous and seromucous glands lining the nasal mucosa. Ipratropium bromide is a quaternary amine that minimally crosses the nasal and gastrointestinal membranes and the blood-brain barrier, resulting in a reduction of the systemic anticholinergic effects (e.g., neurologic, ophthalmic, cardiovascular, and gastrointestinal effects) that are seen with tertiary anticholinergic amines.

Pharmacokinetics

Absorption: Ipratropium bromide is poorly absorbed into the systemic circulation following oral administration (2% to 3%). Less than 20% of an 84 mcg per nostril dose was absorbed from the nasal mucosa of normal volunteers, induced-cold adult volunteers, naturally acquired common cold pediatric patients, or perennial rhinitis adult patients. 

Distribution: Ipratropium bromide is minimally bound (0% to 9% in vitro) to plasma albumin and α1-acid glycoprotein. Its blood/plasma concentration ratio was estimated to be about 0.89. Studies in rats have shown that ipratropium bromide does not penetrate the blood-brain barrier.

Metabolism: Ipratropium bromide is partially metabolized to ester hydrolysis products, tropic acid, and tropane. These metabolites appear to be inactive based on in vitro receptor affinity studies using rat brain tissue homogenates.

Elimination: After intravenous administration of 2 mg ipratropium bromide to 10 healthy volunteers, the terminal half-life of ipratropium bromide was approximately 1.6 hours. The total body clearance and renal clearance were estimated to be 2,505 and 1,019 mL/min, respectively. The amount of the total dose excreted unchanged in the urine (Ae) within 24 hours was approximately one-half of the administered dose.

Pediatrics: Following administration of 84 mcg of ipratropium bromide per nostril three times a day in patients 5 to 18 years old (n=42) with a naturally acquired common cold, the mean amount of the total dose excreted unchanged in the urine of 7.8% was comparable to 84 mcg per nostril four times a day in an adult induced common cold population (n=22) of 7.3% to 8.1%. Plasma ipratropium concentrations were relatively low (ranging from undetectable up to 0.62 ng/mL). No correlation of the amount of the total dose excreted unchanged in the urine (Ae) with age or gender was observed in the pediatric population.

Special Populations: Gender does not appear to influence the absorption or excretion of nasally administered ipratropium bromide. The pharmacokinetics of ipratropium bromide have not been studied in patients with hepatic or renal insufficiency or in the elderly.

Drug-Drug Interactions: No specific pharmacokinetic studies were conducted to evaluate potential drug-drug interactions.

Pharmacodynamics

In two single dose trials (n=17), doses up to 336 mcg of ipratropium bromide did not significantly affect pupillary diameter, heart rate, or systolic/diastolic blood pressure. Similarly, Ipratropium Bromide Nasal Solution 0.06% in adult patients (n=22) with induced-colds (84 mcg/nostril four times a day) and in pediatric patients (n=45) with naturally acquired common cold (84 mcg/nostril three times a day) had no significant effects on pupillary diameter, heart rate, or systolic/diastolic blood pressure.

Controlled clinical trials demonstrated that intranasal fluorocarbon-propelled ipratropium bromide does not alter physiologic nasal functions (e.g., sense of smell, ciliary beat frequency, mucociliary clearance, or the air conditioning capacity of the nose).

Clinical Trials

Clinical trials for Ipratropium Bromide Nasal Solution 0.06% were conducted in patients with rhinorrhea associated with naturally occurring common colds. In two controlled four day comparisons of Ipratropium Bromide Nasal Solution 0.06% (84 mcg per nostril, administered three or four times daily; n=352) with its vehicle (n=351), there was a statistically significant reduction of rhinorrhea, as measured by both nasal discharge weight and the patients’ subjective assessment of severity of rhinorrhea using a visual analog scale. These significant differences were evident within one hour following dosing. There was no effect of Ipratropium Bromide Nasal Solution 0.06% on degree of nasal congestion or sneezing. The response to Ipratropium Bromide Nasal Solution 0.06% did not appear to be affected by age or gender. No controlled clinical trials directly compared the efficacy of three times daily versus four times daily treatment.

One clinical trial was conducted with Ipratropium Bromide Nasal Solution 0.06%, administered four times daily for three weeks, in 218 patients with rhinorrhea associated with Seasonal Allergic Rhinitis (SAR), compared to its vehicle in 211 patients. Patients in this trial were adults and adolescents 12 years of age and above. Ipratropium Bromide Nasal Solution0.06% was significantly more effective in reducing the severity and duration of rhinorrhea over the three weeks of the study, as measured by daily patient symptom scores. There was no difference between treatment groups in the effect on nasal congestion, sneezing or itching eyes.