Atrovent HFA (Ipratropium Bromide) - Description and Clinical Pharmacology

ATTENTION PHARMACIST: Detach "Patient's Instructions for Use" from package insert and dispense with the product.

For Oral Inhalation Only

Prescribing Information

DESCRIPTION

The active ingredient in ATROVENT HFA Inhalation Aerosol is ipratropium bromide (as the monohydrate). It is an anticholinergic bronchodilator chemically described as 8-azoniabicyclo[3.2.1]octane, 3-(3-hydroxy-1-oxo-2-phenylpropoxy)-8-methyl-8-(1-methylethyl)-,bromide monohydrate, (3-endo, 8-syn)-: a synthetic quaternary ammonium compound, chemically related to atropine. The structural formula for ipratropium bromide is:

C₂₀H₃₀BrNO₃•H₂O                ipratropium bromide                Mol. Wt. 430.4

Ipratropium bromide is a white to off-white crystalline substance, freely soluble in water and methanol, sparingly soluble in ethanol, and insoluble in lipophilic solvents such as ether, chloroform, and fluorocarbons.

ATROVENT HFA Inhalation Aerosol is a pressurized metered-dose aerosol unit for oral inhalation that contains a solution of ipratropium bromide. The 200 inhalation unit has a net weight of 12.9 grams. After priming, each actuation of the inhaler delivers 21 mcg of ipratropium bromide from the valve in 56 mg of solution and delivers 17 mcg of ipratropium bromide from the mouthpiece. The actual amount of drug delivered to the lung may depend on patient factors, such as the coordination between the actuation of the device and inspiration through the delivery system. The excipients are HFA-134a (1,1,1,2-tetrafluoroethane) as propellant, sterile water, dehydrated alcohol, and anhydrous citric acid. This product does not contain chlorofluorocarbons (CFCs) as propellants.

Atrovent^® HFA (ipratropium bromide HFA) Inhalation Aerosol should be primed before using for the first time by releasing 2 test sprays into the air away from the face. In cases where the inhaler has not been used for more than 3 days, prime the inhaler again by releasing 2 test sprays into the air away from the face.

CLINICAL PHARMACOLOGY

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. Anticholinergics prevent the increases in intracellular concentration of Ca++ which is caused by interaction of acetylcholine with the muscarinic receptors on bronchial smooth muscle.

Pharmacodynamic Properties

Controlled clinical studies have demonstrated that Atrovent^® (ipratropium bromide) Inhalation Aerosol CFC does not alter either mucociliary clearance or the volume or viscosity of respiratory secretions.

Pharmacokinetics

Most of an administered dose is swallowed as shown by fecal excretion studies. Ipratropium bromide is a quaternary amine. It is not readily absorbed into the systemic circulation either from the surface of the lung or from the gastrointestinal tract as confirmed by blood level and renal excretion studies.

Autoradiographic studies in rats have shown that ipratropium bromide does not penetrate the blood-brain barrier. The half-life of elimination is about 2 hours after inhalation or intravenous administration. Ipratropium bromide is minimally bound (0 to 9% in vitro ) to plasma albumin and α₁-acid glycoprotein. It is partially metabolized to inactive ester hydrolysis products. Following intravenous administration, approximately one-half of the dose is excreted unchanged in the urine.

A pharmacokinetic study with 29 chronic obstructive pulmonary disease (COPD) patients (48-79 years of age) demonstrated that mean peak plasma ipratropium concentrations of 59±20 pg/mL were obtained following a single administration of 4 inhalations of ATROVENT HFA Inhalation Aerosol (84 mcg). Plasma ipratropium concentrations rapidly declined to 24±15 pg/mL by six hours. When these patients were administered 4 inhalations QID (16 inhalations/day=336 mcg) for one week, the mean peak plasma ipratropium concentration increased to 82±39 pg/mL with a trough (6 hour) concentration of 28±12 pg/mL at steady state.

Special Populations

Geriatric Patients

In the pharmacokinetic study with 29 COPD patients, a subset of 14 patients were > 65 years of age. Mean peak plasma ipratropium concentrations of 56±24 pg/mL were obtained following a single administration of 4 inhalations (21 mcg/puff) of Atrovent^® HFA (ipratropium bromide HFA) Inhalation Aerosol (84 mcg). When these 14 patients were administered 4 inhalations QID (16 inhalations/day) for one week, the mean peak plasma ipratropium concentration only increased to 84±50 pg/mL indicating that the pharmacokinetic behavior of ipratropium bromide in the geriatric population is consistent with younger patients.

Renally Impaired Patients

The pharmacokinetics of ATROVENT HFA Inhalation Aerosol have not been studied in patients with renal insufficiency.

Hepatically Impaired Patients

The pharmacokinetics of ATROVENT HFA Inhalation Aerosol have not been studied in patients with hepatic insufficiency.

CLINICAL STUDIES

Conclusions regarding the efficacy of ATROVENT HFA Inhalation Aerosol were derived from two randomized, double-blind, controlled clinical studies. These studies enrolled males and females ages 40 years and older, with a history of COPD, a smoking history of > 10 pack- years, an FEV₁ < 65% and an FEV₁/FVC < 70%.

One of the studies was a 12-week randomized, double-blind active and placebo controlled study in which 505 of the 507 randomized COPD patients were evaluated for the safety and efficacy of 42 mcg (n=124) and 84 mcg (n=126) ATROVENT HFA Inhalation Aerosol in comparison to 42 mcg (n=127) Atrovent® (ipratropium bromide) Inhalation Aerosol CFC and their respective placebos (HFA n=62, CFC n=66). Data for both placebo HFA and placebo CFC were combined in the evaluation.

Serial FEV₁ (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 Inhalation Aerosol 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 FEV₁ was 0.148 liters for ATROVENT HFA Inhalation Aerosol (42 mcg) and 0.013 liters for placebo. The mean peak improvement in FEV₁, relative to baseline, was 0.295 liters, compared to 0.138 liters for placebo. During the six hours immediately post-dose on day 85, the average hourly improvement in adjusted mean FEV₁ was 0.141 liters for ATROVENT HFA Inhalation Aerosol (42 mcg) and 0.014 liters for placebo. The mean peak improvement in FEV₁, relative to baseline, was 0.295 liters, compared to 0.140 liters for placebo.

ATROVENT HFA Inhalation Aerosol (42 mcg) was shown to be clinically comparable to ATROVENT Inhalation Aerosol CFC (42 mcg).

Figure 1 Day 1 and Day 85 (Primary Endpoint) Results

In this study, both Atrovent® HFA (ipratropium bromide HFA) Inhalation Aerosol and Atrovent® (ipratropium bromide) Inhalation Aerosol CFC formulations were equally effective in patients over 65 years of age and under 65 years of age.

The median time to improvement in pulmonary function (FEV₁ increase of 15% or more) was within approximately 15 minutes, reached a peak in 1-2 hours, and persisted for 2 to 4 hours in the majority of the patients. Improvements in Forced Vital Capacity (FVC) were also demonstrated.

The other study was a 12-week, randomized, double-blind, active-controlled clinical study in 174 adults with COPD, in which ATROVENT HFA Inhalation Aerosol 42 mcg (n=118) was compared to ATROVENT Inhalation Aerosol CFC 42 mcg (n=56). Safety and efficacy of HFA and CFC formulations were shown to be comparable.

The bronchodilatory efficacy and comparability of Atrovent® HFA (ipratropium bromide HFA) Inhalation Aerosol vs. Atrovent® (ipratropium bromide) Inhalation Aerosol CFC were also studied in a one-year open-label safety and efficacy study in 456 COPD patients. The safety and efficacy of HFA and CFC formulations were shown to be comparable.